Has Human Papillomavirus (HPV) Vaccination Prevented Adverse Pregnancy Outcomes? Population-Level Analysis After 8 Years of a National HPV Vaccination Program in Australia

Background. Human papillomavirus (HPV) infection, and its sequelae of precancerous cervical lesions and their subsequent treatment, have been linked with an increased risk of adverse pregnancy outcomes. Publicly funded HPV vaccination of female adolescents began in Australia in 2007 with initial catch-up to age 26 years. Methods. Using data from the National Perinatal Data Collection we compared rates of preterm births and small-for-gestational-age infants born in Australia 2000-2015. We used generalized linear models, assuming a Poisson distribution and log link function, with single-year categories of infant birth year, maternal age, and age-specific HPV vaccination coverage as independent variables. Results. In maternal cohorts with 60%-80% HPV vaccination coverage as achieved in Australia, there was a relative rate reduction of 3.2% (95% confidence interval, 1.1%-5.3%) in preterm births and 9.8% (8.2% to 11.4%) in small-for-gestational-age infants, after adjustment for infant's birth year and maternal age. Conclusion. This analysis provides provisional population-level evidence of a reduction in adverse pregnancy outcomes in cohorts of women offered HPV vaccination. Confounding by smoking or other variables and/or ecological analysis limitations, however, cannot be excluded. These findings indicate potential broader benefits of HPV vaccination than have been documented to date.