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Researchers say antibodies begin showing up in breast milk within weeks of a COVID-19 vaccination. JENNIFER BOGLE/Stocksy
  • Researchers say a COVID-19 vaccine given to someone who’s breastfeeding can produce antibodies in breast milk within weeks.
  • They say the antibodies can help provide protection for infants against the disease.
  • They add that a clinical trial indicated there are few side effects from the vaccine to mothers or infants.

Vaccinated women who breastfeed can pass COVID-19 protection to their babies.

A new study published in the Journal of the American Medical Association (JAMA) found that a COVID-19 vaccination prompts a robust secretion of antibodies in breast milk for up to 6 weeks after vaccination.

Dr. Danelle Fisher, pediatrician and chair of pediatrics at Providence Saint John’s Health Center in Santa Monica, California, finds it “incredibly encouraging” that antibodies were found in infants several weeks out.

“We start by giving moms protection that we hope lasts and that they can pass on to the baby. And it looks like that’s what’s going on,” Fisher told Healthline.

The prospective cohort study took place in Israel between December 23 and January 15.

Although breastfeeding women weren’t included in vaccine trials, they were encouraged to get vaccinated.

Researchers wanted to find out if SARS-CoV-2 antibodies were secreted into breast milk. Their study involved 84 women who received 2 doses of the Pfizer-BioNTech vaccine 21 days apart.

They collected samples of breast milk before the first vaccine. Starting 2 weeks after the first dose, they started taking samples once a week for 6 weeks.

Just 2 weeks after the first vaccine, there was significant elevation in the level of anti–SARS-CoV-2-specific IgA antibodies. There was another spike in antibody levels after the second vaccine.

The researchers also investigated adverse events among the women and their infants.

Some women had side effects from the vaccines and four infants experienced fever, cough, and congestion after their mothers were vaccinated. Three cases resolved without treatment. One infant was treated with antibiotics.

None of the women or infants experienced serious adverse events during the study.

“The study’s conclusions are exciting,” said Fisher.

“This is one of the first studies to go from start to finish, not just grabbing random samples, but really tracking women who are part of the study. It was well constructed, well thought out, and well carried out,” she added.

According to the Centers for Disease Control and Prevention (CDC), COVID-19 vaccines aren’t considered a risk to infants during pregnancy or from breastfeeding.

Fisher said this study goes along with what many doctors have been encouraging pregnant and breastfeeding people to do.

“Get vaccinated because even a tiny fraction of protection is better than none. And there’s no vaccine for babies at this time. And we know how incredibly valuable breast milk is. You can’t get this kind of protection from formula,” she said.

This particular study involved only the Pfizer vaccine.

“We can probably extrapolate the results to the Moderna vaccine because the Pfizer and Moderna vaccines are incredibly similar in the way they provide protection,” said Fisher.

Both are messenger RNA (mRNA) vaccines.

“I can confidently say to patients that I highly recommend vaccines for everybody, especially pregnant and breastfeeding moms,” said Fisher.

“But I think we’re still a little ways out with the Johnson & Johnson vaccine, which has a different mechanism of action,” she continued.

Right now, administration of the Johnson & Johnson vaccine is on pause while rare adverse events are under investigation.

“Once Johnson & Johnson has done more safety testing, it may be just as good an alternative. They still have studies to do, which may be more enlightening in terms of passing antibodies to infants. Right now, we can make a very good case for Pfizer and Moderna for protection that spreads to infants,” explained Fisher.

As for how long antibodies against COVID-19 might last in infants, it’s an open question.

“We’re still talking about how long antibodies last in everybody,” said Fisher.

“Participants in the original Pfizer study are still having blood drawn at regular intervals in individuals who’ve been vaccinated. We don’t yet know if we’ll need boosters in 1, 2, or 5 years. But studies are really encouraging, and it will be fascinating to see how the information unfolds in the next 6 to 12 months. We just have to be patient,” she said.

Fisher urges everyone to reach out to healthcare professionals to learn more.

“If in doubt, ask your doctor. Obstetricians and pediatricians are happy to have those discussions, and we’re eager to spread good information,” said Fisher.