Vaccine effectiveness for preventing COVID-19 hospital admission during pregnancy: a population-based cohort study in England during the Alpha and Delta waves of the SARS-CoV-2 pandemic

This research has not been peer-reviewed. It is a preliminary report that should not be regarded as conclusive, guide clinical practice or health-related behaviour, or be reported in news media as established information.


To 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.


Population-based cohort study using national, linked Census and administrative data.


England, United Kingdom, from 8th December 2020 to 31st August 2021.


815,4777 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 measures 

A 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.


Compared 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.


COVID-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.

Author list



  1. Office for National Statistics, Health Analysis and Life Events, Newport, NP10 8XG, UK
  2. Leicester Real World Evidence Unit, Diabetes Research Centre, University of Leicester, UK
  3. Population Data Science, Swansea University Medical School, Faculty of Medicine, Health & Life Science, Swansea University, UK
  4. National Perinatal Epidemiology Unit, Nuffield Department of Population Health, University of Oxford, UK
  5. Public Health Scotland, Edinburgh, EH12 9EB, UK
  6. Usher Institute, University of Edinburgh, Edinburgh, EH16, 4UX
  7. UCL Great Ormond Street Institute of Child Health, London, UK
  8. Health Data Science Centre, Fondazione Human Technopole, Milan, Italy 
  9. MRC Integrative Epidemiology Unit, University of Bristol, Bristol, UK


Matthew L. Bosworth1, Ryan Schofield1, Daniel Ayoubkhani1,2, Loes Charlton1, Vahé Nafilyan1, Kamlesh Khunti2, Francesco Zaccardi2, Clare Gillies2, Ashley Akbari3, Marian Knight4, Rachael Wood5,6, Pia Hardelid7, Luisa Zuccolo8,9, Camille Harrison1

Novel Coronavirus SARS-CoV-2