New and expectant parents often have questions related to vaccines as this period of life typically involves conversations and decisions related to vaccines. Expectant parents, their babies, and even those who will be around their babies, may need vaccines.

In some cases, vaccines protect the individual who is pregnant as the changes related to pregnancy make them more susceptible to infections, but in other cases, the vaccines are meant to protect the baby. Questions sometimes relate to special circumstances, such as vaccinating after a premature birth or during breastfeeding, or they pertain to the vaccination of other children in the home.

The information below addresses these issues. If you can’t find the answer to your question, please contact us online so we can help you.

Vaccines, the immune system and pregnancy

During pregnancy, two changes related to the immune system can make individuals more susceptible to certain infections:

• Suppressed immune system function — Because the growing fetus is not genetically identical, the body has to undergo changes during pregnancy so that it does not “reject” or “attack” the fetus as a foreign entity. As a result, during pregnancy, the immune system is less efficient, making the individual more susceptible to infections than someone of their age who is not pregnant.
• Physical changes — As the pregnancy progresses, increased fluid volume adds stress to the heart and lungs. This makes individuals more susceptible to respiratory infections, particularly influenza and COVID-19, compared to non-pregnant people of the same age.

These changes can also make pregnant people more likely to experience severe disease compared with someone of the same age who is not pregnant. As such, some vaccines given during pregnancy protect the baby but are primarily recommended to protect the pregnant individual. Examples are the influenza and COVID-19 vaccines. On the other hand, sometimes vaccines are given for the primary purpose of protecting the baby by exposing them to maternal antibodies that can offer protection until the baby generates their own immunity or is at an age when they are less susceptible to severe disease if infected. Vaccines given to protect the baby include the RSV and Tdap vaccines, the latter of which protects against pertussis. 

Read more about pregnancy and immunity in this Q&A.

Important vaccines during pregnancy

• Influenza. While influenza vaccine is recommended for everyone, those who will be pregnant during influenza season should receive the inactivated flu vaccine (flu shot). Pregnant people are at increased risk for influenza-related complications that require hospitalization. The influenza vaccine also protects the baby in the first few months of life before they can get vaccinated. As such, those in their third trimester during late summer or early fall should try to get vaccinated against influenza a few weeks before delivery if the vaccine for the upcoming season is available, so the baby will benefit from maternal antibodies. Those who will be pregnant during influenza season should also make sure they are immunized before influenza starts circulating in their community.
• COVID-19. Individuals who are infected with COVID-19 during pregnancy are at increased risk for complications, compared with similarly aged people who are not pregnant. Due to this risk, pregnant people should follow current recommendations for COVID-19 vaccination. 
• Hepatitis B. Because many people do not know that they are infected with hepatitis B virus, and because an infant can be exposed to the virus during delivery, your obstetrician will perform a blood test to determine whether you are infected with hepatitis B. If you are infected, your baby will be vaccinated and given an antibody preparation shortly after birth to prevent them from getting the disease.
• Tdap. A dose of Tdap should be administered between 27 and 36 weeks of gestation during each pregnancy for the newborn to have protection against pertussis, or whooping cough. While anytime during this window is fine, public health officials suggest getting this vaccine earlier rather than later. Those who did not receive the vaccine during pregnancy should get it immediately after giving birth, so they are less likely to get pertussis and pass it to their newborn.
• Pneumococcal. Those considered high risk for pneumococcal disease should get pneumococcal vaccine if they have not had it. High-risk conditions include chronic disorders of the pulmonary system (but not asthma), cardiovascular disease, diabetes mellitus, chronic liver diseases, chronic renal failure, asplenia (including sickle cell disease), immunosuppressive conditions (i.e., HIV, leukemia, lymphoma, multiple myeloma, Hodgkin disease, generalized malignancy, or organ or bone marrow transplantation), cigarette smoking, alcoholism, cerebrospinal fluid (CSF) leak, treatment with certain medications, or cochlear implants. Talk with your doctor if you are not sure whether you are considered high risk.
• Respiratory syncytial virus (RSV). Individuals who will deliver during RSV season may be offered one dose of RSV vaccine (Abrysvo) from 32 through 36 weeks of gestation. In most parts of the United States, the vaccine will be given to those who reach this period of pregnancy from September through January. However, the precise seasonal recommendation may differ based on the spread of the virus in their area during each season. This vaccination aims to protect the baby immediately after birth due to the increased risk of severe RSV disease and hospitalization in young infants. This protection, known as passive immunization, allows the infant to benefit from the maternal antibodies that cross the placenta and are delivered in breast milk after vaccination. If a pregnant person does not receive the RSV vaccine or is not eligible to receive it because of the seasonality of the recommendation (or because they have had the vaccine previously), the newborn baby can get a monoclonal antibody product, called Beyfortus, shortly after birth. To find out more about the considerations for getting vaccinated during pregnancy or having the baby immunized after birth, check our Q&A, “Protecting Babies from RSV: What You Should Know.” (English | Spanish)

Vaccines to avoid during pregnancy

• MMR. Live, weakened viral vaccines, including the ones for measles, mumps and rubella (MMR) should generally be avoided during pregnancy due to a theoretical risk of viral replication that could affect the developing fetus. Likewise, pregnancy should be avoided for four weeks after receipt of the MMR vaccine. See “Important note” below.
• Varicella (chickenpox). As with MMR, this vaccine contains a live, weakened virus and should not be given during pregnancy. Additionally, pregnancy should be avoided for at least four weeks after receipt of chickenpox vaccine. See “Important note” below.
• HPV. Those who have started the HPV vaccine series before becoming pregnant should wait until after delivery to get the remaining doses. See “Important note” below if you receive this vaccine during pregnancy.

Important note: If you inadvertently receive any of these vaccines during pregnancy, you should be aware that none have been proven to be harmful to your unborn baby. The recommendation to avoid these vaccines is theoretical. In some cases, databases are maintained by the manufacturers to track these occurrences. For example, if you receive the HPV vaccine during pregnancy, you can contact the manufacturer with questions or report the dose by calling 877-888-4231.

People in the home of someone who is pregnant

Children and adults living in the home of someone who is pregnant can receive all recommended vaccines.

Are you on Pinterest?

The VEC curated a Pinterest board that includes a collection of VEC resources that may be of interest during pregnancy.

Breastfeeding

Baby

Infants who are being breastfed may receive all routinely recommended vaccines for infants. Antibodies in breast milk do not interfere with any of the currently recommended vaccines.

Sometimes parents wonder whether they can forego immunizations for their baby because the baby is being breastfed; however, this is not the best decision since antibodies in human breast milk bathe the intestinal surface but are not absorbed. Therefore, breast milk antibodies never enter the bloodstream where they would be needed to protect against certain diseases. Examples of these types of diseases include diphtheria, tetanus, pertussis; measles, mumps, rubella; varicella (chickenpox); pneumococcus; Haemophilus influenzae type b; polio; hepatitis A and hepatitis B.

Vaccines while breastfeeding

Parents who are breastfeeding can receive any vaccines they need during this time, including the COVID-19 vaccine. Although some live viral vaccines may replicate and cause viruses to be excreted in breast milk, the viruses are weakened sufficiently that they will not harm the baby.

In most cases, live viral vaccines (specifically, MMR and chickenpox) are recommended prior to becoming pregnant because the diseases they prevent may be harmful to a developing fetus if infected during pregnancy; however, they can be given while breastfeeding if needed.

Preterm infants

Any baby born before the 37th week of pregnancy is considered to be preterm. Find answers to vaccine-related questions for preterm babies.

Vaccines: Birth to 2 years of age

For questions related to the vaccines your baby is recommended to receive in the months after birth, the following resources are available:

• Informational booklets — The VEC offers two booklets, “Vaccines and Your Baby” (also available in Spanish) and “Vaccine Safety and Your Family: Separating Fact from Fiction” (also available in Spanish) for any new parent(s) looking for more information about vaccines.
• Vaccine videos — The VEC offers a variety of videos that address common vaccine-related questions. Review this page of our website for more information.
• Q&A sheets related to vaccine and vaccine safety — These question-and-answer sheets address a variety of topics related to vaccines and vaccine safety in an easy-to-read format. A series of “Special Topics” Q&As are also available to address additional, related concerns.

Choosing a doctor for your children

Choosing a doctor for your children is one of the most important decisions new parents make. That doctor, or practice, is essentially a co-pilot helping you care for the health, development and well-being of your child, while empowering you, as the pilot, to make healthy decisions for your family. In short, choosing a physician is no small task.

So, how can you pick the right co-pilot for your growing family’s health needs? One way you can evaluate a specific practice’s potential fit for your family is to evaluate their views and approach to a variety of topics you know will come up. Because vaccines are a universal part of newborn, infant and early childhood visits, the topic of vaccines can serve as a good barometer for several reasons.

1. Vaccines are a topic that will come up quickly since the hepatitis B vaccine is recommended within 24 hours of birth.
2. Vaccines will come up often. During the first year of life, almost every visit will include a conversation about vaccines.
3. Vaccines are often a topic you may already have questions about. So, discussing them during the process of choosing a provider helps you to see how they answer questions, what sources of information they provide as resources, and how they tend to communicate. Are questions readily answered? Are the answers presented in a way that you understand? Are additional resources provided?

For these reasons, vaccine conversations are a great opportunity to get familiar with a healthcare provider and his or her practice style.

Yet, even as you have these conversations, you may still have some vaccine-related concerns. Healthcare providers understand this, and most of them try to answer your questions and help you be more comfortable with one of the most emotional aspects of new parenthood. Unfortunately, in an attempt to placate parents’ concerns, a healthcare provider may offer an “alternative” immunization schedule to replace the immunization schedule recommended by the Centers for Disease Control and Prevention (CDC). While this may make a physician seem like a potentially good co-pilot or fit for your family, it may actually be a sign of something else — a doctor who sees themselves as better equipped to make a schedule than groups of experts with a variety of backgrounds and areas of expertise. While this type of “independent” approach may be appealing, parents should proceed with caution for a couple of reasons. First, only the recommended schedule has been tested. Second, it means this provider or office may be willing to stray from collective scientific understanding on other topics as well.

The benefits of vaccinating according to the recommended immunization schedule far outweigh any theoretical risks. Therefore, when speaking to a prospective physician about vaccines, consider the following types of statements to be RED FLAGS TO WATCH FOR:

• Some vaccines are not necessary — Certain “alternative” schedules forego vaccines that the doctor doesn’t deem necessary because the diseases are not rampant in their community. The fact of the matter is, those diseases are no longer present because of vaccines, and maintaining a highly vaccinated population is what keeps them out.
  
  Healthy children who skip those vaccines then rely on protection afforded in the community, essentially relying on other parents to maintain the collective health of the community by vaccinating their children. Said another way, the provider is saying your child is more important than those getting vaccinated. While this may appear favorable to you — a way to protect your child without any “risks” — you should ask yourself what this says about a healthcare provider who is willing to pick and choose which community members should or should not contribute to the health of the community.
• Some vaccines should be delayed or separated because of certain ingredients — This sounds innocent enough, but choosing to do so is abandoning scientific evidence in favor of unfounded fears. The timing of the schedule is designed to protect children from harmful diseases before their risk of disease increases. For example, as maternal antibodies wane, immunizations are timed so that the infant’s own immune protection is developed. That only works if vaccines are given according to the scientifically tested schedule. Further, the ingredients that have been sources of concern related to safety are present in miniscule amounts and have been found to be safe.
  
  Using unscientific changes to an already tested schedule does not provide additional protection. In fact, quite the opposite. It puts children at unnecessary risk while providing superficial placation to ease fear.
• Vaccines are not well tested — Before vaccines are licensed in the U.S., they undergo decades of scientific testing that involves thousands and thousands of study participants. Part of that testing examines how vaccines interact as part of the recommended immunization schedule. Providers who suggest that vaccines are not well tested are essentially admitting how little they know about the process of making vaccines.
  
  The reality is that “alternative” schedules created by individual doctors have not undergone scientific testing. Statements related to their experiences with these schedules in their practices are by definition not controlled studies since they only look at the group of people who tried it. Comparisons with national samples are also not appropriate because they do not account for the variability found in large, diverse populations from different geographic regions.

Yes, being a parent can be scary. Watching your child receive multiple vaccines in the first two years of life, often given several at a time, is unsettling. However, it is your pediatrician’s job to, above all else, have your child’s best interests at heart. Doing so means utilizing all medically safe tools and resources available. It does not mean choosing to assert their own beliefs over medical science in an attempt to assuage fears. The VEC offers a question-and-answer sheet about doctors who make alternative schedules that has more information.

Additional resources

• Recommended Immunization Schedule: What You Should Know – English | Spanish (PDF)
• Too Many Vaccines? What You Should Know – English | Spanish (PDF)  
• Vaccine Ingredients: What You Should Know – English | Spanish (PDF)
• What Is the Harm in Delaying or Spacing out Vaccines? (VIDEO)

Other questions you may have

Can someone who had a live, weakened viral vaccine (e.g., MMR, chickenpox, nasal influenza, rotavirus, or outside of the U.S., oral polio) be near a new baby or a pregnant person?

Yes. Although these vaccines contain live, weakened viruses, recently vaccinated people are not likely to spread the virus after vaccination, with a few exceptions:

• If a person who got the chickenpox vaccine develops a rash, they should take precautions to ensure that the baby, or an unvaccinated pregnant person, does not come into contact with the sores as they may contain the weakened virus and could, theoretically, spread to the unprotected individual.
• Weakened, live polio virus can spread following vaccination; however, the weakened virus typically does not cause disease. In most cases, when unvaccinated people come into contact with polio vaccine virus (from the oral polio vaccine, which is not given in the U.S.), they can get infected and gain immunity without experiencing illness or being vaccinated. This is called contact immunity. On rare occasions, the polio virus in the oral vaccine can revert to its natural form and cause paralytic polio. This happened to an unvaccinated individual in New York in July 2022. Because pregnant individuals typically have immunity against polio, they do not need to take special precautions. Likewise, special precautions are not typically needed for infants in the first few months of life before they are old enough to be vaccinated. However, if more cases of polio develop in the U.S., you may want to limit your baby’s exposure to unvaccinated individuals who recently traveled or have been around others who recently traveled.

What do I need to know about Zika virus and how to avoid it if I am pregnant?

Zika virus is spread through mosquito bites. Most people who are infected do not have any symptoms and a few (about 1 in 5) will have symptoms such as fever, rash, joint pain or pink eye. The most concerning aspects of Zika virus infection during pregnancy are the adverse effects on the developing fetus.

Read the "Zika Virus: What you Should Know" Q&A sheet for more information.

Should medicine be given before a child gets vaccinated to prevent or control fever?

Fevers are actually a sign that the immune system is responding to a challenge. If children are given fever-reducing medications before vaccinations, they may not develop a fever, but their immune response to the vaccines may also be lower.

Read the "Infectious Diseases and Fevers: What You Should Know" Q&A sheet for more information about fevers, what they are, and how to treat them.

Additional resources

Materials developed by the Vaccine Education Center at Children’s Hospital of Philadelphia:

• Infectious Diseases and Pregnancy: What You Should Know — This question-and-answer sheet addresses vaccine and immunity topics relevant during pregnancy.
• Vaccines and Your Baby — This video and booklet series describes vaccines commonly given in the first few years of life and the diseases they prevent. The booklet is also available in Spanish. To watch this or other VEC videos in Spanish, follow the steps in this module, offered courtesy of Immunize Kansas.
• Vaccines on the Go: What You Should Know — This free mobile app is available for iPhone and Android devices. In addition to easily having vaccine information any place you need it, you can email the VEC with questions and view additional resources including Q&A sheets and videos.
• Are Maternal Antibodies Considered When the Vaccine Schedule is Made? — In this video, Dr. Offit talks about how the transfer of maternal antibodies impacts the creation of the vaccine schedule.

References

Pregnancy and infections

Al-Haddad B, Jacobsson B, Chabra S, et al. Long-term risk of neuropsychiatric disease after exposure to infection in utero. JAMA Psychiatry. 2019 Mar 6. doi: 10.1001/jamapsychiatry2019.0029.
In 2019, researchers from the Department of Obstetrics and Gynecology at the University of Washington School of Medicine evaluated the relationship between maternal infections during hospitalization and neuropsychiatric outcome. A total of 1,791,520 Swedish children born between 1973 and 2014 were observed for up to 41 years using linked, population-based registries. Maternal infections while hospitalized during pregnancy included 1) any maternal infection, 2) severe infections such as sepsis, meningitis, encephalitis, pneumonia, influenza, pyelonephritis, or chorioamnionitis, and 3) urinary tract infections.

The authors found that any maternal infection during pregnancy significantly increased the likelihood of diagnosis of autism or depression in their offspring. No evidence was found, however, for an increase in the diagnosis of bipolar disorder or psychosis. The authors concluded “These results emphasize the importance of avoiding infections during pregnancy, which may impart subtle fetal brain injuries contributing to development of autism and depression.”

Pregnancy and vaccines

Hepatitis A vaccine

Groom HC, Smith N, Irving SA, Koppolu P, Vazquez-Benitez G, et al. Uptake and safety of hepatitis A vaccination during pregnancy: a Vaccine Safety Datalink study. Vaccine 2019;37:6648-6655.
The authors evaluated the potential association between maternal hepatitis A vaccination and maternal and infant safety outcomes in more than 1,100 women with live births over an 11-year period. Pregnancies with hepatitis A vaccine exposure were compared to those with other vaccine exposures and to those with no vaccine exposures. Approximately 70% of women received hepatitis A vaccine during the first trimester. There were no significant associations between hepatitis A vaccine exposure during pregnancy and gestational hypertension, gestational diabetes, pre-eclampsia/eclampsia, caesarian-section delivery, preterm delivery, and low birth weight. There was an association between hepatitis A vaccine receipt and delivering an infant who was small for gestational age, but this was likely due to confounding factors.

Panagiotou OA, Befano BL, Rodriguez AC, Herrero R, Schiller JT, et al. Effect of bivalent human papillomavirus vaccination on pregnancy outcomes: long term observational follow-up in the Costa Rica HPV vaccine trial. British Medical Journal 2015;351:h4358.
The authors examined the effect of the bivalent HPV vaccine on miscarriage by comparing women who received HPV vaccine versus those who received either hepatitis A vaccine or no vaccine. The three groups did not differ in their incidence of miscarriage, even after adjusting for age at vaccination and age at conception.

HPV vaccine

Bi D, Apter D, Eriksson T, Hokkanen M, Zima J, et al. Safety of the AS04-adjuvanted human papillomavirus (HPV)-16/18 vaccine in adolescents aged 12-15 years: end-of-study results from a community-randomized study up to 6.5 years. Human Vaccines and Immunotherapy 2019;12:1-12 (epub ahead of print).
In this randomized study, the authors evaluated the efficacy and safety of an adjuvanted-HPV 16/18 vaccine in more than 32,000 Finnish adolescent males and females over a 6.5-year period by comparing those who received HPV vaccine to those who received hepatitis B vaccine. The HPV vaccine adjuvant was composed of monophosphoryl-lipid A plus aluminum salts. The incidence of new-onset autoimmune diseases was similar in both vaccine groups. Similarly, those receiving HPV vaccine during pregnancy did not have an increased risk for spontaneous abortion or congenital anomalies.

Kharbanda EO, Vazquez-Benitez G, Lipkind HS, Sheth SS, Zhu J, et al. Risk of spontaneous abortion after inadvertent human papillomavirus vaccination in pregnancy. Obstet Gynecol 2018;132(1):35-44.
The authors evaluated the risk of spontaneous abortion following quadrivalent HPV vaccination given before and during pregnancy during a 7-year period. No differences in the risk of spontaneous abortion were identified when comparing those who had received vaccine 16 to 22 weeks before their last menstrual period versus those vaccinated either within 6 weeks of last menstrual period or during the first 19 weeks of pregnancy. The authors concluded that HPV vaccine did not increase the risk of spontaneous abortion in the 6 weeks preceding pregnancy or during pregnancy. 

Lipkind HS, Vazquez-Benitez G, Nordin JD, Romitti PA, Naleway AL, et al. Maternal and infant outcomes after human papillomavirus vaccination in the periconceptional period or during pregnancy. Obstet Gynecol 2017;130(3):599-608.
The authors evaluated whether quadrivalent HPV vaccine administered during the periconceptional period or during pregnancy was associated with increased risks for adverse outcomes. The authors compared outcomes between those women vaccinated two weeks before or two weeks after their last menstrual period with women who were vaccinated four to 18 months before their last menstrual period. Administration of quadrivalent HPV vaccine in the periconceptional period or during pregnancy was not associated with an increased risk of preterm delivery, small for gestational age, chorioamnionitis, hypertensive disorders of pregnancy and gestational diabetes, or more than 50 selected major structural birth defects.

Scheller NM, Pasternak B, Molgaard-Nielsen D, Svanstrom H, Hviid A. Quadrivalent HPV vaccination and the risk of adverse pregnancy outcomes. N Engl J Med 2017;376(13):1223-1233.
The authors assessed the risk of adverse pregnancy outcomes after quadrivalent HPV vaccine exposure during pregnancy in Danish women. Exposure to the quadrivalent HPV vaccine was not associated with significantly higher risks for major birth defect, spontaneous abortion, preterm birth, low birth weight, small for gestational age, or still birth.

Moreira ED, Block SL, Ferris D, Giuliano AR, Iversen OE, et al. Safety profile of the 9-valent HPV vaccine: a combined analysis of 7 phase III clinical trials. Pediatrics 2016;138(2):e20154387.
The authors evaluated the safety profile of the 9-valent HPV vaccine in seven phase III studies. Pregnancy outcomes, including those among live births through the first six weeks of life, were analyzed among nearly 3,000 pregnancies that occurred during the study period. The incidence of adverse pregnancy outcomes was compared between quadrivalent HPV and 9-valent HPV vaccines. The authors found no difference in the number of fetal losses (e.g., spontaneous abortion, late fetal death, etc.), or the incidence of congenital anomalies between the groups. Additionally, the proportion of pregnancies with adverse outcome were within ranges reported in the general population. 

Baril L, Rosillon D, Willame C, Angelo MG, Zima J, et al. Risk of spontaneous abortion and other pregnancy outcomes in 15-25 year old women exposed to human papillomavirus-16/18 AS04-adjuvanted vaccine in the United Kingdom. Vaccine 2015;33:6884-6891.
The authors assessed the risk of spontaneous abortion and other adverse pregnancy outcomes after inadvertent exposure to HPV-16/18 vaccine surrounding gestation during a three-year period.  Investigators found no increased risk of spontaneous abortion, still birth, preterm or post-term birth, small or large for gestational age, or infant death before 12 weeks when comparing those women who became pregnant within 30 days before or 45 to 90 days after vaccine receipt versus those who became pregnant 120 days to 18 months after the last HPV vaccine dose. 

Panagiotou OA, Befano BL, Rodriguez AC, Herrero R, Schiller JT, et al. Effect of bivalent human papillomavirus vaccination on pregnancy outcomes: long term observational follow-up in the Costa Rica HPV vaccine trial. BMJ 2015;351:h4358.
The authors examined the effect of the bivalent HPV vaccine on miscarriage by comparing women who received HPV vaccine, hepatitis A vaccine, or no vaccine. The three groups did not differ in their incidence of miscarriage after adjusting for age at vaccination and age at conception.

Wacholder S, Chen BE, Wilcox A, Macones G, Gonzalez P, et al. Risk of miscarriage with bivalent vaccine against human papillomavirus (HPV) types 16 and 18: pooled analysis of two randomized controlled trials. BMJ 2010;340:c712.
The authors evaluated the risk of miscarriage after receipt of AS04-adjuvanted bivalent 16/18 HPV vaccine during pregnancy. More than 3,500 pregnancies occurred in the two multicenter phase III trials where the bivalent vaccine was compared to a control group that received hepatitis A vaccine. No differences in the rate of miscarriage were detected between the two groups.

Garland SM, Ault KA, Gall SA, Paavonen J, Sings HL, et al. Pregnancy and infant outcomes in the clinical trials of a human papillomavirus type 6/11/16/18 vaccine: a combined analysis of five randomized controlled trials. Obstet Gynecol 2009;114(6):1179-1188.
The authors analyzed the outcomes of more than 4,000 pregnancies in women who did or did not receive the quadrivalent HPV vaccine. No significant differences were detected between the two groups regarding the proportion of pregnancies resulting in live birth, fetal loss, spontaneous abortion, and congenital anomalies.

Tetanus, diphtheria, and acellular pertussis vaccines

Tavares F, Nazareth I, Monegal JS, Kolte I, Verstraeten T, et al. Pregnancy and safety outcomes in women vaccinated with an AS03-adjuvanted split virion H1N1 (2009) pandemic influenza vaccine during pregnancy: a prospective cohort study. Vaccine 2011;29:6358-6365.
In this prospective, observational study, the authors found that receipt of the AS03-adjuvanted H1N1 pandemic influenza vaccine administered during pregnancy was not associated with an increased risk of spontaneous abortion, stillbirth, congenital anomalies, preterm delivery, low birth weight, or maternal complications including upper respiratory tract infection, urinary tract infection and preeclampsia/hypertension.

Omon E, Damase-Michel C, Hurault-Delarue C, Lacroix I, Montastruc JL, et al. Non-adjuvanted 2009 influenza A (H1N1)v vaccine in pregnant women: the results of a French prospective descriptive study. Vaccine 2011;29:9649-9654.
In this prospective, observational study, the authors described pregnancy outcomes among more than 500 French women who were vaccinated with non-adjuvanted influenza A/H1N1 vaccines. Compared with the general population, vaccination during pregnancy was not associated with an increased risk of maternal complications (e.g., preterm labor, hypertension, gestational diabetes, premature rupture of membranes, infections), congenital malformations (e.g., orthopedic, renal, genital, cardiologic, ophthalmologic, otologic, among others) or other neonatal disorders (e.g., quadriplegia, hearing impairment, respiratory infection, infectious diseases, among others).

Pasternak B, Svanstrom H, Molgaard-Nielsen D, Krause TG, Emborg HD, et al. Risk of adverse fetal outcomes following administration of a pandemic influenza A (H1N1) vaccine during pregnancy. JAMA 2012;308(2):165-174.
The authors investigated the incidence of adverse fetal outcomes in 7000 Danish women who did or did not receive an adjuvanted influenza A(H1N1)pdm09 vaccine during pregnancy. Exposure to the vaccine, regardless of trimester, was not associated with a significantly increased risk of major birth defects, preterm birth, or fetal growth restriction.

Oppermann M, Fritzsche J, Weber-Schoendorfer C, Keller-Stanislawski B, Allignol A, et al. A(H1N1)v2009: a controlled observational prospective cohort study on vaccine safety in pregnancy. Vaccine 2012;30:4445-4452.
The authors assessed the safety of influenza A/H1N1 vaccination in pregnancy by prospectively following the pregnancies of German women who were vaccinated during pregnancy or ≤ 4 weeks prior to conception and comparing outcomes to unvaccinated pregnant women. The authors found no differences in the risks for spontaneous abortions, preeclampsia, prematurity, or intrauterine growth restriction, or a difference in the rate of major malformations in women who were vaccinated compared with unvaccinated women.

Launay O, Krivine A, Charlier C, Truster V, Tsatsaris V, et al. Low rate of pandemic A/H1N1 2009 influenza infection and lack of severe complication of vaccination in pregnant women: a prospective cohort study. PLoS ONE 2012;7(12):e52303.
In this prospective cohort study, the authors assessed the consequences of maternal receipt of pandemic A/H1N1 2009 influenza on pregnancy outcomes by comparing vaccinated to unvaccinated women. They found no significant difference in pregnancy outcomes (i.e., onset of labor, mode of delivery, gestational age at delivery) and perinatal outcomes (i.e., birth weight, Apgar score, or requirement for neonatal intensive care) between women who received A/H1N1 2009 influenza vaccine and those who didn’t.

Rubinstein F, Bonotti A, Wainer V, Schwarcz A, Augustovski F, et al. Influenza A/H1N1 MF59-adjuvanted vaccine in pregnant women and adverse perinatal outcomes: multicenter study. BMJ 2013;346:f393.
In this multicenter, prospective study, the authors evaluated the risk of adverse perinatal events after vaccination with an MF59-adjuvanted influenza A/H1N1 vaccine in more than 7200 pregnant women. Vaccinated pregnant women were found to have a lower risk of low birthweight, preterm delivery, or fetal or early neonatal death up to seven days postpartum when compared to unvaccinated pregnant women.

Chavant F, Ingrand I, Jonville-Bera AP, Plazanet C, Gras-Champel V, et al. The PREGVAXGRIP study: a cohort study to assess foetal and neonatal consequences of in utero exposure to vaccination against A(H1N1)v2009 influenza. Drug Saf 2013;36:455-465.
In this prospective study, the authors assessed the outcomes of more than 2400 pregnant French women who received the 2009 influenza A/H1N1 pandemic vaccine.  The rate of congenital malformations, spontaneous abortions, still births, preterm deliveries, or neonatal disorders was not higher than the rate reported in the general population.

Chambers CD, Johnson D, Xu R, Luo Y, Louik C, et al. Risks and safety of pandemic H1N1 influenza vaccine in pregnancy: birth defects, spontaneous abortion, preterm delivery and small for gestational age infants. Vaccine 2013;31:5026-5032.
The authors conducted a prospective safety study of women who did or did not receive a pandemic H1N1 monovalent or trivalent influenza vaccine during pregnancy.  No clinically significant differences in the rate of spontaneous abortion, major birth defects, preterm delivery, or small for gestational age were detected.

Kharbanda EO, Vazquez-Benitez G, Lipkind H, Naleway A, Lee G, et al. Inactivated influenza vaccine during pregnancy and risks for adverse obstetric events. Obstet Gynecol 2013;122(3):659-667.
The authors compared the risks of adverse events during pregnancy in women who did or did not receive a trivalent inactivated influenza vaccine. More than 74,000 pregnant women were vaccinated during the 7-year-study period. Vaccine receipt did not confer an increased risk for adverse maternal outcomes such as hyperemesis, chronic hypertension, gestational hypertension, gestational diabetes, proteinuria, urinary tract infection, puerperal infections, venous complications, pulmonary emboli, peripartum cardiomyopathy, preeclampsia or eclampsia.

Ludvigsson JF, Strom P, Lundholm C, Cnattingius S, Ekbom A, et al. Maternal vaccination against H1N1 influenza and offspring mortality: population based cohort study and sibling design. BMJ 2015;351:h5585.
In this Swedish prospective study, the authors investigated the mortality of more than 41,000 pregnancies in mothers who either did or did not receive the influenza A(H1N1)pdm09 vaccine. Mothers vaccinated during pregnancy were not at increased risk of adverse neonatal outcomes such as stillbirth, early neonatal death (first six days of life) or later death (7 days of life up to 4.6 years of age), regardless of the trimester during which they were vaccinated.

Fabiani M, Bella A, Rota M, Clagnan E, Gallo T, et al. A/H1N1 pandemic influenza vaccination: a retrospective evaluation of adverse maternal, fetal, and neonatal outcomes in a cohort of pregnant women in Italy. Vaccine 2015;33:2240-2247.
The authors evaluated the risk of adverse maternal, fetal, and neonatal outcomes in more than 2000 pregnant women in Italy vaccinated during the second or third trimester with the 2009 MF59-adjuvanted A/H1N1 pandemic influenza vaccine. They found no statistically significant association between vaccine receipt and maternal outcomes (i.e., hospital admissions for influenza, pneumonia, hypertension, eclampsia, diabetes, thyroid disease, and anemia), fetal outcomes (i.e, fetal death after the 22nd gestational week), and neonatal outcomes (i.e., preterm birth, low birth weight, low 5-minute Apgar score, and congenital malformations).

Zerbo O, Modaressi S, Chan B, Goddard K, Lewis N, et al. No association between influenza vaccination during pregnancy and adverse birth outcomes. Vaccine 2017;35:3186-3190.
The authors evaluated the association between maternal influenza vaccination during pregnancy and risk of preterm birth, small or large for gestational age, admission to the neonatal intensive care unit, need for mechanical ventilation, respiratory distress syndrome, low birth weight, and low Apgar scores during a 6-year period in more than 145,000 women among whom 64,000 were vaccinated.  The authors found no association between maternal influenza vaccination during pregnancy and increased risk for adverse outcomes.

Kharbanda EO, Vazquez-Benitez G, Romitti PA, Naleway AL, Cheetham TC, et al. First trimester influenza vaccination and risks of major structural birth defects in offspring.  J Pediatr 2017;187:234-239.
The authors examined the risks for major structural defects in infants following receipt of inactivated influenza vaccine in the first trimester during 10 influenza seasons. More than 50,000 mothers received inactivated influenza vaccine in the first trimester during the study period. The authors found no increased risk for cardiac, orofacial, respiratory, neurologic, ophthalmologic, otologic, gastrointestinal, genitourinary and muscular or limb defects in the offspring of women who were vaccinated during the first trimester.

Hviid A, Svanstrom H, Molgaard-Nielsen D, Lambach P. Association between pandemic influenza A(H1N1) vaccination in pregnancy and early childhood morbidity in offspring. JAMA Pediatr 2017;171(3):239-248.
The authors evaluated whether administration of pandemic influenza A(H1N1) vaccination during pregnancy increased the risk for early childhood morbidity. They found that children whose mothers received influenza vaccine during pregnancy were not more likely to be hospitalized in early childhood than those whose mothers weren’t vaccinated, regardless of trimester exposure.

Pertussis vaccine

Fortner KB, Swamy GK, Broder KR, Jimenez-Truque N, Zhu Y, et al. Reactogenicity and immunogenicity of tetanus toxoid, reduced diphtheria toxoid, and acellular pertussis vaccine (Tdap) in pregnant and nonpregnant women. Vaccine 2018;36:6354-6360.
In this prospective, observational, cohort study, the authors investigated the reactogenicity and immunogenicity following Tdap vaccination. Moderate or severe reactions were not significantly higher in pregnant compared with non-pregnant women. 

Sukumaran L, McCarthy NL, Kharbanda EO, Vazquez-Benitez G, Lipkind HS, et al. Infant hospitalizations and mortality after maternal vaccination. Pediatrics 2018;141(3):e20173310.
The authors evaluated whether maternal receipt of influenza and Tdap vaccines increased the risk of infant hospitalization or death in the first six months of life during a 10-year period. They found no association between vaccination and infant all-cause hospitalization, hospitalization from respiratory causes, or mortality.  

DeSilva M, Vazquez-Benitez G, Nordin JD, Lipkind HS, Klein NP, et al. Maternal Tdap vaccination and risk of infant morbidity. Vaccine 2017;35:3655-3660. 
A slight increase in the risk of chorioamnionitis in women vaccinated with Tdap during pregnancy was previously detected in two previous Vaccine Safety Datalink (VSD) evaluations. In this study, the authors investigated the clinical significance of these findings by reviewing four years of data from seven VSD sites, including more than 45,000 women vaccinated during pregnancy. An increased risk of chorioamnionitis was observed in women vaccinated during pregnancy compared to those who were not vaccinated. Despite these findings, no increased risk of clinically significant outcomes typically associated with chorioamnionitis was found in infants born to Tdap-vaccinated women, including transient tachypnea of the newborn, neonatal sepsis, neonatal pneumonia, respiratory distress syndrome or newborn convulsions. 

Layton JB, Butler Am, Li D, Boggess KA, Weber DJ, et al. Prenatal Tdap immunization and risk of maternal and newborn adverse events. Vaccine 2017;35:4072-4078.
The authors evaluated the relationship between Tdap vaccination during pregnancy and adverse birth outcomes in more than 148,000 women during a five-year period. Vaccination during pregnancy was not associated with an increased risk of preeclampsia, eclampsia, cesarean section or placental abruption compared to unvaccinated women.

DeSilva M, Vazquez-Benitez G, Nordin JD, Lipkind HS, Romitti PA, et al. Tdap vaccination during pregnancy and microcephaly and other structural birth defects in offspring. JAMA 2016;316(17):1823-1824.
Using the Vaccine Safety DataLink, the authors compared the prevalence of birth defects between infants born to more than 41,000 pregnant women who received Tdap vaccine with unvaccinated women. Vaccination at less than 14 weeks gestation, between 27- and 36-week gestation, or at any time during pregnancy was not associated with an increased risk for microcephaly or any structural defect. 

Hoang, HTT, Leuridan E, Maertens, K, et al. Pertussis vaccination during pregnancy in Vietnam: results of a randomized controlled trial. Vaccine 2016;34:151-159.
In this randomized controlled trial, the authors assessed the safety and efficacy of the pertussis vaccine in pregnant women in Vietnam. Both Tdap and tetanus toxoid vaccines were well tolerated.

Kharbanda EO, Vazquez-Benitez G, Lipkind HS, Klein NP, Cheetham TC, et al. Maternal Tdap vaccination: coverage and acute safety outcomes in the Vaccine Safety Datalink, 2007-2013. Vaccine 2016;34;968-973.
The authors evaluated the risks for adverse events following Tdap vaccination in more than 53,000 pregnant women. They found no increased risk of acute adverse events within 3- or 42-days post-vaccination, including neurologic events, thrombotic events, new onset proteinuria, gestational diabetes, cardiac events, venous thromboembolic events or thrombocytopenia.

Maertens K, Cabore RN, Huygen K, Hens N, Van Damme P, et al. Pertussis vaccination during pregnancy in Belgium: results of a prospective controlled cohort study. Vaccine 2016;34:142-150.
In this prospective, controlled cohort study, the authors assessed the immunogenicity and safety of Tdap immunization during pregnancy. Tdap was generally well-tolerated with mild side effects resolving within 72 hours of vaccine receipt. No reported serious adverse events in the mothers were related to vaccine administration. All reported serious adverse events in infants were common conditions that occur in the neonatal/infant period and were not linked to maternal vaccination.

Petousis-Harris H, Walls T, Watson D, Paynter J, Graham P, et al. Safety of Tdap vaccine in pregnant women: an observational study. BMJ Open 2016;6:e010911.
In this prospective study, the authors followed 800 New Zealand women who received Tdap during the third trimester of pregnancy. Immunization was well-tolerated with no serious adverse events occurring at levels greater than background rates. 

Morgan JL, Baggari SR, McIntire DD, Sheffield JS. Pregnancy outcomes after antepartum tetanus, diphtheria and acellular pertussis vaccination Obstet Gynecol 2015;125(6):1433-1438.
The authors retrospectively evaluated pregnancy outcomes in more than 7,100 women who had or had not received Tdap during pregnancy during a 13-month period. They found no differences in pregnancy outcomes (e.g., stillbirth, major malformations, chorioamnionitis, 5-minute Apgar score, or cord blood pH) or neonatal complications (e.g., ventilation requirement, sepsis, intraventricular hemorrhage, or neonatal death). Additionally, no differences in neonatal outcomes were found between women who had received at least two Tdap vaccines in the past five years with those who had received only a single dose.  

Sukumaran L, McCarthy NL, Kharbanda EO, Weintraub E, Vazquez-Benitez G, et al. Safety of tetanus, diphtheria, and acellular pertussis and influenza vaccinations in pregnancy. Obstet Gynecol 2015;126(5):1069-1074.
The authors evaluated the safety of Tdap and influenza vaccines in 36,000 pregnancies during a seven-year period. Concomitant administration of Tdap and influenza vaccines during pregnancy was not associated with a higher risk of acute adverse outcomes (e.g., fever, limb pain, limb swelling, cellulitis, lymphadenitis, Arthus reaction, or allergy) or birth outcomes (e.g., preterm delivery, low birth weight, small for gestational age) compared to sequential vaccination. No cases of Arthus reaction or Guillain-Barre Syndrome were reported.  

Sukumaran L, McCarthy NL, Kharbanda EO, McNeil MM, Naleway AL, et al. Association of Tdap vaccination with adverse birth outcomes among pregnant women with prior tetanus-containing immunizations. JAMA 2015;314(15):1581-1587. 
The authors evaluated the safety of Tdap vaccine in more than 29,000 pregnant women. They found no statistically significant differences in acute adverse events (e.g., fever, allergic reactions or local reactions) or adverse birth outcomes (e.g., preterm delivery, low birth weight, small for gestational age) among women who had received their prior tetanus-containing vaccine less than two years before and two to five years before compared with women who had received a tetanus containing vaccine more than five years earlier. No cases of anaphylaxis, Arthus reaction or Guillain-Barre Syndrome were found following vaccination. 

Donegan K, King B, Byran P. Safety of pertussis vaccination in pregnant women in UK: observational study. BMJ 2014;349:g4219.
The authors conducted an observational cohort study to examine the safety of pertussis vaccination during pregnancy following administration of Repevax®, a low-dose diphtheria, acellular pertussis and inactivated poliomyelitis vaccine. When compared with national historical rates, the authors found no increased risk of stillbirth, maternal or neonatal death, pre-eclampsia, eclampsia, hemorrhage, fetal distress, uterine rupture, placenta or vasa previa, caesarean delivery, low birth weight, or neonatal renal failure. 

Kharbanda EO, Vazquez-Benitez G, Lipkind HS, Klein NP, Cheetham TC, et al. Evaluation of the association of maternal pertussis vaccination with obstetric events and birth outcomes. JAMA 2014;312(18):1897-1904.  
Using the Vaccine Safety Datalink, the authors determined the safety of Tdap vaccination during pregnancy. Vaccination was not associated with increased risks of adverse birth outcomes including preterm delivery, small for gestational age, or hypertensive disorders of pregnancy (e.g., gestational hypertension, preeclampsia, eclampsia, etc.). Although Tdap vaccination during pregnancy was initially associated with a slightly increased risk of chorioamnionitis, chart reviews found that the association between Tdap vaccination at 27- and 36-week gestation was no longer significant.   

Munoz FM, Bond NH, Maccato M, Pinell P, Hammill HA, et al. Safety and immunogenicity of tetanus diphtheria and acellular pertussis (Tdap) immunization during pregnancy in mothers and infants. JAMA 2014;311(17):1760-1769.
In this randomized, double-blind, placebo-controlled clinical trial, the authors evaluated the safety and immunogenicity of Tdap immunization during the third trimester of pregnancy. No Tdap-associated serious adverse events occurred in women or infants. There were no significant differences in the infants’ gestational ages, birth weights, Apgar scores, neonatal examinations, growth, development or complications when comparing those mothers who received Tdap antepartum versus postpartum.

Prematurity and vaccines

Acellular pertussis vaccine and prematurity

Schloesser RL, Fischer D, Otto W, Rettwitz-Volk W, Herden P, et al. Safety and immunogenicity of an acellular pertussis vaccine in premature infants. Pediatrics 1999;103(5):e60.
The authors prospectively evaluated the safety and immunogenicity of an acellular pertussis vaccine in preterm infants compared with full-term infants at 2 months of age, followed by two additional doses at four and eight weeks after the initial dose. Immune responses to the acellular pertussis vaccine were decreased in preterm compared with term infants, but vaccine efficacy was high. Acellular pertussis vaccine was well tolerated in both groups and the incidence of systemic adverse reactions was limited to one patient in each group having a fever > 38.5C.

Concomitant or combination vaccine receipt and prematurity

Omenaca F, Vazquez L, Garcia-Corbeira P, Mesaros N, Hanssens L, et al. Immunization of preterm infants with GSK’s hexavalent combined diphtheria-tetanus-acellular pertussis-hepatitis B virus-inactivated poliovirus and Haemophilus influenzae type b conjugate vaccine: a review of safety and immunogenicity. Vaccine 2018;36:986-996.
The authors reviewed 10 clinical studies and 15 years of post-marketing safety surveillance data regarding immunization with hexavalent vaccine (DTaP/HepB/IPV/Hib) when administered alone or in combination with pneumococcal conjugate, rotavirus, and meningococcal vaccines and respiratory syncytial virus IgG to infants with a history of prematurity or low birthweight (LBW). At least 92% of infants with a history of LBW or as young as 24 weeks gestational age responded to all vaccine antigens after the three-dose vaccination series. Between 13% and 30% of medically stable infants with a history of prematurity or LBW developed apnea after vaccination, typically after the first dose. The occurrence of post-immunization cardiorespiratory events was influenced by the severity of underlying neonatal conditions, though most events resolved spontaneously or required minimal intervention.  The hexavalent vaccine was well tolerated in co-administration regimens.

Montague EC, Hilinski JA, Williams HO, McCracken CE, Giannopoulos HT, et al. Respiratory decompensation and immunization of preterm infants. Pediatrics 2016;137(5):e20154225.
The authors retrospectively evaluated the safety of routine infant vaccinations (DTaP, IPV, HepB, Hib, PCV, and rotavirus) and influenza vaccine to 240 premature infants born at less than 32 weeks of gestation who were immunized during their hospital stay over a 6.5-year period. Fewer than 10% of infants required increased respiratory support within 72 hours of vaccination. Two percent (2%) of infants required reintubation, all of whom had bronchopulmonary dysplasia (BPD) and a birthweight of less than 650 grams (1 pound 6 ounces). An increased incidence of apnea/bradycardia/desaturation events was observed in infants with and without BPD, but no differences existed between groups.  Most infants received three or more vaccines per day, though the number of vaccines administered in a day was not associated with an increase of adverse events after immunization. The authors concluded that respiratory decompensation requiring clinical intervention after immunization of preterm infants both with and without BPD was uncommon and immunization should not be delayed.

DeMeo SD, Raman SR, Hornik CP, Wilson CC, Clark R, et al. Adverse events after routine immunization of extremely low-birth-weight infants. JAMA Pediatr 2015;169(8):740-745.
The authors retrospectively evaluated the incidence of adverse events after vaccination between the ages of 53 and 100 days in more than 13,000 infants born at 28 weeks of gestation or less and birthweight ≤ 1000 grams. More than 90% of infants received three or more vaccines. Infants who were born at 23 to 24 weeks gestation had a higher risk of sepsis evaluation and intubation after immunization. No increase in the incidence of seizures was detected. The post-immunization incidence of adverse events was similar across immunization types, including combination vaccines when compared with single-dose vaccines. 

Faldella G, Galleti S, Corvaglia L, Ancora G, Alessandroni R. Safety of DTaP-IPV-Hib-HBV hexavalent vaccine in very premature infants. Vaccine 2007;25:1036-1042.
In this prospective, observational study, the safety of DTaP-IPV-Hib-HBV hexavalent vaccine was evaluated in 45 preterm newborns less than 31 weeks of gestation admitted to the NICU who received the vaccine between day of life 49 and 112. Vaccination was generally well tolerated, with 11% showing either a transient recurrence of or increase in apnea and bradycardia episodes following immunization, but intervention was limited to tactile stimulation, supplemental oxygen or bag and mask ventilation, and no patients were intubated. All patients with cardiorespiratory events had chronic diseases. The authors also specifically evaluated cardiac disturbances (QTc interval) and cerebral blood flow effects but found no differences in these parameters before and after vaccination or in those infants who experienced cardiorespiratory events.

Lee J, Robinson JL, Spady DW. Frequency of apnea, bradycardia, and desaturations following first diphtheria-tetanus-pertussis-inactivated polio-Haemophilus influenzae type B immunization in hospitalized preterm infants. BMC Pediatr 2006;6:20.
In this retrospective study, the authors investigated the frequency of apnea, bradycardia and desaturations in approximately 250 hospitalized very preterm infants (mean gestational age 26 weeks) to determine if incidences of these events were increased following the first dose of DTP/DTaP-IPV-Hib vaccine. A significant increase in the incidence of cardiorespiratory events was detected after vaccine administration compared with unvaccinated infants, though most events were clinically insignificant and the need for intervention was not different between the groups.

Schulzke S, Heininger U, Lucking-Famira M, Fahnenstich H. Apnea and bradycardia in preterm infants following immunisation with pentavalent or hexavalent vaccines. Eur J Pediatr 2005;164:432-435. 
In this retrospective study, the authors investigated the incidence of apnea and bradycardia in respiratory-stable preterm infants (mean gestational age 28 weeks and postnatal age ~ 2 months) following a combination DTaP/Hib/IPV or DTaP/Hib/IPV/HepB. Vaccination was generally well tolerated, with 13% showing either a transient recurrence of or increase in apnea and bradycardia episodes following immunization, but intervention was limited to tactile stimulation, supplemental oxygen or bag and mask ventilation, and no patients were intubated.

DTaP vaccine and prematurity

Carbone T, McEntire B, Kissin D, Kelly D, Steinschneider A, et al. Absence of an increase in cardiorespiratory events after diphtheria-tetanus-acellular pertussis immunization in preterm infants: a randomized, multicenter study. Pediatrics 2008;121(5):e1085-e1090.
In this randomized, controlled, prospective study, the authors examined the relationship between DTaP and cardiorespiratory events in approximately 200 preterm infants (mean post-conception age of 35 weeks) at 2 months of age. Preterm infants who received DTaP at 2 months of age were not more likely to experience prolonged apnea and bradycardia in the 48-hour post-immunization period than infants who did not receive DTaP. 

Pfister RE, Aeschbach V, Niksic-Stuber V, Martin BC, Siegrist CA. Safety of DTaP-based combined immunization in very-low-birth-weight premature infants: frequent but mostly benign cardiorespiratory events. J Pediatr 2004;145:58-66. 
The authors evaluated the safety of DTaP-IPV-Hib immunization in very low birthweight preterm infants (mean gestational age 28 ± 2 weeks; range 24-34 weeks) when administered prior to hospital discharge during the first two to four months of life. Nearly half of the infants had a reappearance or increase in either apnea, bradycardia, or desaturations after vaccination, though all infants returned to baseline within 48-72 hours and most events resolved spontaneously or after brief stimulation. No event resulted in a detrimental impact on the infants’ clinical course, reintubation or a delay in discharge. The authors concluded that timely vaccine receipt in this fragile population is safe.

Hib vaccine and prematurity

Omenaca F, Garcia-Sicilia J, Carcia-Corbeira P, Boceta R, Romero A. Response of preterm newborns to immunization with a hexavalent diphtheria-tetanus-acellular pertussis-hepatitis B virus-inactivated polio and Haemophilus influenzae type b vaccine: first experiences and solutions to a serious and sensitive issue. Pediatrics 2005;116(6):1292-1298.
The authors prospectively evaluated the safety and immunogenicity of a hexavalent DTaP/HepB/IPV/Hib vaccine in approximately 200 preterm and full-term infants at 2, 4, and 6 months of age. Preterm and full-term infants displayed good immune responses to all antigens. Protective immune responses against Hib occurred in more than 90% of preterm infants, though these responses were less than those of term infants. An increased risk of oxygen desaturations or bradycardia was observed in preterm infants born < 28 weeks with birth weights less than or equal to 1000 grams in the 72 hours after their first dose of vaccine, and reintubation was not reported.

Pfister RE, Aeschbach V, Niksic-Stuber V, Martin BC, Siegrist CA. Safety of DTaP-based combined immunization in very-low-birth-weight premature infants: frequent but mostly benign cardiorespiratory events. J Pediatr 2004;145:58-66. 
The authors evaluated the safety of DTaP-IPV-Hib immunization in very low birthweight preterm infants (mean gestational age 28 ± 2 weeks; range 24-34 weeks) when administered prior to hospital discharge during the first two to four months of life. Nearly half of the infants had a reappearance or increase in either apnea, bradycardia, or desaturations after vaccination, though all infants with increased events returned to baseline within 48-72 hours and most of these events resolved spontaneously or after brief stimulation. No event resulted in a detrimental impact on the infants’ clinical course, reintubation or a delay in discharge. The authors concluded that timely vaccine receipt in this fragile population is safe.

Influenza vaccine and prematurity

Esposito S, Pugni L, Daleno C, Ronchi A, Valzano A, et al. Influenza A/H1N1 MF59-adjuvanted vaccine in preterm and term children aged 6 to 23 months. Pediatrics 2011;127(5):e1161-e1168.
In this prospective, randomized study, the immunogenicity, safety and tolerability of a monovalent 2009 pandemic influenza A/H1N1 MF59-adjuvanted vaccine was evaluated in approximately 100 children aged 6 to 23 months of age, including those born at less than 32 weeks of gestation. Regardless of gestational or postnatal age, all children developed protective immune responses after two doses, and all but one child was protected after the first dose. The vaccine was generally well tolerated, with fever recorded as the only adverse event; no differences were detected when comparing infants with differing gestational ages (< 32 weeks versus 32-36 weeks versus 37-42 weeks). Local reactions were minimal (less than 4% occurrence) and did not differ between gestational age groups, indicating the tolerability of the MF59 adjuvant. No severe adverse events occurred in any patient.

Measles vaccine and prematurity

McClure D, Jacobsen SJ, Klein NP, Naleway AL, Kharbanda EO, et al. Similar relative risks of seizures following measles containing vaccination in children born preterm compared to full-term without previous seizures or seizure-related disorders. Vaccine 2019;37(1):76-79.
The authors retrospectively evaluated the incidence of febrile seizures following measles vaccine at age 12 through 23 months over a 13-year period in more than 530,000 children to determine if the risk is affected by prematurity. The overall incidence of febrile seizures was low and no differences were found in the risk of febrile seizure between children born preterm versus full term. 

Pneumococcal vaccine and prematurity

Martinón-Torres F, Czajka H, Center KJ, Wysocki J, Majda-Stanislawska E, et al. 13-valent pneumococcal conjugate vaccine (PCV13) in preterm versus term infants. Pediatrics 2015;135(4):e876-e886.
In this prospective study, the authors compared the safety and efficacy of PCV13 age when administered with other routine vaccines (e.g., DTaP, hepatitis B, IPV, Hib, meningococcal group C conjugate vaccine) in term and preterm infants. Immune responses to PCV13 were lower in preterm infants, though the majority of subjects in both groups achieved protective antibody levels. PCV13 was well tolerated in both term and preterm infants, with the most common problem being irritability or decreased sleep in the preterm group.

Esposito S, Pugni L, Bosis S, Proto A, Cesati L, et al. Immunogenicity, safety and tolerability of heptavalent pneumococcal conjugate vaccine administered at 3, 5, and 11 months post-natally to pre- and full-term infants. Vaccine 2005;23:1703-1708.

In this prospective study, the authors assessed the immunogenicity, safety and tolerability of PCV7 administered at 3, 5 and 11 months of age in preterm and full-term infants. PCV7 was immunogenic in both groups when given as a three-dose series. PCV7 was generally well tolerated with irritability and drowsiness occurring regardless of gestational age.

Shinefield H, Black S, Ray P, Fireman B, Schwalbe J, et al. Efficacy, immunogenicity and safety of heptavalent pneumococcal conjugate vaccine in low birth weight and preterm infants. Pediatr Infect Dis J 2002;21:182-186.
In this randomized, double bind trial, more than 37,000 infants were given either PCV7 or meningococcal serogroup C conjugate vaccine (MCV), including approximately 6,000 low birth weight or preterm infants. The vaccine was efficacious in 100% of infants. PCV7 was well tolerated by all infants, regardless of gestational age or birthweight. An increased incidence of hives was found in the low birthweight and preterm groups who received PCV compared with those who received MCV. Preterm infants receiving PCV also had an increased risk of vomiting, irritability, loss of appetite, and diarrhea compared with those receiving MCV.

Rotavirus vaccine and prematurity

Omenaca F, Sarlangue J, Szenborn L, Nogueira M, Suryakiran PV, et al. Safety, reactogenicity and immunogenicity of the human rotavirus vaccine in preterm European infants: a randomized phase IIIB study. Pediatr Infect Dis J 2012;31(5):487-493.
In this randomized, placebo-controlled trial, the safety and efficacy of rotavirus vaccine (Rotarix^®) was evaluated in approximately 1,000 preterm infants (mean gestational age 33 weeks). Immunologic responses to the vaccine were comparable to full-term infants evaluated in previous studies. No differences in the incidence of serious adverse events were detected when comparing vaccine and placebo recipients, with the most common reported finding being fever (less than 5%). Gastroenteritis episodes were also similar between vaccine and placebo recipients. No intussusception cases were reported. 

Goveia MG, Rodriguez ZM, Dallas MJ, Itzler RF, Boslego JW, et al. Safety and efficacy of the pentavalent human-bovine (WC3) reassortant rotavirus vaccine in healthy premature infants. Pediatr Infect Dis J 2007;26(12):1099-1104.
In this randomized, placebo-controlled trial, the safety and efficacy of rotavirus vaccine (Rotateq^®) was evaluated in approximately 70,000 healthy infants 6-12 weeks of age, including more than 2,000 born prematurely. Rotavirus vaccine was well tolerated among preterm infants, including those born at less than 32 weeks of gestation. No differences in the incidence of serious adverse events were detected between preterm vaccine and placebo recipients. No cases of intussusception in any premature infant were found during the study. These results support vaccinating healthy premature infants on the same schedule as term infants.