[Trial of prevention of severe Haemophilus influenzae type b infections and trial of tolerance, after PRP-T vaccination, in the Val-de-Marne region].

BACKGROUND:Protein-polysaccharide conjugate H influenzae vaccine is now routinely recommended for infants. To assess the vaccine's protective efficacy against invasive H influenzae infections and its safety, we conducted a study in the Val-de-Marne area of France. METHODS:From April 1991 to April 1993, 22,443 children less than 5 years of age were given PRP-T vaccine. Infants less than 6 months were given three doses whereas those between 6 and 12 months received only two doses, and children over 1 year of age received one dose. According to the infant's DTP-IPV vaccination status, PRP-T was administered alone or reconstituted extemporaneously with DTP-IPV. The immunogenicity of the conjugate vaccine was assessed after three doses in 100 infants under the age of 6 months. RESULTS:The PRP-T vaccine administered alone was safe. The reactions were more frequent when PRP-T vaccine was combined with DTP-IPV vaccine but they were comparable in frequency and severity to those observed after DTP-IPV vaccination. Before 1992, 18 Hib infections were reported each year in the Val-de-Marne region. During the study, only three Hib infections were reported each year. CONCLUSIONS:The fall in incidence of Hib infections, greater than expected, suggests a widespread immune effect of the vaccine, possibly due to a decrease in Hib nasopharyngeal carriage. The antibody titres to each component of vaccine were comparable to those observed in previous clinical infant studies.