Effectiveness of a third BNT162b2 mRNA COVID-19 vaccination during pregnancy: a national observational study in Israel

Abstract

The Centers for Disease Control (CDC) recommend a third dose of COVID-19 vaccine for pregnant women, although data regarding effectiveness during pregnancy are lacking. This national, population-based, historical cohort study of pregnant women in Israel, delivering between August 1, 2021 and March 22, 2022, aims to analyze and compare the third and second doses’ vaccine effectiveness in preventing COVID-19-related hospitalizations during pregnancy during two COVID-19 waves (Delta variant in the summer of 2021 and Omicron, BA.1, variant in the winter of 2022). Time-dependent Cox proportional-hazards regression models estimate the hazard ratios (HR) and 95% confidence intervals (CI) for COVID-related outcomes according to vaccine dose, and vaccine effectiveness as 1-HR. Study includes 82,659 and 33,303 pregnant women from the Delta and Omicron waves, respectively. Compared with the second dose, the third dose effectively prevents overall hospitalizations with SARS-CoV-2 infections, with estimated effectiveness of 92% (95% CI 83–96%) during Delta, and enhances protection against significant disease during Omicron, with effectiveness of 92% (95% CI 26–99%), and 48% (95% CI 37–57%) effectiveness against hospitalization overall. A third dose of the BNT162b2 mRNA COVID-19 vaccine during pregnancy, given at least 5 months after the second vaccine dose, enhances protection against adverse COVID-19-related outcomes.

Coronavirus Disease 2019 (COVID-19) Vaccination in Pregnancy

“…Finally, during the Omicron period, receiving a third vaccine dose resulted in significantly improved vaccine effectiveness against hospitalization compared with two doses only. 25 (Fig. 3).…”

COVID-19 vaccination is effective at preventing severe illness and complications during pregnancy

“… 2 , 3 Although pregnant women were excluded from COVID-19 vaccine clinical trials, limiting initial data on effectiveness in pregnancy, 4 other studies have shown that mRNA COVID-19 vaccines are effective in pregnant women. 2 , 3 Three studies of pregnant women, published in 2022, have assessed disease severity 5 and vaccine effectiveness 2 , 6 during the period of omicron variant predominance. Using population-level data among women from Scotland with SARS-CoV-2 infection during pregnancy, authors found that, compared with the period of delta variant predominance, the omicron period was associated with significantly lower risk of preterm birth and severe illness during pregnancy.…”

“… 5 In studies from the USA and Israel, monovalent mRNA COVID-19 vaccination was less effective during the omicron period than the delta period and effectiveness waned over time, particularly during the omicron period in pregnant women who had not received a COVID-19 booster vaccination. 2 , 6 …”

COVID-19 Disease in Under-5 Children: Current Status and Strategies for Prevention including Vaccination

“…Vaccine-induced antibody titers may be similar to those produced in non-pregnant women, with antibody production starting two weeks from the first dose [ 166 ]. Benefits of the vaccine for the mother include reduced risk of infection, lower maternal hospitalization, and need for intensive care admission [ 167 , 168 ]. Vaccination in pregnant women also benefits the neonate due to the passive transfer of antibodies.…”