Haemophilus b Polysaccharide Vaccine-Reply

In Reply. —  We congratulate Coles et al on the innovative use of discharge diagnosis data, and we agree with the conclusion that the polysaccharide Haemophilus vaccine provided protective efficacy in children aged 24 to 59 months. A randomized trial of the vaccine in Finland¹ as well as three postlicensure case-control studies^2-4 all demonstrated a protective effect of the vaccine. Only one study,⁵ a small case-control study with wide confidence limits, suggested a lack of efficacy.Although surveillance data can provide important supporting evidence of efficacy, there are methodological difficulties in using surveillance data to estimate the efficacy of a vaccine, as can be seen in the data presented by Coles et al. Year-to-year variation during the period of 1980 to 1984, when no vaccine was available, was substantial for the two younger age groups, 0 to 23 and 24 to 59 months of age. In fact,