Questions & Answers

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What causes Hib disease?
Hib disease is caused by a bacterium, Haemophilus influenzae. There are six different types of these bacteria (a through f). Type b organisms account for 95% of all strains that cause invasive disease, and this is the type against which the Hib vaccine protects.

How does Hib disease spread?
Hib disease is spread person-to-person by direct contact or through respiratory droplets. Usually the organisms remains in the nose and throat, but occasionally the bacteria spread to the lungs or bloodstream and cause a serious infection in the individual.

How long does it take to show signs of Hib disease after being exposed?
The incubation period of Hib disease is not certain, but could be as short as a few days.

What are the symptoms of Hib disease?
A person with invasive Hib disease can have different symptoms depending on what body systems are affected. (See next question.)

How serious is Hib disease?
Hib disease can be very serious. The most common type of invasive Hib disease is meningitis, an infection of the membranes covering the brain (50%-65% of cases). Symptoms of Hib meningitis are fever, decreased mental status, and stiff neck. The mortality rate is 2%-5%. In addition, 15%-30% of survivors suffer some permanent neurologic damage, including blindness, deafness, and mental retardation.

Another 17% of invasive Hib cases include epiglottitis, an infection and swelling in the throat that can cause life-threatening airway blockage. Other forms of invasive Hib disease include: joint infection (8%), skin infection (6%), pneumonia (15%), and bone infection (2%).

How do I know if my child has Hib disease?
The diagnosis of Hib disease is usually made based on one or more laboratory tests using a sample of infected body fluid, such as blood or spinal fluid.

Is there a treatment for Hib disease?
Hib disease is treated with antibiotics for 10 days. Most cases require hospitalization.

Even with antibiotic treatment, up to 5% of all children with Hib meningitis die from the disease.

How common is Hib disease in the United States?
Before the introduction of a Hib vaccine, H. influenzae type b (Hib) was the leading cause of bacterial meningitis among children younger than age five years in the United States. Every year about 20,000 children younger than age five years got severe Hib disease and about 1,000 individuals died. More than half of children who developed severe Hib disease were younger than age 12 months.

Since 1988, when a Hib vaccine was first introduced, the incidence of Hib disease has decreased more than 99%. From 1996 through 2000, an average of 68 children per year were reported with Hib disease. Most recent cases have occurred in unvaccinated or incompletely vaccinated children.

Can you get Hib disease more than once?
Yes. A child with Hib disease may not develop protective levels of antibodies. Children younger than age 24 months who have recovered from invasive Hib disease should be considered unprotected and receive the Hib vaccine as soon as possible.

Questions and answers about hib vaccine

Technically reviewed by the Centers for Disease Control and Prevention, April 2007