COVID-19 Vaccine During Pregnancy Lowers Preeclampsia & Premature Birth Risk

COVID-19 vaccination during pregnancy may offer a significant protective effect against preeclampsia, a serious and potentially life-threatening blood pressure disorder that can occur during and after pregnancy. A new multinational study, published in February 2026 in eClinicalMedicine, reveals that vaccination, particularly with a booster dose, is associated with a reduced risk of developing this condition.

Preeclampsia and COVID-19: A Complex Relationship

Preeclampsia is characterized by high blood pressure and signs of damage to other organ systems, most often the liver and kidneys. It typically develops after 20 weeks of gestation and can lead to severe complications for both mother and baby, including preterm birth, seizures, stroke, and even death. The causes of preeclampsia are not fully understood, but inflammation and problems with blood vessel function are believed to play a role.

Researchers have observed a link between COVID-19 infection and an increased risk of preeclampsia. The new study confirms this association, finding that COVID-19 infection during pregnancy increased the risk of preeclampsia by 45 percent. This risk was even higher – 78 percent – among pregnant women who were unvaccinated when infected.

Vaccination Offers Significant Protection

The study, led by researchers from the University of Oxford’s INTERCOVID Consortium, analyzed data from 6,527 pregnant women across 18 countries, enrolled between 2020 and 2022. The findings demonstrate a clear benefit to vaccination. A booster dose of a COVID-19 vaccine reduced the overall odds of preeclampsia by 33 percent, a statistically significant result.

The protective effect of vaccination was particularly pronounced among women with pre-existing health conditions, such as diabetes, hypertension, or thyroid disorders. In this group, a booster vaccination cut the risk of preeclampsia by 42 percent, also statistically significant. This suggests that vaccination may be especially important for pregnant women with underlying health vulnerabilities.

Beyond Preeclampsia: Broader Benefits of Vaccination

The benefits of COVID-19 vaccination during pregnancy extend beyond reducing the risk of preeclampsia. Vaccinated women in the study also experienced lower odds of preterm delivery, maternal and perinatal morbidity (illness), and mortality. Specifically, vaccinated women who received a booster vaccination had a 33 percent lower risk of premature birth and a 29 percent lower mortality rate.

Understanding the Mechanism

While the precise mechanisms underlying the protective effect of vaccination are still being investigated, researchers believe it may be related to the impact of vaccination on both blood vessels and inflammation. “We now have evidence that maternal vaccination may have an impact on the development of preeclampsia,” explained Professor José Villar from the University of Oxford. “This suggests a broader immunological or vascular cause for the benefits of vaccination.”

The study authors hypothesize that vaccination may help to regulate the immune system and improve blood vessel function, thereby reducing the risk of preeclampsia. This is particularly relevant given the known role of inflammation and vascular dysfunction in the development of the condition. The findings suggest that the benefits of vaccination may be independent of whether or not a woman contracts COVID-19, potentially offering a preventative effect even in the absence of infection.

Implications for Public Health

These findings reinforce current recommendations for COVID-19 vaccination during pregnancy. Health organizations continue to emphasize the safety and effectiveness of COVID-19 vaccines for pregnant women and those planning to become pregnant. The study provides further evidence to support these recommendations and highlights the potential for vaccination to improve maternal and infant health outcomes.

The research also opens avenues for further investigation into the underlying mechanisms linking COVID-19 vaccination and preeclampsia prevention. Understanding these mechanisms could lead to the development of new strategies for preventing and treating this serious pregnancy complication, even beyond the context of the COVID-19 pandemic.