November 27, 1998
Contact: CDC, Division of Media Relations
(404) 639-3286

The United States has nearly erased a disease that, until recently, was the most common cause of bacterial meningitis among pre-school children. According to a report in this week's CDC Morbidity and Mortality Weekly Report (MMWR), since 1988, Haemophilus influenzae type b, or Hib, invasive disease has decreased 99 percent among U.S. children following widespread vaccination against Hib.

Despite this dramatic decline, Hib continues to circulate and U.S. children who do not receive their primary vaccination series on time or are too young to be vaccinated are at risk of Hib invasive disease that can cause bacterial meningitis. Invasive Hib disease occurs when the bacteria spreads in the bloodstream to various sites in the body, especially the lining of the brain. In 1997, 258 cases of Hib invasive disease were reported to CDC. In the early 1980s, before Hib vaccine was available, approximately 20,000 cases of Hib invasive disease occurred in children under age 5; of those, 12,000 cases were meningitis.

"This is a true public health victory accomplished in a very short span of years. Before Hib vaccine became widely available, 1 in 200 pre-school children developed serious complications caused by Hib. Today, we're close to totally controlling Hib disease in the United States. Vaccines are extremely important to the health of our nation's children," said CDC Director Jeffrey P. Koplan, M.D., M.P.H. "Hib vaccine should be valued as a way to prevent a deadly disease that less than a generation ago plagued our youngest children. Parents should ask at every medical visit whether their child needs a vaccination."

Invasive disease can affect many of the body's organ systems, especially infecting the membranes covering the brain, called meningitis. Symptoms of Hib meningitis are fever, decreased mental awareness and a stiff neck. Up to 5 percent of children who develop invasive Hib disease will die and from 15 to 30 percent of those with meningitis will suffer mental retardation or deafness.

Humans are the only known reservoir for the Hib bacterium, which is spread primarily through respiratory droplets. Hib does not survive in the environment and on household surfaces. However, close contact with a child suffering from Hib such as in a day-care setting can lead to additional cases of the disease among playmates.

"Despite this incredible decline in cases, the threat from Hib continues. Health-care providers should emphasize to parents the importance of vaccinating their children against Hib invasive disease at the recommended ages," said Walter A. Orenstein, M.D., director of CDC's National Immunization Program. "In the United States today, no child should be left vulnerable to this disease when safe and effective vaccines are available."

Up to 60 percent of invasive Hib disease occurs in children before they reach 12 months of age. Children vaccinated with the Hib vaccine are much less likely to carry the bacteria, decreasing the chance that younger, unvaccinated children will be exposed. After 5 years of age, few children develop Hib invasive disease.

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