SARS-CoV-2 vaccine effectiveness in preventing confirmed infection in pregnant women

BACKGROUND. SARS-CoV-2 infection in pregnancy is associated with a higher risk of pregnancy-related complications and neonatal respiratory distress and hospitalization. Effectiveness of SARS-CoV-2 vaccines in pregnant women is not known. METHODS. All women with confirmed pregnancy who presented to the national referral hospital in Qatar between December 20, 2020, and May 30, 2021, with at least 1 SARS-CoV-2 test and not testing prior to pregnancy were included. We determined the vaccine effectiveness of mRNA vaccines in preventing confirmed SARS-CoV-2 infection during pregnancy using both cohort and test-negative case-control designs. Analyses were adjusted for age group, nationality, and gestational age. RESULTS. Among 4534 pregnant women, there were 407 vaccinated and 407 unvaccinated women in the matched cohort analysis. Vaccine effectiveness was 87.6% (95%CI 44.1%-97.2%) at least 14 days after the second dose. There were 386 test-positive and 834 matched women in the test-negative case control analysis. Vaccine effectiveness was 86.8% (95%CI 47.5%-98.5%) at least 14 days after the second dose. Adjustment for age, nationality, and gestational age yielded similar results for both designs. In the test-negative analysis, vaccine effectiveness at least 14 days after the first dose but before the second dose was 40.8% (95% CI 0.0%-80.4%). Of the 386 test-positive pregnant women, 74 cases were Alpha variant, 163 cases were Beta variant, and 156 cases were variants of unknown status. There were 9 severe or critical disease cases and no deaths in the test-positive pregnant women, all of whom were unvaccinated. CONCLUSION. The mRNA vaccines provide a high level of protection against documented SARS-CoV-2 infection, which supports the inclusion of pregnant women in vaccination campaigns.