• Posted February 20, 2026

COVID-19 Boosters Tied to Lower Preeclampsia Risk in Pregnant Women

Getting vaccinated against COVID-19 might offer protection against one of the most dangerous complications of pregnancy.

A large international study published online Feb. 18 in eClinicalMedicine followed more than 6,500 pregnant women across 18 countries. 

The findings linked COVID vaccination — especially with a booster dose — to a lower risk of developing preeclampsia, dangerously high blood pressure that can damage organs and threaten the lives of both mother and baby.

Preeclampsia affects roughly 3% to 8% of pregnancies globally. While its exact cause remains a bit of a medical mystery, doctors know it involves inflammation and issues with how blood vessels function. These are the same pathways affected by COVID-19.

The new study enrolled 6,527 pregnant women from 40 hospitals between 2020 and 2022. Pregnant women with a documented COVID diagnosis were matched to a control without COVID in the same hospital.  

Of the 2,774 vaccinated women included, 1,795 (64%) received mRNA vaccines; 848 (31%) also had a booster dose. Of those, 67% received a booster with an mRNA vaccine.

Researchers found that getting COVID during pregnancy increased the risk of preeclampsia by 45% overall. Among the unvaccinated, that risk jumped to 78%.

But for women who stayed current with their shots, the vaccine seemed to act as a shield. 

Vaccination was tied to a 33% lower odds of preeclampsia among those receiving a booster dose.

“Our results support the importance of strengthening COVID vaccination programs during pregnancy, emphasizing boosters and ensuring that pregnant people across the world have equitable access to the vaccine,” study co-author Dr. Jagjit Teji said in a news release. He’s a neonatologist at Lurie Children’s Hospital at Northwestern University Feinberg School of Medicine in Chicago. 

“We offer evidence from the first large study suggesting that COVID vaccination may protect against one of the most serious pregnancy complications,” he added.

Among women who never got sick, researchers found the shots appeared to improve vascular and immune health. For mothers with pre-existing conditions like diabetes or chronic high blood pressure, the booster dose was tied to a reduced preeclampsia risk of 58%.

Researchers say the vaccine may train the immune system to handle inflammation better, which helps the placenta and blood vessels stay healthy throughout the pregnancy.

Dr. José Villar is principal investigator of the INTERCOVID consortium, a multinational research group investigating COVID and its impacts on maternal, fetal and newborn outcomes. It’s based at the Oxford Maternal & Perinatal Health Institute in the U.K.

“We now have evidence that maternal vaccination may influence pathways involved in preeclampsia development, suggesting a broader immunological or vascular benefit of vaccination,” said Villar, a professor of perinatal medicine at the University of Oxford.

Beyond blood pressure, the study found that vaccinated women were also less likely to experience preterm births or severe complications during delivery.

Several authors reported ties to the pharmaceutical industry.

More information

The U.S. Centers for Disease Control and Prevention has guidance on COVID-19 vaccines while pregnant or breastfeeding.

SOURCES: Ann & Robert H. Lurie Children's Hospital of Chicago, news release, Feb. 11, 2026; eClinicalMedicine, Feb. 18, 2026