Study Finds COVID-19 Vaccination During Pregnancy Elicits Antibodies At Birth


The findings suggest that pregnant women should not delay COVID-19 vaccination until late pregnancy.

New research has found that COVID-19 vaccination of pregnant women elicits levels of antibodies to the SARS-CoV-2 spike protein at the time of delivery that do not vary dramatically depending on the timing of the vaccination. These findings suggest that delaying vaccination until after birth is not necessary, according to a Weill Cornell Medicine press release.

CDC recommendations currently advise that pregnant women receive COVID-19 vaccinations, and studies have suggested that COVID-19 tends to be more severe for women when they are pregnant. It also increases the risks of preterm birth, stillbirth, and other adverse fetal outcomes. Antibodies from COVID-19 vaccination cross the placenta to circulate in infants’ blood after delivery, and studies of the most commonly used vaccines so far have found no increased rate of adverse effects for mothers or babies, according to the study authors.

In the study, researchers analyzed how anti-spike antibody levels in the mother’s blood and infant’s umbilical cord blood at delivery varied with the timing of prior vaccination in nearly 1400 women and their newborns. They found that the levels of these antibodies at delivery tended to be higher when the initial vaccination course occurred in the third trimester.

However, the researchers also found that antibody levels at delivery are still comparably high, and probably still protective, when vaccination occurs in early pregnancy or even a few weeks before pregnancy. Furthermore, a booster shot late in pregnancy can make those antibody levels much higher, according to the study authors.

“Women often ask what is the best vaccination timing for the baby—our data suggest that it’s now,” said Malavika Prabhu, MD, an assistant professor of obstetrics and gynecology at Weill Cornell Medicine, in the press release.

The study was designed to identify the best timing for COVID-19 vaccination during pregnancy, and the analysis covered 1359 pregnant women who reported vaccination against COVID-19 during or up to 6 weeks before pregnancy. All participants gave birth at the New York-Presbyterian/Alexandra Cohen Hospital for Women and Newborns after 34 or more weeks of gestation.

According to the press release, the researchers found that anti-spike antibodies were generally detectable at delivery, in maternal and cord blood, among all the fully vaccinated women regardless of the timing of their first vaccine dose. Among women with no history of SARS-CoV-2 infection who received the 2-dose Pfizer or Moderna mRNA vaccines, the levels of antibodies at delivery were lowest if they were vaccinated before pregnancy or during their first trimester.

Antibody levels were highest, however, for third trimester vaccination, although the difference was not large. The investigators found no significant difference in anti-spike antibody levels by timing of vaccination among the relatively small number of women who received the Johnson & Johnson single-dose vaccine.

“The message here is that you can get vaccinated at any point during pregnancy and it is likely going to be beneficial to you and your baby at the time of birth—and of course by getting vaccinated early you will be protecting yourself and your baby throughout the pregnancy,” said first author Yawei Jenny Yang, PhD, MD, in the press release.

Women who had a prior history of COVID-19 infection had anti-spike antibody levels that were moderately higher on average and showed even less of a decline with earlier vaccination timing. Twenty of the women reported having a booster dose in the third trimester. On average, they had even higher levels of antibodies in maternal blood and cord blood, according to the study.

In women who did not receive a complete course of vaccination by the time of birth, the levels of anti-spike antibodies in maternal blood and cord blood were significantly lower than all other cohorts, including the earliest vaccinated cohort. Taken together, these findings suggest that pregnant women should not delay COVID-19 vaccination until late pregnancy, according to the study.

“These study results are consistent with what we see with other maternal vaccines such as flu and Tdap, which, when given during pregnancy, protects the mother and baby,” said senior author Laura Riley, MD, chair of the Department of Obstetrics and Gynecology at Weill Cornell Medicine, in the press release.


New Study Finds That the Best Time for COVID-19 Vaccination During Your Pregnancy May Be Now. News release. Weill Cornell Medicine; December 28, 2021. Accessed January 26, 2022.

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