['To identify a possible effect of pertussis vaccination in infancy on the risk for developing human IDDM.', 'A comparison was made of the cumulative incidence of IDDM in children age 0-12 years between two birth cohorts born before pertussis vaccination and two birth cohorts born after pertussis vaccination had been excluded from the Swedish national immunization program. The Swedish Childhood Diabetes registry was used to identify cases of IDDM. Yearly nurse reports on administered vaccines were used to determine coverage for diphtheria/tetanus/pertussis (DTP) and diphtheria/tetanus (DT) vaccines. Pertussis vaccine coverage was estimated based on number of doses of vaccine made available on license.', 'No difference in cumulative incidence rate of IDDM up to the age of 12 years was found when the birth cohorts for 1978 and 1979 with high DTP vaccination coverage were compared with the cohorts of 1980 and 1981 with low pertussis vaccination coverage.'] Is cumulative incidence of childhood-onset IDDM unaffected by pertussis immunization?