Vaccine Eliminates a Major Cause of Intellectual Disability
The development of a vaccine for Hib is one of the NICHD's greatest contributions to public health.
Hib is a commonly occurring bacterial infection. In the 1970s, this often-fatal infection was the leading cause of meningitis (inflammation of the brain) among children younger than age 5 in the United States. Even with effective antibiotic treatment, 5% of the 20,000 children who contracted Hib each year died, and about 30% were left with intellectual disability (then called mental retardation), deafness, or seizures. In fact, Hib meningitis was the leading cause of acquired intellectual disability in the nation at the time.
Vaccine research at the time focused on using whole bacteria that had been killed, or of weakened bacteria, that could sometimes cause severe side effects. Two researchers in the NICHD intramural research program—Dr. John B. Robbins and Dr. Rachel Schneerson—took a different tack in their research. Their research focused on the polysaccharide (sugar) molecule on the surface of the bacteria. Using polysaccharides eliminated many of the severe side effects of killed-bacteria vaccines, while still producing ample amounts of antibody (molecules made by the immune system) in adults and older children to prevent disease. Scientists supported by the National Institute of Allergy and Infectious Diseases did further vaccine testing. With the added involvement of industry, three Hib-purified polysaccharide vaccines were produced and licensed in 1985.
But those vaccines failed to stimulate protective antibody levels in infants, the age group with the highest incidence of serious disease. In fact, many scientists believed it was impossible to develop a vaccine for infants that relied on polysaccharides because immature defenses of the infant immune system were not savvy enough to detect the polysaccharide and make antibodies.
Dr. Robbins and Dr. Schneerson continued their efforts, developing a new conjugate technology to create a vaccine. They linked the weak polysaccharide to a protein that was easily recognized by the immature immune system of infants. The resulting conjugate vaccine was soon found to be effective in infants, as well as in older children.
Hib conjugate vaccines have been licensed since 1987 and have become part of the routine pediatric immunization series given to infants starting at age 2 months. The development of the vaccine has reduced Hib infection by more than 99% in the United States, to fewer than 100 cases in 2002, saving countless lives and preventing a once-leading cause of intellectual disability. With widespread use of the vaccine, it may be possible to end this disease throughout the world.