HPV vaccine exposure during pregnancy not linked to adverse outcomes
medwireNews: Women who inadvertently receive the quadrivalent human papillomavirus (HPV) vaccine during pregnancy are not at increased risk for adverse pregnancy outcomes over women with no such exposure, results of a Danish nationwide cohort study show.
Using data from 581,550 pregnancies recorded in the Danish national register between 2006 and 2013, Nikolai Scheller and colleagues, from Statens Serum Institut in Copenhagen, created five outcome-specific subcohorts to assess whether HPV vaccination during pregnancy was associated with an increased risk for adverse outcomes.
Each subcohort contained between 463 and 1774 women who received their vaccination during a prespecified time window based on the outcome being assessed; for example, the first trimester for the analysis of major birth defects. These women were then matched to unvaccinated women in a 1:4 ratio based on age, year of pregnancy, and propensity score.
Regression analyses showed that exposure to the quadrivalent HPV vaccine during pregnancy was not associated with a significantly increased risk for major birth defect, spontaneous abortion, preterm birth, low birth weight, small size for gestational age, or stillbirth, when compared with no exposure.
Writing in The New England Journal of Medicine, Scheller and co-authors say: “Our 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.”
In an accompanying editorial, Kathryn Edwards, from Vanderbilt University School of Medicine in Nashville, Tennessee, USA, writes: “These data are very encouraging and strongly support the safety of HPV vaccines if they are inadvertently given in pregnancy, a finding that complements previous safety reports of HPV vaccine in nonpregnant women.”
She adds: “These data also show that adverse outcomes occur at a baseline rate in pregnancy and that when no control group is included in studies, these outcomes may be inappropriately attributed to the vaccine.”
Edwards also comments that postmarketing safety evaluations of vaccines not meant for, but unintentionally given to, pregnant women are of “great importance.”
She concludes: “The carefully conducted postlicensure safety study of HPV vaccine now reported in [The New England Journal of Medicine] is a model for others to emulate.”
By Laura Cowen
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