Among 613 infants studied, the (VE) of maternal third doses during pregnancy against COVID-19 infection was 71%.
Maternal COVID-19 vaccination status was categorized into four groups: unvaccinated, second dose before pregnancy, second dose during pregnancy, and third dose during pregnancy.
Fifty-one infants developed COVID-19 infections, with three hospitalizations limited to those in the unvaccinated and second-dose-before-pregnancy groups.
The VE for the second dose during pregnancy was 1%, indicating limited effectiveness against infection.
In contrast, the VE for the third dose during pregnancy was 71%, suggesting a significant potential benefit for infants.
The study was conducted during the period of Omicron variant predominance.
Simplified
Maternal Coronavirus disease 2019 (COVID-19) vaccination during pregnancy enables transplacental antibody transfer; however, data on clinical effectiveness in infants are limited. We evaluated the BNT162b2 and mRNA-1273 (VE) of maternal second and third doses against COVID-19 in infants during Omicron predominance. This population-based cohort study in a Japanese municipality included infants born between January and August 2022. Maternal vaccination status at delivery was classified as unvaccinated, second dose before pregnancy, second dose during pregnancy, or third dose during pregnancy. Follow-up for COVID-19 outcomes - primary (infection) and secondary (hospitalization) - began at delivery and ended at the infant's 6-month birthday or September 25, 2022, whichever came first. Adjusted hazard ratios (HRs) were estimated using Cox regression, comparing the second dose during pregnancy with no vaccination and comparing the third dose during pregnancy with the second dose before pregnancy. VE was calculated as (1-adjusted HR) × 100%). We identified 613 infants: 234, 72, 181, and 126 whose mothers were unvaccinated, received the second dose before pregnancy, received the second dose during pregnancy, and received the third dose during pregnancy, respectively. Fifty-one infants developed an infection. Three hospitalizations occurred only among infants in the unvaccinated and second-dose-before-pregnancy groups. VE of the second and third doses against infection was 1% (95% confidence interval [CI]:-87% to 47%) and 71% (95% CI:-7% to 92%), respectively. This study indicates that a third dose during pregnancy may be effective in protecting infants from COVID-19 infection during Omicron predominance, while a second dose limited effectiveness.
Key numbers
71%
of Third Dose
Effectiveness against COVID-19 infection for infants whose mothers received a third dose during pregnancy.
1%
of Second Dose
Effectiveness against COVID-19 infection for infants whose mothers received a second dose during pregnancy.
3
Infant Hospitalizations
Total number of hospitalizations among infants during the study.
Full Text
We can’t show the full text here under this license.
