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

Butt, Adeel A; Chemaitelly, Hiam; Al Khal, Abdullatif; Coyle, Peter V; Saleh, Huda; Kaleeckal, Anvar; Latif, Ali N; Bertollini, Roberto; Abou-Samra, Abdul Badi; Abu-Raddad, Laith J

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 one 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 4,534 pregnant women, there were 407 vaccinated and unvaccinated women in the matched cohort analysis. Vaccine effectiveness was 87.6% (95%CI 44.1-97.2%) ≥ 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) ≥ 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 ≥ 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 were Alpha variant, 163 were Beta variant, and 156 were variants of unknown status. There were nine severe/critical disease cases, and no deaths in the PCR-positive pregnant women, all among unvaccinated. CONCLUSIONS: The mRNA vaccines provide high level of protection against documented SARS-CoV-2 infection, which supports including pregnant women in vaccination campaigns.