Reassuring news for women who are pregnant and unsure if they should get the vaccine.

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A South Florida frontline health care worker got her first shot of the Moderna COVID-19 vaccine when she was 36 weeks pregnant. Three weeks later, before receiving the second dose, she gave birth to a healthy baby girl who tested positive for COVID-19 antibodies. The news is significant, because it suggests that when a pregnant woman gets the vaccine, she can pass on protective antibodies to her newborn.

The case is documented in a preprint (i.e. not yet peer-reviewed) study by Paul Gilbert, MD, and Chad Rudnick MD, who are both affiliate professors at Florida Atlantic University. The antibodies were detected immediately after the baby was born following an analysis of blood from the umbilical cord, and antibodies were detected again before delivery of the placenta, according to the study.

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Credit: Getty Images / Design by Jo Imperio

"We have demonstrated that SARS-CoV-2 IgG antibodies are detectable in a newborn's cord blood sample after only a single dose of the Moderna COVID-19 vaccine," the authors wrote. "Thus, there is potential for protection and infection risk reduction from Sars-CoV-2 with maternal vaccination."

The baby girl, whose birth month wasn't included in the study, is believed to be the first in the US to be born with coronavirus antibodies. 

What are antibodies, and why are they important?

"Antibodies are proteins that are synthesized by the immune system against something it identifies as foreign," infectious disease expert Amesh A. Adalja, MD, senior scholar at the Johns Hopkins Center for Health Security in Maryland, tells Health.

Antibodies coat pathogens (such as viruses), which facilitates their clearance from the body, Dr. Adalja explainsThey also block the pathogen's ability to bind to receptors on cells—and if they don't bind to those cells, they can't infect the body, he adds. Antibodies also tend to stick around in the body, offering protection from reinfection with the same illness.

Scientists already knew that mothers who were infected with COVID-19 can transfer antibodies to their babies. And other vaccines—including the flu shot—are known to carry antibodies from mom to baby via the placenta. 

Does this mean pregnant women should get the vaccine?

Getting the COVID-19 vaccine during pregnancy has been a huge talking point recently. Pregnant women weren't actively involved in late-stage clinical trials for any COVID-19 vaccines—including the Pfizer, Moderna, and Johnson & Johnson vaccines that are currently available in the US—so there is no clear picture of the safety and efficacy of the vaccines during pregnancy. And the authors of the preprint study do stress that more research is needed. 

But last month, Pfizer announced that it had launched the first large-scale trial of its vaccine on pregnant women, which is expected to finish by early 2023. Moderna hasn't yet started trials that focus on pregnancy, but the company has created a registry to track pregnant women who get their shots. Johnson & Johnson has said it plans to include pregnant women and their infants in further studies, as well as collect data on pregnant women via their own registry.

In the meantime, the new study may give pregnant women some reassurance about getting the COVID-19 vaccine. And other preprint studies support the findings. Massachusetts General Hospital studied 131 women (84 pregnant, 31 breastfeeding, and 16 non-pregnant), who all received the Pfizer or Moderna vaccines. The pregnant and lactating women exhibited equally strong immune responses as the control group—and antibodies were identified in the placenta and breast milk of every sample taken. 

Another pre-print study from Hadassah Medical Center in Israel found a strong supply of COVID-19 antibodies in 40 newborns whose mothers had received both doses of the Pfizer vaccine.

"I'm sure there are many babies who are being born with COVID-19 antibodies, and it's all terrific news," Rebecca C. Brightman, MD, a gynecologist in New York City and an assistant clinical professor of obstetrics, gynecology, and reproductive medicine at the Icahn School of Medicine at Mount Sinai, tells Health.

Dr. Brightman points out that the COVID-19 vaccine is recommended for pregnant women, as they're considered to be an at-risk group—and she's had patients who've received the vaccine during pregnancy. 

"I encourage all of my patients and any woman with questions regarding the vaccine in pregnancy to check out the website of The American College of Obstetricians and Gynecologists (ACOG) for the most up-to-date information and advice," Dr. Brightman adds. 

The information in this story is accurate as of press time. However, as the situation surrounding COVID-19 continues to evolve, it's possible that some data have changed since publication. While Health is trying to keep our stories as up-to-date as possible, we also encourage readers to stay informed on news and recommendations for their own communities by using the CDCWHO, and their local public health department as resources.

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