RESUMEN

ObjectiveTo estimate vaccine effectiveness (VE) for preventing COVID-19 hospital admission in women first infected with SARS-CoV-2 during pregnancy, and assess how this compares to VE among women of reproductive age who were not pregnant when first infected. DesignPopulation-based cohort study using national, linked Census and administrative data. SettingEngland, United Kingdom, from 8th December 2020 to 31st August 2021. Participants815,4777 women aged 18 to 45 years (mean age, 30.4 years) who had documented evidence of a first SARS-CoV-2 infection in NHS Test and Trace data or Hospital Episode Statistics. Main outcome measuresA hospital inpatient episode where COVID-19 was recorded as the primary diagnosis. Cox proportional hazards models, adjusted for calendar time of infection and sociodemographic factors related to vaccine uptake and risk of severe COVID-19, were used to estimate VE as the complement of the hazard ratio for COVID-19 hospital admission. ResultsCompared with unvaccinated pregnant women, the adjusted rate of COVID-19 hospital admission was 76% (95% confidence interval 69% to 82%) lower for single-vaccinated pregnant women and 83% (75% to 88%) lower for double-vaccinated pregnant women. These estimates were similar to those found for non-pregnant women: 79% (76% to 81%) for single-vaccinated and 82% (80% to 83%) for double-vaccinated. Among those vaccinated more than 90 days before infection, being double-vaccinated was associated with a greater reduction in risk than being single-vaccinated. ConclusionsCOVID-19 vaccination is associated with reduced rates of severe illness in pregnant women infected with SARS-CoV-2, and the reduction in risk is similar to that for non-pregnant women. Waning of vaccine effectiveness occurs more quickly after one dose of a vaccine than two doses. What is already known on this topicBeing pregnant is a risk factor for severe illness and mortality following infection with SARS-CoV-2. Existing evidence suggests that COVID-19 vaccines are effective for preventing severe outcomes in pregnant women. However, research directly comparing vaccine effectiveness between pregnant and non-pregnant women of reproductive age at the population level are lacking. What this study addsOur study provides real-world evidence that COVID-19 vaccination reduces the risk of hospital admission by a similar amount for both women infected with SARS-CoV-2 during pregnancy and women who were not pregnant when infected, during the Alpha and Delta dominant periods in England.