COVID-19 vaccination reduces the risk of preeclampsia among pregnant women who have received a booster dose by 33%, a 2026 prospective cohort study has found.
COVID-19 infection during pregnancy was associated with a 45% increased risk of preeclampsia during the pandemic, increasing to 78% among unvaccinated women.
Preeclampsia and COVID-19
Preeclampsia is a leading cause of maternal and neonatal morbidity and mortality. It consistently overlaps with COVID-19 in terms of major risk factors: inflammation and vascular dysfunction and both known contributors.
COVID-19 Vaccination and Preeclampsia Rates
The study analysed data from more than 6,500 pregnant women across 40 hospitals and 18 countries, enrolled between 2020 and 2022.
Preeclampsia rates were monitored across vaccinated and unvaccinated cohorts, and across women with and without SARS-CoV-2 infection.
Amid the overall 33% protective effect, vaccination with a booster also reduced preeclampsia risk by 58% for women with pre-existing morbidities including diabetes, hypertension, or thyroid disorders.
Protective effects were stronger in women diagnosed with COVID-19.
Preterm Delivery, Morbidity, and Mortality
Vaccinated women also experienced lower odds of preterm delivery, maternal and perinatal morbidity, and mortality.
Women with a booster dose has a 33% lower chance of preterm birth, 32% reduced risk of maternal morbidity and mortality, and 29% lower odds of perinatal morbidity.
Baseline Characteristics
Women vaccinated with a booster dose were generally taller, more educated, more likely to be married or cohabiting, and worked less outside the home. They had fewer non-SARS-CoV-2 infections and took more multivitamins and aspirin, both of which are protective factors for preeclampsia.
They were also older, smoked less, drank more, had lower parity, and took fewer calcium supplements. All could affect preeclampsia risk.
Researchers warned of a risk of selection bias related to vaccination uptake, possible residual confounding variables, and the risk of overstating results without statistical significance.
Preeclampsia Aetiology
Findings established that the benefits of COVID-19 vaccination status during pregnancy extend beyond the severity of infection, leading to a reduction of preeclampsia, preterm birth, maternal and perinatal morbidity, and mortality.
Researchers emphasised the importance of a coordinated programme designed to better understand preeclampsia aetiology, and how the immune system interacts with infections and vaccination.
Reference
Cavoretto PI et al. COVID-19 vaccination status during pregnancy and preeclampsia risk: the pandemic-era cohort of the INTERCOVID consortium. EClinicalMedicine. 2026;DOI:10.1016/j.eclinm.2026.103785.
