The protective efficacy of Haemophilus b polysaccharide vaccine
E. D. Shapiro, T. V. Murphy, E. R. Wald and C. A. Brady
Department of Pediatrics, Yale School of Medicine, New Haven, CT 06510-8064.
To assess the protective efficacy of the Haemophilus b polysaccharide
vaccine, a case-control study was conducted in Connecticut, Dallas County,
and greater Pittsburgh. Seventy-six children 24 to 72 months of age who had
H influenzae type b isolated from normally sterile sites from August 1985
through July 1987 were enrolled. For each case two controls, matched by age
and place of residence, were randomly selected from the records of all live
births in the area. Antecedent receipt of the Haemophilus b polysaccharide
vaccine was ascertained from the records of all physicians and clinics at
which the subjects received medical care. Overall, 12% of the cases and 39%
of the controls had received the vaccine. The estimate of the protective
efficacy of the vaccine was 88% overall (95% confidence interval, 74% to
96%) and 91% (95% confidence interval, 71% to 99%), 92% (95% confidence
interval, 76% to 99%), and 81% (95% confidence interval, 45% to 96%) in
Connecticut, Dallas County, and greater Pittsburgh, respectively. The
estimates were not substantially affected by adjusting with logistic
regression for differences between the cases and controls in race and the
attendance of group day care. We conclude that the Haemophilus b
polysaccharide vaccine is highly effective in these areas among children
who receive the vaccine when they are 24 months of age or older.
