Dr. Frank Destefano, of the Centers for Disease Control and Prevention, in Atlanta, Georgia, and colleagues with the Vaccine Safety Datalink research group, examined the association between childhood vaccinations and the risk of asthma. They conducted a cohort study including 167,240 children who were followed from birth to at least 18 months of age and up to a maximum of 6 years of age.

Overall, 18,407 children (11%) developed asthma, according to the team. The median age at onset was 11 months. They observed no associations between diphtheria, tetanus and whole cell pertussis vaccine (relative risk 0.92), oral polio vaccine (RR 1.09), and measles, mumps, and rubella vaccine (RR 0.97) and the risk of developing asthma in infancy or childhood.

The relative risk associated with the Haemophilus influenza type B (Hib) and hepatitis B vaccines were 1.18 and 1.20, respectively. The team notes, however, that the Hib result was not consistent across health maintenance organizations.

Furthermore, "In a subanalysis restricted to children who had at least two medical care encounters during their first year, the relative risks decreased to 1.07 for Hib and 1.09 for hepatitis B vaccine," Dr. Destefano and colleagues explain.

They conclude that this weak association is at least partially attributable to medical care utilization bias.

Pediatr Infect Dis J 2002;21:498-504.