WEDNESDAY, Feb. 25, 2026 (HealthDay News) -- COVID-19 vaccination, especially with a booster dose, is associated with reduced odds of preeclampsia (PE), according to a study published online Feb. 18 in eClinicalMedicine.Paolo Ivo Cavoretto, M.D., Ph.D., from IRCCS San Raffaele Hospital in Milan, and colleagues analyzed individual-level data from pregnant women prospectively enrolled from 18 countries in two consecutive cohorts between 2020 and 2022 during the COVID-19 pandemic to examine whether vaccination affects the risks for PE.Of 6,527 pregnant women, 2,166 (33.2 percent) and 3,753 (57.5 percent) were diagnosed with COVID-19 and were unvaccinated, respectively. Overall, 64.7 percent of the 2,774 vaccinated women received mRNA vaccines; 848 (30.6 percent) received a booster dose in addition to the initial regimen. The researchers observed an independent association between COVID-19 and PE (adjusted odds ratio, 1.45), especially in unvaccinated women (adjusted odds ratio, 1.78). Vaccination had a protective effect against PE during the index pregnancy, after adjustment for confounders (adjusted odds ratio, 0.85), which was stronger with a booster dose (adjusted odds ratio, 0.67). The odds were reduced among women with preexisting morbidities who received a booster dose (adjusted odds ratio, 0.42), which was mainly seen in women diagnosed with COVID-19. The magnitude of the effect was not altered with adjustment for study site and cohort year."We now have evidence that maternal vaccination may influence pathways involved in preeclampsia development, suggesting a broader immunological or vascular benefit of vaccination," senior coauthor José Villar, M.D., M.P.H., Ph.D., from the University of Oxford in the United Kingdom, said in a statement.Abstract/Full Text.Sign up for our weekly HealthDay newsletter