Getting a COVID vaccine during pregnancy benefits fetal health, new University of KY study finds

New research co-authored by University of Kentucky researchers shows fetal benefits when a pregnant person is vaccinated against COVID-19.

The study, funded by a National Institutes of Health grant, was published in the American Journal of Obstetrics and Gynecology in late November. It followed a group of 121 women from March 2021 until June 2022, through pregnancy, delivery and up to a year after giving birth. Each participant received two rounds of the vaccine and a booster shot. Close to 90% of the cohort got the Pfizer-BioNTech vaccine.

Scientists from UK and Oregon Health and Science University monitored antibody levels via blood samples from the mother, their newborn, the umbilical cord and the mothers’ breast milk. Researchers found that antibodies from the vaccine “passively transfer from mother to fetus in utero, offering the most protection,” said Dr. Ilhem Messaoudi, chair of UK’s Department of Microbiology, Immunology and Molecular Genetics.

“So at birth, these babies had maternal antibodies in circulation, which is fantastic. Getting vaccinated during pregnancy not only protected the mom, but also now provided passive protection for their newborns who are not eligible for the vaccine,” she added.

Researchers then found a “dramatic increase” of antibodies in a mother’s breast milk, increasing two- to three-fold in the weeks following birth.

“There was a massive increase in antibodies, which was unexpected but great to see,” Messaoudi said. “You really needed the first two shots and the booster to achieve excellent protection, to have that very long-lived, durable immune response. Then the newborn is protected via antibody transfer in utero through the placenta and postnatal through breastfeeding.”

“We now have a really large number of studies on vaccinations in pregnant women,” she added. “They’ve all shown great safety, tolerability and immunogenicity, so we’ve hit the trifecta. The vaccines are safe and work. That’s what’s really important.”

This new study is the latest in a growing body of research that points to the safety and efficacy of vaccination during pregnancy, a time when one’s immune system is considerably weakened and puts a person at greater risk of severe COVID-19 infection.

In the fall of 2021, months after COVID-19 vaccines first became widely accessible, pregnant people were among the least vaccinated groups, according to the Centers for Disease Control and Prevention. Health care providers across the country sounded the alarm on the severe risks this low rate posed to mothers and fetuses, and reported a notable spike in severe COVID infections and subsequent hospitalization among this group that year, including in Kentucky. An unvaccinated pregnant person who gets COVID-19 also faces a greater chance of pre-term birth.

The latest study acknowledged an ongoing “high level of vaccine hesitancy among the pregnant population.”

“Vaccination decisions during pregnancy are often influenced by a primary goal of protecting neonatal health,” researchers wrote in the latest study. “Thus, the decision to vaccinate during pregnancy or to delay vaccination is shaped by knowledge about the impact of vaccine timing and duration of protection.”

The study’s conclusions show that the “best neonatal protection against (COVID-19) is for a pregnant person to receive the three-dose vaccination series at any point during pregnancy,” which allows for placental antibody transfer, and then to “subsequently breastfeed their children for at least six months, at which point infants are eligible for SARS-CoV-2 vaccination.”

Eight of the study’s 10 researchers work at the University of Kentucky, including Dr. Delphine Malherbe, Madison Blanton, Brianna Doratt, Heather True, Taylor McDonald, Caroline Beauregard and Reuben Adatorwovor.