Safety of vaccination against influenza A (H1N1) during pregnancy in the Netherlands: results on pregnancy outcomes and infant's health: cross-sectional linkage study.

ObjectiveThis study aims to assess the safety of Influenza A(H1N1), vaccination administered during the second and third trimester and containing MF59 and thiomersal (Focetria((R))), measured by pregnancy outcomes and infant's health. DesignCross-sectional linkage study. Setting and sampleA sample of pregnant women, eligible for prenatal screening, were invited to participate. MethodsQuestionnaire data were linked with the Netherlands Perinatal Registry (n=1920). Information on infant growth, development (n=1739) and infection-related contacts with the general practitioner (GP) during the first year of life (n=1671) was obtained. Main outcome measuresMultivariate logistic regression was used to assess the association between H1N1 vaccination and small-for-gestational-age infant, preterm delivery and a composite adverse outcome, i.e. low Apgar-score, neonatal intensive care unit admission, neonatal resuscitation or perinatal death. Influence of maternal vaccination on growth, development and GP infection-related contact rates were assessed using multivariate linear mixed modelling and multivariate negative binomial regression, respectively. ResultsResponse rate was 21%. Though we found differences in characteristics between unvaccinated and vaccinated women, in the multivariate analyses no association was found between H1N1 vaccination and small-for-gestational-age (odds ratio [OR] 0.84; 95% confidence interval [95% CI] 0.50-1.43), preterm delivery (OR 0.98; 95% CI 0.59-1.62) and the composite adverse outcome (OR 0.84; 95% CI 0.44-1.60). We found no differences in weight-for-age (-0.05; 95% CI -0.13 to 0.04), length-for-age (-0.01; 95% CI -0.09 to 0.06), head-circumference-for-age (-0.05; 95% CI -0.13 to 0.03), developmental scores (-0.06; 95% CI -0.28 to 0.17) and infection-related GP contact rates (incidence rate ratio 1.07; 95% CI 0.91-1.28) between infants of unvaccinated and vaccinated mothers. ConclusionPregnancy outcomes did not differ between H1N1-vaccinated and unvaccinated women. Furthermore, growth, development and GP infection-related contact rates, assessed after the first year of life, were similar in offspring of vaccinated and unvaccinated mothers.