Pregnant and Breastfeeding Moms Can Pass Covid-19 Antibodies to Babies

Early data on the Pfizer and Moderna vaccines helps fill in major gaps in what scientists know about getting vaccinated for Covid-19 while pregnant. 

(CN) — Pregnant and breastfeeding moms have a good antibody response to the coronavirus vaccine, and can pass antibodies to their babies, according to a new study presenting the first data of its kind. 

The study involved 131 women of reproductive age, split into three groups: pregnant (84 people), lactating (31 people) and non-pregnant (16 people). Each of the participants received either the Pfizer or Moderna vaccines — neither of which were tested on pregnant people during clinical trials. 

Antibody levels were equivalent in all three groups, the researchers reported, as were post-vaccine side effects, which remained rare. From the initial results, it seems pregnant women’s antibody response is similar to that of non-pregnant people. 

Through both breast milk and umbilical cord blood, pregnant and lactating moms were also able to pass along their Covid-19 protection to their babies, the researchers discovered. 

The results were published Thursday in the American Journal of Obstetrics and Gynecology. 

Data has been virtually nonexistent as to how the Covid-19 vaccines may be different in pregnant women, making the new study an important part in moving toward vaccinating as much of the country as possible. 

“When the vaccine came out, it had not been given to any pregnant or breastfeeding women,” said Dr. Kathryn Gray, who specializes in maternal fetal medicine at Brigham and Women’s Hospital, during a phone call. 

“So our goal was to provide the first data to understand what pregnant and lactating women’s response would be when they received the vaccine,” and to see if antibodies could be passed on to babies, she said. 

Gray was the first author of the study, which involved researchers from Harvard, MIT, Massachusetts General Hospital and the Ragon Institute. 

The study authors urged future vaccine trials to include pregnant women, and said their study demonstrates a willingness to participate. Moderna began enrolling pregnant women in its trials at the end of February. 

With these results, pregnant people finally have some clear data to consider when deciding whether a vaccine is the right choice for them. 

Gray pointed out that an estimated 30,000 health care workers, one of the most vulnerable groups for Covid-19 exposure, are pregnant. And pregnant people can become sicker from the virus, with longer-lasting symptoms, compared with the general population 

“There was really nothing known when a lot of pregnant women had to decide if they were going to get the vaccine or not,” Gray said. The new study “allows women to have some information to sort of weigh the risks and benefits of receiving the vaccine while pregnant or lactating.” 

The word “some” may be key; the study does not fully answer the question of whether pregnant women are at increased risk for vaccine side effects. Questions remain, too, about whether there are any risks to the baby associated with the vaccine, either during pregnancy or breastfeeding. 

There’s also the question of the Johnson & Johnson vaccine, which was not used in the study. 

Gray noted, however, that the J&J vaccine, based on a weakened adenovirus, is “more similar to the types of vaccines that we have given to pregnant women for a long time.” The Pfizer and Moderna vaccines, by comparison, rely on an mRNA-based new technology. 

As more studies continue, the data may elucidate the best practices for vaccination during pregnancy, like whether there is an optimal trimester for the greatest protection and safety. 

Currently, the Centers for Disease Control and Protection says that getting a vaccine is a personal choice for those who are pregnant, recommending discussing the decision with a health care provider. 

“Based on how these vaccines work in the body, experts believe they are unlikely to pose a specific risk for people who are pregnant,” the CDC website reads. “However, there are currently limited data on the safety of Covid-19 vaccines in pregnant people.”

Using its V-Safe smartphone app, the CDC is tracking survey-based data on the health of those who are pregnant and received a vaccine. The first round of data from the program, released in February, did not highlight any safety signals for pregnant people. 

Thursday’s results don’t seem to signal that there should be a change in the CDC’s guidance for vaccination during pregnancy, Gray said: “I think they just provide more data to support what they’ve been saying.” 

Each person should do their own risk-benefit analysis based on the limited data, recognizing that pregnant people may be at particular risk of illness from the coronavirus. 

“Every person has to take that data into account, and make the best decision for themselves,” Gray said. “It just adds to the data that women have to make an informed decision. And hopefully more and more of that will be coming.” 

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