Allergic disease at the age of 7 years after pertussis vaccination in infancy: results from the follow-up of a randomized controlled trial of 3 vaccines.
OBJECTIVE
To prospectively assess sensitization rates and the development of allergic diseases in a follow-up of a randomized controlled pertussis vaccine trial.


SETTING
Two-month-old infants were the subject of this double-blind study in 1992 in a collaboration between the Pediatric Clinic and the Primary Care Centers in Linköping.


PATIENTS AND INTERVENTION
Allergic diseases were evaluated in 667 children, who were randomized to 1 of 4 vaccine groups: a 2-component, a 5-component, or a whole cell pertussis vaccine (all of which were administered with the diphtheria and tetanus toxoids vaccine) and the diphtheria and tetanus toxoids vaccine alone. Allergy development was assessed by questionnaires (n = 667) and skin prick tests (n = 538) at the age of 7 years.


MAIN OUTCOME MEASURES
Allergic diseases and skin prick test results at the age of 7 years.


RESULTS
The cumulative incidence of allergic diseases was 34.9%, and was similar in the 4 groups (33.3%-37.3%, P =.89), even after adjusting for family history, sex, pets, dampness, environmental smoking at home, and other living conditions. Positive skin prick test results were more prevalent, however, after vaccination with the 2-component acellular vaccine (19.4%) than in the other 3 groups (11.1%-13.5%, adjusted for confounding factors, P =.01). Furthermore, allergic rhinoconjunctivitis was more common in children who were initially immunized with the 2-component pertussis vaccine and received a booster dose with an acellular vaccine compared with those who received no booster vaccination (relative risk, 3.6; 95% confidence interval, 1.1-12.0).


CONCLUSION
Pertussis vaccination in infancy with any of these vaccines was not associated with allergic manifestations at the age of 7 years, apart from a higher prevalence of positive skin prick test results after an experimental 2-component vaccine, which is no longer in use.