A new multinational study from the INTERCOVID Consortium, led by researchers from the University of Oxford, has found that COVID-19 vaccination during pregnancy, particularly when combined with a booster dose, significantly reduces the risk of preeclampsia, a serious and potentially life-threatening pregnancy complication. The findings offer unprecedented insight into preeclampsia prevention, independent of the direct effects of COVID-19 infection.
The study, published in eClinicalMedicine , 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 42%, 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.
'These results go beyond the known benefits of COVID-19 vaccination in pregnancy,' said Professor José Villar , the senior co-author of the study and Principal Investigator of the INTERCOVID consortium from Oxford's Nuffield Department of Women's & Reproductive Health . 'We now have evidence that maternal vaccination may influence pathways involved in preeclampsia development, suggesting a broader immunological or vascular benefit of vaccination.'
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,' said Professor Paolo Ivo Cavoretto of IRCCS San Raffaele Hospital, Milan (Italy). 'Importantly, this protective effect is greatest among women with underlying health conditions who are at the highest risk.'
The paper, ' COVID-19 Vaccination Status During Pregnancy and Preeclampsia Risk: The Pandemic-Era Cohort of the INTERCOVID Consortium ', is published in eClinicalMedicine .
