Spectrum of disease due to Haemophilus influenzae type b occurring in vaccinated children

Haemophilus b polysaccharide vaccine was first licensed in the United States in April 1985. Between May 1985 and September 1987, 228 reports of disease due to Haemophilus influenzae in vaccinated children were submitted to the Food and Drug Administration, of which 216 were accepted for analysis. We compared the relative frequencies of the different disease entities caused by H. influenzae type b reported in vaccinated children with those reported in unvaccinated children (greater than 1000 cases that occurred between 1973 and 1984, as reported in the literature). Over 90% of the vaccinated children were greater than or equal to 24 mo of age. A higher proportion of cases was reported to have occurred within the first two months after vaccination, with 10 cases occurring within 72 h of vaccination. Vaccination did not alter the expected frequencies of the different clinical entities associated with invasive H. influenzae disease. No estimates of clinical efficacy are possible based on the adverse events submitted to the Food and Drug Administration.