At least three studies have found that women who received either the Pfizer Inc.-BioNTech SE vaccine or the Moderna Inc. shots during pregnancy had coronavirus antibodies in their umbilical-cord blood. That indicates the women’s babies got the antibodies, too.
One of the studies also found antibodies in the breast milk of mothers who had received the vaccine during pregnancy.
The studies didn’t look specifically at the safety of vaccinations, though in one of them, pregnant women who were vaccinated didn’t report more side effects than those who weren’t pregnant.
Pregnant women are at higher risk of a severe case of Covid-19 and of preterm delivery if they are infected. The studies’ findings, though preliminary, suggest women could safely protect themselves and their newborns by getting vaccinated.
“Since infants can’t be immunized themselves, it’s one way for a pregnant individual to protect their newborn,” said Linda Eckert, a professor of obstetrics and gynecology at the University of Washington in Seattle, who wasn’t involved in the research.
As Covid-19 shots have rolled out, many pregnant women have struggled to decide whether to get immunized. Behind that struggle is uncertainty about how safe and effective the inoculations are for them and their babies.
Health authorities haven’t been able to provide the definitive guidance some pregnant mothers say they would like. The U.S. Centers for Disease Control and Prevention has said pregnant women may choose to be vaccinated if they wish.
Pfizer and BioNTech have begun administering their Covid-19 vaccine to pregnant women as part of a clinical trial studying the vaccine’s safety and efficacy in expectant mothers. The companies are now enrolling around 4,000 pregnant women into the trial, which will also look at the vaccine’s safety in infants and whether antibodies can get transferred over to them. The study should be completed by June 2022, Pfizer said.
Moderna said it is reviewing the recent research suggesting vaccine-generated antibodies transfer over to infants. The company also plans to carry out a study looking at the health outcomes of mothers who got the vaccine while pregnant and their infants.
Earlier studies reported that antibodies triggered by real-world infections crossed the placenta. There wasn’t evidence until the recent studies, however, indicating that expectant mothers could pass to fetuses the antibodies generated by vaccines.
Nor was there evidence until recently indicating that new mothers who were vaccinated could pass along antibodies through breast-feeding.
“I know now that something I’m doing is potentially helping to protect my child from getting sick,” said Christa Carrig, a Massachusetts General Hospital nurse and nursing mother who took part in the hospital’s recent study that found antibodies in the breast milk of lactating subjects. She received her second dose of the Moderna vaccine in early February.
Much remains unknown, including the best stage of pregnancy to administer a Covid-19 vaccine. Scientists are also still exploring how effectively vaccine-generated antibodies transferred by mothers protect infants from infection and illness.
Researchers explored vaccination’s impact on newborns partly by sampling the blood inside the umbilical cords of babies right after they were born. The scientists wanted to see if the cord blood contained Covid-19 antibodies. If it did, that meant the baby also had those antibodies because everything in the umbilical cord is shared between the mother and fetus.
In one recent study, Israeli researchers reported finding coronavirus antibodies in 20 vaccinated mothers. The study, which hasn’t yet been peer reviewed, was published March 12 on a preprint server.
Likewise, researchers in Florida said, in a case report published in the journal BMC Pediatrics on March 22, that they had found antibodies in the cord blood of a baby whose mother had received a first dose of the Moderna vaccine.
The Massachusetts General researchers looked in their study for antibodies in both cord blood and breast milk. The scientists reported finding coronavirus antibodies in the cord blood of all 10 mothers who gave birth during the study.
The study, which was published online by the American Journal of Obstetrics and Gynecology on March 25, also found signs that a fetus may get stronger protection against Covid-19 if the mother is vaccinated earlier in pregnancy.
Other studies looking at natural coronavirus infections in pregnant women had similarly found they transfer more antibodies to their fetuses the more time between the infection and delivery. The new study suggests the pattern holds for vaccine-generated antibodies, said Galit Alter, the lead immunologist on the study.
Dr. Alter and fellow researchers also found antibodies in the breast milk of all 31 lactating mothers enrolled in the study, suggesting babies could potentially continue receiving some form of immune protection through breast-feeding. The results corroborated several other studies that also found antibodies in breast milk.
Scientists suspect a particular type of antibody, known as IgA, plays a critical role providing protection against respiratory pathogens like the new coronavirus. It is especially prominent in breast milk.
Volunteers in the Massachusetts General study who received the second dose of the Moderna vaccine had higher levels of IgA antibodies in their breast milk than those who received both doses of the Pfizer vaccine, Dr. Alter said.
The reason is unclear, Dr. Alter said, but she suspects it could be because the interval between the first and second dose for the Moderna vaccine is longer—28 days—than that of the Pfizer-BioNTech vaccine, which is 21 days.
“It may be that Moderna confers enhanced protection in the context of lactating moms,” she said.
Nicole LeBoeuf, of Boston, is due in late August and enrolled in the study before getting the Pfizer-BioNTech vaccine earlier this year. She is glad she got vaccinated, she said, because it will help protect her child before Covid-19 vaccines are available for infants.
“Knowing that I could potentially protect this baby—I’m continuously reminded that this was the right decision,” said Dr. LeBoeuf, a dermatologist at the Dana-Farber Cancer Institute and Brigham and Women’s Hospital in Boston.
This story has been published from a wire agency feed without modifications to the text.