Why It’s Important for Pregnant People to Get a Second COVID-19 Shot

Pregnant woman receiving a COVID vaccine.

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Key Takeaways

  • Researchers found that after the first dose of a COVID-19 mRNA vaccine, pregnant women had a lower antibody count when compared to their non-pregnant counterparts.
  • Pregnant and lactating people are more susceptible to infections during this period because the body is making adjustments to the immune system to accommodate the growing fetus.
  • Getting fully vaccinated is crucial for pregnant and lactating people.

If you’re pregnant, getting that second dose of an mRNA COVID-19 vaccine is key. New research shows that pregnant women responded slower to the first vaccine dose compared to non-pregnant women.

The October study, published in the Science Translational Medicine journal, underscores that two doses of the vaccine are necessary for pregnant or lactating people in order to achieve comparable immune responses to non-pregnant people.

“There are some differences between pregnant individuals in terms of the types and functions of the antibodies,” Kathryn Gray, MD, PhD, assistant professor at Harvard Medical School and the study’s co-author, tells Verywell. “The sort of maturation of this antibody profile is delayed in pregnant individuals, emphasizing that it’s very important to complete both doses of mRNA vaccines in order to achieve the full antibody response that you would hope for from the vaccine.”

The Second Dose Is Crucial

Gray and other researchers initiated this study after noticing that pregnant and lactating people were initially left out of COVID-19 vaccine trials.

“When the vaccine was first released, there was no data on pregnant and lactating individuals because they had been excluded from the initial vaccine studies,” Gray says.

The team analyzed antibodies from 84 pregnant, 31 lactating, and 16 non-pregnant women of the same age.

Participants were enrolled at the time they were about to get the vaccine. Their blood samples were drawn at baseline for comparison. The second blood draw was taken after the second dose of the vaccine.

“So we were looking across the doses from baseline to see what the antibody response was,” Gray says.

After the first dose, pregnant women had developed a lower amount of antibodies compared to their non-pregnant counterparts.

The study also identified key differences in vaccine response among pregnant and lactating individuals. After the second dose, lactating women had higher activity of killer cells—cells that can identify and kill cells infected with a virus.

According to Andrea Edlow, MD, MSc, assistant professor of obstetrics and gynecology at Harvard Medical School and investigator at the Massachusetts General Hospital, these cells play a key role in the innate immune response by killing virally infected cells.

"We found that the second vaccine or boost dose was critical to the presence of highly functional antibodies in the blood and breastmilk of lactating individuals,” Edlow said in a press release

What This Means For You

Vaccines are safe for pregnant and lactating people. Experts recommend those individuals get fully vaccinated to protect themselves and their babies. To locate a vaccine near you, enter your zip code at

Pregnant People Should Get Vaccinated

The implications of this study align with the Centers for Disease Control and Prevention's (CDC) recommendations for pregnant and lactating people. 

The CDC recommends that all pregnant people, people who are actively breastfeeding, and individuals trying to get pregnant get vaccinated. They also note:

  • COVID-19 vaccines do not contain the live virus and cannot cause infection in pregnant people or their babies
  • Early data shows the Pfizer-BioNTech and Moderna’s COVID-19 vaccines are safe during pregnancy 
  • Early data suggests that getting vaccinated during pregnancy can reduce the risk of infection
  • Vaccination helps pregnant people build antibodies to protect their baby 

“What we worry about with pregnant individuals is that when they get COVID, they’re much more likely to get severe disease, to be hospitalized, to be in the ICU, and more likely to die than their non-pregnant counterparts,” Gray says.

Because women’s bodies are making immunological adaptions and changes to allow the fetus to grow, it makes them more susceptible to infections from pregnancy through the lactation period. There are also potential implications for their pregnancy.

“There’s an increased risk of adverse pregnancy outcomes,” she adds. When pregnant women get COVID, they are at a higher risk for experiencing pregnancy loss, preterm delivery, and hypertension in pregnancy.

The bottom line? “Pregnant people should get the vaccine,” Gray says. “It’s important for them to get both doses.”

The information in this article is current as of the date listed, which means newer information may be available when you read this. For the most recent updates on COVID-19, visit our coronavirus news page.

2 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
  1. Atyeo C, DeRiso EA, Davis C, et al. COVID-19 mRNA vaccines drive differential antibody Fc-functional profiles in pregnant, lactating, and nonpregnant women. Sci Transl Med. 2021;13(617):eabi8631. doi:10.1126/scitranslmed.abi8631

  2. Centers for Disease Control and Prevention. COVID-19 vaccines while pregnant or breastfeeding.

By Kayla Hui, MPH
Kayla Hui, MPH is the health and wellness ecommerce writer at Verywell Health.She earned her master's degree in public health from the Boston University School of Public Health and BA from the University of Wisconsin-Madison.