Pregnant or Breastfeeding Women Have a High Antibody Response After Vaccination

The largest study to date is more great news for pregnant people.

Last week, a research team from Brigham and Women’s Hospital and Massachusetts General Hospital published the largest study to date verifying the efficacy of Covid-19 vaccination during pregnancy. This new study helps the 3.7 million people who give birth in the United States per year find answers to their questions about getting the Covid-19 vaccine and pregnancy.

The American College of Obstetricians and Gynecologists and other women’s health experts agree that Covid-19 vaccines should be offered to those who are pregnant or breastfeeding. Though pregnant people were excluded from the initial Covid-19 vaccine clinical trials, obstetricians and gynecologists, like me, follow the latest research to help our patients make safe decisions regarding their pregnancy.

The Boston research team published their study, titled “Covid-19 vaccine response in pregnant and lactating women,” in the American Journal of Obstetrics and Gynecology (AJOG). Their findings are consistent with several other small studies showing that pregnant people have a robust antibody response after getting a Covid-19 vaccination and that they secrete the antibodies into their breast milk.

This study is important verification that pregnant women also develop an appropriate antibody response after vaccination.

This study analyzed blood samples and breast milk from 131 women in Boston and the surrounding area. The study included 84 pregnant, 31 lactating, and 16 nonpregnant people as well as five women who reported a previous infection with Covid-19. Each person received the two-dose series of the Pfizer or Moderna Covid-19 vaccine, following the protocols approved by the Food and Drug Administration (FDA).

The research team tested each person’s blood and breast milk before vaccination and monitored their antibody response. The scientists compared antibody levels in pregnant women with 37 individuals with a history of natural infection during pregnancy and a cohort of nonpregnant people.

The results indicated a robust blood antibody response in all three groups. While scientists have shown already that moms pass protective antibodies to their baby after a natural Covid-19 infection, this study is important verification that pregnant women also develop an appropriate antibody response after vaccination.

Antibody transfer is good news for babies: A newborn’s immune system is not fully developed, so babies rely on maternal antibodies from blood and breast milk to protect against various infections during the first few months of life.

This study also reinforced encouraging news for lactating people. All the vaccinated mothers had antibodies in the breast milk samples. This finding provides further evidence that vaccinated women pass protective antibodies to their babies. Antibodies are present in breast milk within five to seven days of other viral vaccinations such as Tdap and influenza. Previous research also demonstrated that women with a natural Covid-19 infection produce antibodies and secrete them into their breast milk. This study confirms published data showing vaccinated women do too.

The side effects reported in the study were rare and similar in all three groups. The most common symptoms were fever and chills. These side effects are known to be good signs the vaccines are working to trigger an immune response.

This paper adds to the growing body of evidence supporting the safety and efficacy of Covid-19 vaccination in pregnancy and lactation. We continue to learn more about the novel coronavirus’s effects on pregnancy, newborns, and Covid-19 immunization in pregnancy.

Current research shows that most pregnant people who contract Covid-19 have excellent outcomes but have an increased risk of ICU admission and preterm labor. Based on the known risks of Covid-19 infection in pregnancy, pregnant and lactating people are eligible for any one of the three FDA-approved vaccines.

None of those vaccines contain a live virus. It’s important to remember that you cannot catch Covid-19 from the vaccine or spread the disease from the vaccines to a newborn through breastfeeding.

Pregnant patients can be confident knowing the three approved vaccines trigger an immune response to help protect themselves and their babies.

Pregnant and lactating individuals are categorized as 1B in most states and1C in others. To find a Covid-19 vaccine near you, click here.