COVID-19 Vaccination in Pregnancy Reduces Preeclampsia Risk, Studies Show
New research from 18 countries shows COVID-19 vaccination during pregnancy, particularly with booster doses, significantly reduces the risk of preeclampsia and other serious complications for both mothers and babies.
COVID-19 vaccination during pregnancy may lower the risk for preeclampsia and other complications, according to new data from a large international study. The findings 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.
In an analysis published in eClinicalMedicine, researchers evaluated the data of 6,527 pregnant women across 18 countries enrolled in the INTERCOVID Consortium cohort between 2020 and 2022. They compared vaccinated and unvaccinated women, with and without SARS-CoV-2 infection, to determine the impact of vaccination on preeclampsia.
Among the cohort, 33.2% were diagnosed with COVID-19 and 57.5% were unvaccinated. Of vaccinated women, 64.7% received mRNA COVID-19 vaccines and 30.6% received the initial vaccine plus a booster dose. Of the latter, 66.6% received a booster with an mRNA vaccine.
The researchers found that SARS-CoV-2 infection during pregnancy raised the risk for preeclampsia by 45% (adjusted OR = 1.45; 95% CI, 1.15-1.84) and by 78% (aOR = 1.78; 95% CI, 1.31-2.42) among unvaccinated women.
Vaccination reduced the risk for preeclampsia (aOR = 0.85; 95% CI, 0.65-1.1), especially if there was a booster dose (aOR = 0.67; 95% CI, 0.45-0.99). Vaccination with a booster dose lowered preeclampsia risk by 58% (aOR = 0.42; 95% CI, 0.2-0.87) among women with prior comorbidities like diabetes, thyroid disorders or hypertension.
Researchers found this effect was mainly seen in women diagnosed with COVID-19, and adjusting for study sites and cohort year did not change the magnitude of the effects. Although the preeclampsia odds reduction provided by vaccination remained significant after adjusting for SARS-CoV-2 infection, it was greater among women diagnosed with COVID-19.
COVID-19 vaccination also demonstrated protection against some other adverse outcomes, including preterm delivery, maternal morbidity and mortality and severe perinatal morbidity and mortality. This protection was stronger if the women also received a booster dose. Among these women, the risks were reduced by 33% (aOR = 0.67; 95% CI, 0.53-0.85) for preterm birth; 32% (aOR = 0.68; 95% CI, 0.55-0.83) for maternal morbidity and mortality; and 29% (aOR=0.71; 95% CI 0.54-0.95) for severe perinatal morbidity and mortality.
The findings should be interpreted with caution because of the observational nature of the study, the risk of selection bias related to vaccination uptake, possible residual confounding and the risk of overstating results without statistical significance with reduced power in stratified analyses.
A second study led by researchers from the US Centers for Disease Control and Prevention involved the assessment of miscarriage risk during 6 to 20 weeks' gestation among women who received at least one dose of the monovalent (single-strain) mRNA COVID-19 vaccine up to a month before their last menstrual period or during pregnancy. The researchers analyzed data from the CDC's COVID-19 Vaccine Pregnancy Registry on 12,907 pregnancies among women aged 18 to 54 years from December 2020 to June 2021.
Most participants were White (79.1%), in their 30s (77.3%), and had received two doses of an mRNA COVID-19 vaccine (93.7%), 58.5% of whom received the Pfizer vaccine. The cumulative risk of miscarriage was 10.8%, with similar risk in both Moderna and Pfizer vaccine recipients. The findings, published in Vaccine, are an update on a 2021 preliminary report based on early, incomplete data.
Several recent studies have demonstrated both the safety and benefits of prenatal COVID-19 vaccination, which include lower risks for maternal hospitalization, preterm birth and stillbirth. These results go beyond the known benefits of COVID-19 vaccination in pregnancy, with evidence that maternal vaccination may influence pathways involved in preeclampsia development, suggesting a broader immunological or vascular benefit of vaccination.