A new multinational study offers encouraging evidence that COVID-19 vaccination during pregnancy, particularly with a booster dose, significantly reduces the risk of preeclampsia, a serious and potentially life-threatening complication of pregnancy. The research, published in eClinicalMedicine, analyzed data from over 6,500 pregnant women across 18 countries.
Preeclampsia affects an estimated 3–8% of pregnancies worldwide and is a leading cause of maternal and neonatal morbidity and mortality. Its exact cause remains unknown, but inflammation and vascular dysfunction are known contributing factors – mechanisms that also play a role in COVID-19 infection. The study provides “unprecedented insight into preeclampsia prevention, independent of the direct effects of COVID-19 infection,” according to researchers involved in the INTERCOVID Consortium.
Study Details and Key Findings
The study, formally titled “COVID-19 vaccination status during pregnancy and risk of preeclampsia: the pandemic-era cohort of the INTERCOVID Consortium,” recruited participants between 2020 and 2022. Researchers compared vaccinated and unvaccinated women, both those who contracted SARS-CoV-2 and those who did not, to determine the impact of vaccination status on preeclampsia rates.
The data revealed a concerning link between COVID-19 infection during pregnancy and increased preeclampsia risk. Infection was associated with a 45% increase in risk, rising to 78% among unvaccinated pregnant women. However, vaccination demonstrated a protective effect. Vaccination reduced the overall odds of preeclampsia by 33% among women who received a booster dose – a statistically significant finding.
The benefits of vaccination were particularly pronounced for women with pre-existing health conditions such as diabetes, hypertension, or thyroid disorders. In this group, vaccination with a booster dose cut the risk of preeclampsia by 42%, also statistically significant. This suggests that vaccination may be especially important for individuals already at higher risk of developing preeclampsia.
Importantly, the protective effect of vaccination persisted even after adjusting for key confounding factors. This suggests that the benefits extend beyond simply preventing COVID-19 infection and may relate to a broader immunological or vascular benefit. Vaccinated women also experienced lower rates of preterm delivery, maternal and perinatal morbidity, and mortality.
Further analysis showed that among women who received a booster dose, there was a 33% reduction in the risk of preterm delivery, a 32% reduction in maternal and perinatal morbidity, and a 29% reduction in severe adverse perinatal outcomes – all statistically significant.
Understanding the Potential Mechanisms
“We offer evidence from the first large study suggesting that COVID vaccination may protect against one of the most serious pregnancy complications,” said Dr. Jagjit S. Teji, a neonatologist at Ann & Robert H. Lurie Children’s Hospital of Chicago and clinical assistant professor of pediatrics at Northwestern University Feinberg School of Medicine, a co-author of the study.
Researchers hypothesize that vaccination may modulate the immunological and vascular pathways involved in the development of preeclampsia. This aligns with growing evidence suggesting that some vaccines can have “non-specific” beneficial effects on immune regulation. The study supports the idea that vaccination can positively influence these pathways, potentially offering protection even in the absence of COVID-19 infection.
Global Implications and Recommendations
“This is the first large-scale prospective evidence demonstrating that COVID-19 vaccination, particularly with booster doses, can help prevent preeclampsia,” noted Professor Paolo Ivo Cavoretto of the IRCCS San Raffaele Hospital in Milan, Italy. “It is important to highlight that this protective effect is greater among women with underlying diseases, who are at the highest risk.”
The findings underscore the importance of strengthening existing vaccination programs for pregnant women, with a particular emphasis on booster dose coverage and equitable access worldwide. Spanish research centers, including the IIS Aragón and the Hospital Clínico Universitario Lozano Blesa in Zaragoza, along with Hospital Vall d’Hebron in Barcelona, were among the 41 centers across 18 countries that participated in this crucial research.
Professor José Villar, co-lead author of the study and principal investigator of the INTERCOVID Consortium at the University of Oxford (UK), emphasized that these results go beyond the already known benefits of COVID-19 vaccination during pregnancy. “Now we have evidence that maternal vaccination can influence the pathways involved in the development of preeclampsia, suggesting a broader immunological or vascular benefit of vaccination.”
While these findings are promising, it’s important to remember that this research represents a significant step forward in understanding preeclampsia prevention. Continued research is needed to further elucidate the mechanisms involved and to optimize vaccination strategies for pregnant women globally.
