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 remain 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 include 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 results in epiglottitis, an infection and swelling in the throat that can lead to life-threatening airway blockage. Other forms of invasive Hib disease include joint infection (8%), skin infection (6%), pneumonia (15%), and bone infection (2%).

Two tragic incidents showing the seriousness of Hib were reported from both Minnesota and Pennsylvania in early 2009. Minnesota reported a total of five cases of invasive Hib disease in children younger than 5 years from 2008, the largest number since 1992. Three of the children had not been vaccinated because of parent/guardian deferral or refusal. One of these children died. In Pennsylvania, seven cases were reported for the six-month period from October 2008 - March 2009. Only one child had received any vaccine (1 dose) and 3 of the children died.

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, usually for 10 days. Most cases require hospitalization. Even with antibiotic treatment, 3%-6% 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 children died. More than half of children who developed severe Hib disease were younger than age 12 months.

From 1996 through 2000, an average of 68 reported cases of Hib disease occurred in children younger than age 5 years each year. By 2008, this number had dropped to just 30 cases and, although some of the 163 cases with unknown serotype could have been due to Hib, the significant decline in incidence (>99%) since the pre-vaccine era is truly remarkable.

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.