This week, WAidid suggest an article on Quadrivalent HPV Vaccination and the Risk of Adverse Pregnancy Outcomes, recently published on NEJM.
Human papillomavirus (HPV) vaccines are recommended for all girls and women from 9 to 26 years of age. Although HPV vaccination is not recommended in pregnancy, a number of women will be inadvertently vaccinated early in the first trimester of unplanned or unrecognized pregnancies. However, data on the safety of vaccination during pregnancy are limited. The clinical trials of HPV vaccines did not include women who were known to be pregnant. Consequently, analyses of safety during pregnancy were based on data from clinical trials focused mainly on the risk of adverse pregnancy outcomes associated with HPV vaccines that were administered before pregnancy onset, observational studies, and data based on voluntary reporting.
To assess the safety of HPV vaccine further, the authors conducted a nationwide register-based cohort study involving all pregnant women in Denmark, investigating the association between quadrivalent HPV vaccination during pregnancy and the risks of a major birth defect, spontaneous abortion, stillbirth, preterm birth, low birth weight, and small size for gestational age. Using the Medical Birth Register and the National Patient Register, they identified all pregnancies in Denmark that ended in a singleton birth or an abortive outcome, between October 1, 2006 and November 30, 2013. During the study period, the quadrivalent HPV vaccine (Gardasil, Sanofi Pasteur MSD) was the sole HPV vaccine used in the Danish national vaccination program.
The authors identified 581,550 eligible pregnancy: five unmatched subcohorts were created, according to the outcomes specific exposure windows and exclusion criteria. Before matching was performed, the authors found that vaccinated women were younger, more often nulliparous, had lower levels of education, were more likely to be in the two lowest quintiles of household income, more likely to be unmarried, and more likely to be smokers than were unvaccinated women.
Quadrivalent HPV vaccination during pregnancy was not associated with significantly greater risks of adverse pregnancy outcomes. It was not associated with a significantly higher risk of spontaneous abortion, small size for gestational age, stillbirth, major birth defect, preterm birth, and low birth weight.
The authors concluded that their results are consistent with other evidence that does not indicate that the vaccination of pregnant women with inactivated virus, bacterial, or toxoid vaccines generally confers a higher risk of adverse pregnancy outcomes than no such vaccination. They highlighted the strength of their large population-based cohort analysis, but also the limitations related to the evaluation of recoded data and the absence of a statistical power to assess some rare pregnancy outcomes (the risks of stillbirth and specific major birth defects).
AUTHORS: Nikolai M. Scheller, Björn Pasternak, Ditte Mølgaard-Nielsen, Henrik Svanström and Anders Hviid
Click here to go to the article.