Older pediatricians understand the value of the Haemophilus influenzae type b vaccine. They watched this vaccine, first introduced in the early 1990s, virtually eliminate a disease that affected about 20,000 children every year in the United States. Three to four doses of this vaccine are recommended for all children between 2 and 15 months of age.

The disease

What is Haemophilus influenzae type b?

Haemophilus influenzae type b (Hib) is a bacterium that infects the lining of the brain, causing meningitis. Meningitis is caused by several different bacteria. However, before the Hib vaccine, Hib was by far the most common cause of meningitis. Children with meningitis often have fever, stiff neck and drowsiness. Symptoms can progress to include coma and death. Some children recover from the disease but are left permanently paralyzed, deaf, blind or mentally impaired. Hib can also cause bloodstream infection (sepsis), pneumonia, cellulitis, arthritis and epiglottitis. Perhaps no disease was more frightening than this last one. The epiglottis, a tissue that sits on top of the windpipe, prevents food from entering the windpipe when swallowing. When the epiglottis is infected, it blocks the windpipe, causing suffocation and occasionally death.

Find out more about meningitis in this video discussion between two CHOP doctors.

How do you catch Hib?

Hib is a bacterium that is commonly found lining the surface of the nose and the back of the throat. Because most adults have immunity to Hib, a mother will passively transfer antibodies from her own blood to the blood of her newborn baby before the baby is born. The antibodies that the baby gets before birth usually last for a few months. However, after that time, the baby is unprotected. Most children who first come in contact with Hib don't have a problem. But before the Hib vaccine, about 20,000 children every year in the United States would get serious and occasionally fatal infections with Hib. Most children harmed by Hib were previously healthy and well nourished.

The vaccine

How is the Hib vaccine made?

The Hib vaccine is made from the sugar coating (polysaccharide) of the bacteria. Antibodies directed against the Hib polysaccharide protect the child against an infection that could result in permanent disabilities or death.

Unfortunately, children less than 2 years old don't develop very good immune responses to this polysaccharide, even if exposed to it through infection. For this reason, children less than 2 years old who catch Hib and survive the infection are still recommended to receive Hib vaccine.

Scientists have figured out that by taking the Hib polysaccharide and linking it to a harmless protein, young children are able to make a stronger immune response to the polysaccharide. This “conjugated” version of the Hib vaccine works extremely well. Before the vaccine, Hib caused about 20,000 cases of serious disease in the United States every year. In 2016, 30 cases of Hib in children 5 years of age and younger were reported to the Centers for Disease Control and Prevention (CDC).

What are the side effects of the Hib vaccine?

After receiving the Hib vaccine, some children may feel pain or soreness in the local area of the shot and occasionally get a low-grade fever. The Hib vaccine does not cause serious side effects.

Other questions you might have

Is this vaccine recommended for anyone other than infants?

Most often this vaccine is given to infants. But, in a few cases other people may be recommended to get this vaccine, such as those:

• Without a spleen or preparing to having their spleen surgically removed
• With sickle cell disease
• Who had a bone marrow transplant
• Between 5 and 18 years old who have been diagnosed with HIV

If you are concerned that you or a family member might need this vaccine, talk with your healthcare provider.

Is it true that more than one type of infection can cause meningitis?

Yes. Everyone has heard it on the news—the story of a local student infected with meningitis. Such a report inevitably results in many questions and a great amount of concern and even fear among families with children in the affected school.

There are some important considerations when this happens. First, it is important to remember that meningitis refers to an infection that has reached the lining of the brain and spinal cord. Second, it can be caused by viruses or bacteria (hence the terms viral meningitis or bacterial meningitis). 

Viral meningitis, the most common type of meningitis, is often less severe than bacterial meningitis. Vaccine-preventable diseases that can cause viral meningitis include measles, mumps, chickenpox and influenza.

Most, but not all, cases of bacterial meningitis can be prevented by vaccination. The bacteria most often associated with meningitis include meningococcus, pneumococcus, and Haemophilus influenzae type B (often referred to as Hib). Fortunately, by the age of 2, most children are fully immunized against pneumococcus and Hib, and most adolescents are protected against meningococcus.

Other diseases caused by Hib include:

• Sepsis (bloodstream infection)
• Epiglottitis (severe swelling of the epiglottis, a tissue that closes off the windpipe during swallowing)
• Arthritis (infection of the joints)
• Pneumonia (infection of the lungs)
• Cellulitis (most commonly involving the side of the cheek, called buccal cellulitis)

Relative risks and benefits

Do the benefits of the Hib vaccine outweigh its risks?

The Hib vaccine has caused a dramatic decline in the incidence of meningitis, bloodstream infections, and pneumonia caused by Hib. However, Hib bacteria still circulate in the community and occasionally cause disease. 

On the other hand, the Hib vaccine causes no serious side effects. Therefore, the benefits of the Hib vaccine clearly outweigh its risks.

Disease risks

• Meningitis (fever, stiff neck, drowsiness; in a small number of cases coma)
• Sepsis (bloodstream infection)
• Epiglottitis (severe swelling of the epiglottis, a tissue that closes off the windpipe during swallowing)
• Arthritis (infection of the joints)
• Cellulitis (a skin infection)
• Pneumonia (infection of the lungs)
• Disease can be fatal

Vaccine risks

• Pain or soreness at the injection site
• Low-grade fever

Reference

Plotkin SA, Orenstein W, Offit PA, and Edwards KM. Haemophilus influenzae vaccines in Vaccines, 7th Edition. 2018, 301-318.