Association of Inadvertent 9-Valent Human Papillomavirus Vaccine in Pregnancy With Spontaneous Abortion and Adverse Birth Outcomes.

Importance: The 9-valent human papillomavirus (9vHPV) vaccine is recommended for individuals through age 26 years and may be administered to women up to age 45 years. Data on 9vHPV vaccine exposures during pregnancy are limited. Objective: To evaluate the associations between 9vHPV vaccine exposures during pregnancy or peripregnancy and selected pregnancy and birth outcomes (spontaneous abortion [SAB], preterm birth, small-for-gestational age [SGA] birth, and major structural birth defect). Design, Setting, and Participants: This cohort study analyzed data from 7 participating health systems in the Vaccine Safety Datalink. The cohort comprised pregnancies among girls and women aged 12 to 28 years that ended between October 26, 2015, and November 15, 2018. Singleton pregnancies that ended in a live birth, stillbirth, or SAB were included. Exposures: Vaccine exposure windows were distal (9vHPV or 4vHPV vaccine administered from 22 to 16 weeks before last menstrual period [LMP]), peripregnancy (9vHPV vaccine administered from 42 days before LMP until LMP), and during pregnancy (9vHPV vaccine administered from LMP to 19 completed weeks' gestation). Primary comparisons were (1) girls and women with 9vHPV vaccine exposures during pregnancy vs those with 4vHPV or 9vHPV distal vaccine exposures, (2) girls and women with vaccine exposures peripregnancy vs those with 4vHPV or 9vHPV distal vaccine exposures, and (3) girls and women with 9vHPV vaccine exposures during pregnancy or peripregnancy vs those with 4vHPV or 9vHPV distal vaccine exposure. Main Outcomes and Measures: Spontaneous abortions were confirmed based on medical record review and adjudication. Preterm and SGA births were identified from electronic health record and birth data. Major structural birth defects were based on diagnostic codes using a validated algorithm. Inverse probability weighting was used to balance the covariates. Time-dependent covariate Cox proportional hazards regression models and Poisson regression were used to estimate the associations between 9vHPV vaccine exposures and pregnancy and birth outcomes. Results: The final cohort included 1493 pregnancies among girls and women with a mean (SD) maternal age of 23.9 (2.9) years. Of these pregnancies, 445 (29.8%) had exposures to the 9vHPV vaccine during pregnancy, 496 (33.2%) had exposures to the 9vHPV vaccine peripregnancy, and 552 (37.0%) had 4vHPV or 9vHPV distal vaccine exposures. The 9vHPV vaccine administered during pregnancy was not associated with increased risk for SAB (hazard ratio, 1.12; 95% CI, 0.66-1.93) compared with distal vaccine exposures. Findings were similar for 9vHPV vaccine exposures peripregnancy (relative risk [RR], 0.72; 95% CI, 0.42-1.24). Among live births (n = 1409), 9vHPV vaccine exposures during pregnancy were not associated with increased risks for preterm birth (RR, 0.73; 95% CI, 0.44-1.20) or SGA birth (RR, 1.31; 95% CI, 0.78-2.20). Results were similar regarding the association between 9vHPV vaccine exposures peripregnancy and preterm birth (RR, 0.72; 95% CI, 0.45-1.17) and SGA birth (RR, 1.10; 95% CI, 0.65-1.88). Birth defects were rare in all exposure groups, occurring in about 1% of live births with available infant data. Conclusions and Relevance: This study found that 9vHPV vaccine exposures during or around the time of pregnancy were uncommon and not associated with SABs or selected adverse birth outcomes. These findings can inform counseling for inadvertent 9vHPV vaccine exposures.