Association of COVID-19 Vaccination Status With Hospitalization and Illness Severity Among Pregnant Women: A Nationwide Population-Based Study in South Korea.

During the COVID-19 pandemic, vaccination rates among pregnant women were notably lower due to concerns about vaccine safety and effectiveness. We investigated the impact of COVID-19 vaccination on hospitalization and illness severity due to COVID-19 among pregnant women. Data were obtained from the Korea Disease Control and Prevention Agency's COVID-19 National Health Insurance Service cohort, including 2,235 pregnant women and 6,733 nonpregnant women (1:3 matched) infected with COVID-19 between October 2020 and December 2021. COVID-19 vaccination status was categorized as unvaccinated, first dose only, and fully vaccinated (2 or more doses). Logistic regression was performed to identify factors associated with hospitalization and illness severity. Among pregnant women infected with COVID-19, 88.4% were unvaccinated, 4.6% received 1 dose, and 7.1% were fully vaccinated, compared to 61.3%, 8.1%, and 30.6%, respectively, for nonpregnant women. The odds ratio (OR) for hospitalization was significantly higher for pregnant women compared to nonpregnant women (OR=1.78). Within the pregnant women cohort, the OR for hospitalization was 0.92 for those who received the first vaccine dose and 0.37 for those who were fully vaccinated, demonstrating a significantly lower hospitalization rate only in the fully vaccinated group. A similar pattern was observed for illness severity, with ORs of 0.74 for the first dose and 0.33 for full vaccination, indicating a significantly lower rate of severe illness only in the fully vaccinated group. Additionally, high-risk pregnant women exhibited significantly higher odds of both hospitalization and severe illness. These findings demonstrate that full COVID-19 vaccination coverage (2 or more doses) is strongly associated with decreased hospitalization and severe illness among pregnant women. Addressing vaccine hesitancy through prenatal care discussions and improving vaccine accessibility is essential to enhance maternal health outcomes.