Purpose of the Study
The development of allergy has been linked to a variety of factors, including genetic predisposition, environment, smoke exposure, and infection. Pertussis is known to act as an adjuvant to the development of sensitization in laboratory animal models. This observation was the background for this study, the purpose of which was to determine if pertussis vaccination was associated with allergen sensitization and the development of allergic disease in children.
The 669 children participating were part of the larger Swedish vaccine trial. This study was a randomized, double-blinded comparison of the effects of the 2-component acellular pertussis vaccine, the 5-component acellular pertussis vaccine, whole-cell pertussis vaccine, and DT vaccine used as a placebo.
The children were followed from 2 months until 2½ years of age. They were evaluated initially 1 month after the third immunization and again at 2½ years. Questions were asked of the caretakers regarding smoke, dampness, pets, feeding history, and allergic symptoms of the skin, nose, or lower airway. Skin testing to milk, egg white, and cat was done at the 7-month visit. At 2½ years the children were again tested to egg, cat, dog, dust mite, timothy grass, and birch tree pollen. Diagnostic criteria were set for asthma, atopic dermatitis, allergic rhinitis, and urticaria.
Allergic disease developed in 201 of the 699 children (28.8%). Atopic dermatitis occurred in 140 (21%), asthma in 67 (10%), allergic rhinitis in 14 (2%), urticaria in 15 (2%), and food allergy in 12 (2%). One or more positive skin tests occurred in 91 (14%) at 7 months and 63 (9%) at 2½ years. The cumulative incidence of atopic disease at age 2½ as well as individual manifestations of allergy were similar in the three pertussis vaccination groups and the DT group. The cumulative incidence of positive skin prick tests at both ages did not differ significantly between the groups. There were no differences in the prevalence of smoke, dampness, pets, preterm births, or gender in all four groups. There were 47 children who developed pertussis—25 in the DT group. The occurrence of pertussis was associated with an increased cumulative incidence of bronchial asthma (19% vs 9% in uninfected children).
This study showed that the incidence and manifestations of allergy during the first 2½ years of life was not increased after pertussis vaccination.
There has always been a concern that pertussis vaccines may augment the occurrence of allergy. While previous studies using smaller numbers of children have suggested an association, this larger study has shown that the pertussis vaccine did not cause an increase in allergy. This study is a solid contribution to the issue of allergy development and should help in counseling parents regarding preventative health care measures.