New Research Shows COVID-19 Booster Vaccination during Pregnancy May Provide Better Immune Response

Washington, D.C. — COVID-19 booster vaccination during pregnancy may provide better and longer protection from COVID-19 than receiving only the initial two-dose vaccination, according to a study released today in Obstetrics & Gynecology.

The study, "Maternal and Neonatal Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) Immunoglobulin G Levels After the Pfizer-BioNTech Booster Dose for Coronavirus Disease 2019 (COVID-19) Vaccination During the Second Trimester of Pregnancy," compared maternal and neonatal antibody levels after vaccination with the Pfizer-BioNTech vaccine for two large groups of pregnant women with similar demographic and clinical characteristics at a medical facility in Israel.

One group received a third (booster) vaccine at 17–30 weeks of pregnancy, and in a historical control group from a past study, participants received two doses of the Pfizer vaccine during that same gestational period. The findings showed significantly higher concentrations of maternal and infant antibodies at birth after a booster than after the primary two-dose vaccination.

"Up until this point, there has been limited data on the immune response of pregnant women after the third Pfizer vaccine dose during pregnancy," said Nir Kugelman, MD, the lead study author. "Although there is uncertainty as to whether antibodies correlate to immune protection, our findings support booster vaccination during pregnancy."

Another important finding was that while maternal and infant antibodies decline naturally over time, decline in maternal antibodies was much slower in the group that received the booster than the group that received the initial vaccine doses. The concentration of antibodies found in the umbilical cord blood may even suggest longer and better protection for infants as well.

"Placental transmission of COVID-19 antibodies has been proven in other studies," Kugelman said, "but in our study, we were able to find that the concentration of neonatal antibodies after booster vaccination in the second trimester was, on average, two times higher than the maternal antibody concentration. More research is needed, but this is encouraging news."

Current guidance from the CDC and the American College of Obstetricians and Gynecologists recommends that all individuals, including pregnant and recently pregnant people up to six weeks postpartum, receive a booster dose following the completion of their initial COVID-19 vaccine. Both organizations advise that initial and booster vaccination may occur in any trimester, and they recommend vaccine receipt as soon as possible to maximize maternal and fetal health.

"Currently, roughly 70% of pregnant people have been vaccinated, and 55% have received the booster," said study coauthor Shlomit Riskin-Mashiah, MD. "This study adds to the existing body of critical research on COVID-19 vaccine immune response and will hopefully help support more pregnant individuals in their decision to get vaccinated and boosted."

To read the study, visit Obstetrics & Gynecology.