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 retarded. Other diseases caused by Hib include:
Hib is a bacterium that is commonly found lining the surface of the nose and the back of the throat. Many children will come in contact with Hib sometime in the first two years of life. 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 would get serious and occasionally fatal infections with Hib. Most children harmed by Hib were previously healthy and well nourished.
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 the 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 2012, fewer than 25 cases of Hib in children 5 years of age and younger were reported to the Centers for Disease Control and Prevention (CDC).
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 have serious side effects.
Although the Hib vaccine prevents what was once the most common cause of bacterial meningitis, it does not prevent all causes of meningitis. Other causes of bacterial meningitis include pneumococcus (see pneumococcus vaccine) and meningococcus (see meningococcus vaccine). The pneumococcal vaccine was recommended for all infants in 2000. The meningococcal vaccine was recommended for all adolescents in 2005. Some viruses also cause meningitis; however, viral meningitis is often less severe than that caused by bacteria.
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. Unfortunately, because of vaccine safety concerns, some parents have refused the Hib vaccine for their children, and in 2009, four children died as a result.
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||Vaccine Risks|
Plotkin SA, Orenstein W, and Offit PA. Haemophilus influenzae vaccines in Vaccines, 6th Edition. 2012, 167-182.
Reviewed by: Paul A. Offit, MD
Date: April 2013
Materials in this section are updated as new information becomes available. The Vaccine Education Center staff regularly reviews materials for accuracy.
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