Several years after the SARS-CoV-2 pandemic, I still get questions about the efficacy and safety of the COVID-19 vaccine, including questions about getting the vaccine during pregnancy. Will it protect the baby against COVID-19 infection? And is it better to get a booster vaccine dose during pregnancy, or after delivery and rely on antibody transmission through breastfeeding?
After all, we particularly want infants to have these antibodies during those first 6 months of life, before they can receive the COVID-19 vaccine.
This week, an article that is being early released in Pediatrics, entitled “Infant Antibodies After Maternal COVID-19 Vaccination During Pregnancy or Postpartum,” by Flor Munoz, MD, from Baylor College of Medicine and colleagues from the MOMI-Vax Study Group, tackles these questions (10.1542/peds.2024-070175).
Between July 6, 2021, and January 31, 2022, the authors enrolled a prospective cohort of infants born to 3 groups of mothers:
- 280 mothers received 2 doses of COVID-19 mRNA vaccine (Pfizer or Moderna) during pregnancy at least 2 weeks prior to delivery.
- 202 mothers received 3 doses of COVID-19 mRNA vaccine shortly before or during pregnancy at least 2 weeks prior to delivery; these mothers were considered to have been “boosted” with the 3rd dose.
- 32 mothers were vaccinated postpartum with 2 doses of COVID-19 mRNA vaccine, with the last dose at least 2 weeks before the infant’s 2-month visit.
The authors then measured antibody titers in the mothers at the time of delivery and in the infants at birth, 2, and 6 months of age.
Of the 3 groups, the infants with the highest antibody titers were those born to mothers who received 3 doses during pregnancy, followed by those whose mothers who received 2 doses during pregnancy. Importantly, those whose mothers had 3 doses during pregnancy were likely to have antibody titers at 6 months, while infants whose mothers had 2 doses during pregnancy generally only had antibody titers at birth and 2 months. So the antibody titers were more long-lasting for those whose mothers had gotten the booster dose.
When the mother got the booster dose was also important; if it was later during pregnancy, the infant’s titers were higher at birth, which translated to higher likelihood of having titers at 6 months.
Infants were also more likely to have antibody titers at 6 months if their mother had had COVID-19 infection during pregnancy or if they had had infection during the first 6 months of life. Whether the infant was breastfed or formula-fed did not significantly affect the infant’s antibody titers.
This study supports giving pregnant mothers COVID-19 vaccine and giving a booster dose to those who have been previously vaccinated or had COVID-19 infection, as this boost optimizes antibody titers in infants and protects them through 6 months of life. And it’s better to vaccinate during pregnancy than to vaccinate after pregnancy and depend on antibodies from the breast milk.
