Pertussis vaccination and wheezing illnesses in young children: prospective cohort study

Objectives To examine the relation between pertussis vaccination and the pr evalence of wheezing illnesses in young children. Design Prospective cohort study. Setting Three former health districts comprising Avon Health Authority. Subjects 9444 of 14 138 children enrolled in the Avon longitudinal study of pregnancy and childhood and for whom data on wheezing symptoms, vaccinatio n status, and 15 environmental and biological variables were available. Main outcome measures Episodes of wheezing from birth to 6 months, 7-18 mon ths, 19-30 months, and 31-42 months. These time periods were used to derive five categories of wheezing illness: early wheezing (not after 18 months); late onset wheezing (after 18 months); persistent wheezing (at every time period); recurrent wheezing (any combination of two or more episodes for ea ch period); and intermittent wheezing (any combination of single episodes o f reported wheezing). These categories were stratified according to parenta l self reported asthma or allergy. Results Unadjusted comparisons of the defined wheezing illnesses in vaccina ted and non-vaccinated children showed no significant association between p ertussis vaccination and any of the wheezing outcomes regardless of stratif ication for parental asthma or allergy. Wheeze was more common in non-vacci nated children at 18 months, and there was a tendency for late onset wheezi ng to be associated with non-vaccination in children whose parents did not have asthma, but this was not significant. After adjustment for environment al and biological variables, logistic regression analyses showed no signifi cant increased relative risk for any of the wheezing outcomes in vaccinated children: early wheezing (0.99, 95% confidence interval 0.80 to 1.23), lat e onset wheezing (0.85, 0.69 to 1.05), persistent wheezing (0.91, 0.41 to 1 .79), recurrent wheezing (0.96, 0.72 to 1.26), and intermittent wheezing (1 .06, 0.81 to 1.37). Conclusions No evidence was found that pertussis vaccination increases the risk of wheezing illnesses in young children. Further follow up of this pop ulation with objective measurement of allergy and bronchial responsiveness is planned to confirm these observations.