Since the beginning of the global pandemic caused by the virus SARS-CoV-2, which causes the disease COVID-19, a major concern has been how pregnant people and their fetuses are affected. The Center for Disease Control (CDC) warns that currently pregnant people are at an increased risk for severe illness from COVID-19, and that contracting the virus puts them at a higher risk for preterm birth and other adverse effects.
Thus, when vaccines to protect against COVID-19 became widely available starting around January 2021, there was a question as to whether it was safe for pregnant people to be inoculated. While pregnant people were not included in the original vaccine trials, data from pregnant women who did chose to receive the vaccine ultimately found that being inoculated was safe during pregnancy, leading the CDC to recommend vaccines for currently pregnant people.
While it has been deemed relatively safe for people to be vaccinated during their pregnancies, one major question remains: how protected from COVID-19 are the fetuses once they are born?
New research from a team at Weill Cornell Medicine suggests that pregnant people who receive the vaccine during their pregnancies are able to pass appropriate antibodies to their fetuses. 122 people who self-identified as receiving either one or both doses of either the Moderna or Pfizer-BioNTech vaccine were studied, and results suggest that maternal antibodies were present as early as 5 days post-inoculation. Of the participants who received both doses, 99% had detectable antibodies by 4 weeks post-inoculation. For those who received only one dose, 45% had detectable antibodies. These findings suggest that pregnant people should get the vaccine as early as possible to allow adequate time to develop and pass antibodies.
Breastfeeding people were also excluded from the initial vaccine studies, and it has been questioned whether it was safe for infants to consume breastmilk from their vaccinated mothers. A new study led by Kathryn Gray from Brigham and Women’s Hospital found that lactating people had the same antibody response as non-lactating people. Moreover, a follow-up study from the University of San Francisco—still in preprint, or not yet peer reviewed—found that antibodies increased after the second dose of the vaccine. Importantly, the study found that the vaccine itself does not transfer, meaning that the infant would not be at an increased risk for receiving an active virus as they would with the yellow fever vaccine, for example. This means, only the antibodies that protect against infection from SARS-CoV-2 are transferred via breastmilk to infants.
The findings from these recent studies have led the World Health Organization to recommend the vaccine for both pregnant and lactating people—an important step in building herd immunity against the virus SARS-CoV-2.
Sources: Center for Disease Control (increased risk); Center for Disease Control (vaccine recommendation); Obstetrics and Gynecology; Weill Cornell Medicine; American Journal of Obstetrics and Gynecology; Nature; medRxiv; Science Daily