Association between BNT162b2 Vaccination and Incidence of SARS-CoV-2 Infection in Pregnant Women

Jama. published online July 12, 2021. doi: 10.1001 / jama.2021.11035

Commentary

The study was designed to evaluate the association between BNT162b2mRNA vaccination and the risk of SARS-CoV-2 infection in pregnant women.

Pregnant women vaccinated with the first dose between December 19, 2020, and February 28, 2021, were compared with unvaccinated women by age, weeks of pregnancy, region of residence, population subgroup, childbirth history, and influenza immunity status. They were matched 1:1 with unvaccinated women by Follow-up ended on April 11, 2021.

This cohort study included 7530 vaccinated and 7530 unvaccinated women with a mean age of 31.1 years (SD, 4.9 years). The rates were 46% and 33% in the second and third trimesters, respectively. With a median follow-up of 37 days for the primary outcome, there were 118 SARS-CoV-2 infections in the vaccinated group and 202 in the non-vaccinated group.

Among the infected women, 88 of 105 (83.8%) were symptomatic in the vaccinated group, whereas 149 of 179 (83.2%) were symptomatic in the unvaccinated group (P ≥.99). During the 28-70 day follow-up period, there were 10 infections in the vaccinated group and 46 in the unvaccinated group. The risk of infection was 0.33% versus 1.64% in the vaccinated and non-vaccinated groups, respectively, for an absolute difference of 1.31%. (95% CI, 0.89%-1.74%)

The adjusted hazard ratio was 0.22 (95% CI, 0.11-0.43). Vaccine-related adverse events were reported by 68 patients, none of which were serious.

The most commonly reported symptoms were headache (n = 10, 0.1%), general weakness (n = 8, 0.1%), unspecified pain (n = 6, <0.1%), and abdominal pain (n = 5, <0.1%).  In conclusion, in this backward cohort study of pregnant women, BNT162b2 mRNA vaccination compared to no vaccination was associated with a significantly lower risk of SARS-CoV-2 infection.