Causal relation is likely

EDITOR—We initiated and funded a collaborative study with Tuomilehto on the effect of the Haemophilus influenzae type b vaccine on type 1 diabetes and found that the data support a causal relation (paper submitted for publication). Furthermore, the potential risk of the vaccine exceeds the potential benefit. We compared a group that received four doses of the vaccine, a group that received one dose, and a group that was not vaccinated. The cumulative incidence of diabetes per 100 000 in the three groups receiving four, one, and no doses of the vaccine was 261, 237 and 207 at age 7 and 398, 376 and 340 at age 10 respectively.

Karvonen et al's analysis is not rational, and their conclusion is not supported by our data.1 Their calculations of relative risk are also misleadingly low, and we urge readers to check them. Most researchers would compare the group who received four doses with the group that was not vaccinated or the two vaccinated groups with the group that was not vaccinated. The results of both comparisons reach significance. The …