The study, published in eClinicalMedicine, titled “COVID-19 Vaccination Status During Pregnancy and Preeclampsia Risk: The Pandemic-Era Cohort of the INTERCOVID Consortium”, analysed data from 6,527 pregnant women across 18 countries enrolled between 2020 and 2022. Researchers compared vaccinated and unvaccinated women, with and without SARS-CoV-2 infection, to assess how vaccination status influenced preeclampsia rates.
Key Findings
- COVID-19 infection during pregnancy was associated with a 45% increased risk of preeclampsia, which rose to 78% among unvaccinated women.
- Vaccination reduced the overall odds of preeclampsia amongst women receiving a booster dose by 33%, statistically significant.
- Among women with pre-existing health conditions such as diabetes, hypertension, or thyroid disorders, vaccination with a booster cut preeclampsia risk by 58%, statistically significant.
- The protective effect of vaccination remained consistent after adjusting for key factors and may be extended beyond COVID-19 infection, suggesting potential benefits for preeclampsia prevention regardless of infection status.
- Vaccinated women also experienced lower odds of preterm delivery, maternal and perinatal morbidity, and mortality.
- In addition, amongst women that have a booster dose, the protective effect for preterm birth was 33%, maternal morbidity and mortality was 32%, severe perinatal morbidity and mortality was 29%, all of them statistically significant.
Senior co-author
“These results go beyond the known benefits of COVID-19 vaccination in pregnancy. We now have evidence that maternal vaccination may influence pathways involved in preeclampsia development, suggesting a broader immunological or vascular benefit of vaccination.”
Professor José Villar, the senior co-author of the study and Principal Investigator of the INTERCOVID consortium from the Nuffield Department of Women’s & Reproductive Health, University of Oxford (UK)
Understanding Preeclampsia and its causes
Preeclampsia affects up to 3 to 8% of pregnancies worldwide, depending on the risk profile, and is a leading cause of maternal and neonatal morbidity and mortality. The origins of preeclampsia are unknown and treatments and preventive measures must be improved, but inflammation, and vascular dysfunction are known contributors, mechanisms that overlap with COVID-19 infection.
The INTERCOVID findings support the idea that vaccination may modulate immune and vascular pathways involved in preeclampsia, potentially offering protection even in the absence of COVID-19 infection. This aligns with growing evidence that some vaccines may have beneficial “non-specific” effects on immune regulation.
Global Implications
“This is the first large-scale, prospective evidence showing that COVID-19 vaccination, particularly with boosters, may help prevent preeclampsia. Importantly, this protective effect is greatest among women with underlying health conditions who are at the highest risk."
Prof. Paolo Ivo Cavoretto, IRCCS San Raffaele Hospital, Milan (Italy).
These results support the importance to strengthen vaccination programs for pregnant women already in place, emphasising booster coverage and equitable access worldwide.
Funding and Collaboration
The original INTERCOVID study was supported by the University of Oxford’s COVID-19 Research Response Fund. The consortium includes over 40 hospitals across 18 countries, reflecting a truly global effort to understand maternal and perinatal outcomes during the pandemic.
Full publication
COVID-19 Vaccination Status During Pregnancy and Preeclampsia Risk: The Pandemic-Era Cohort of the INTERCOVID Consortium