No serious COVID-19 vaccine side effects in breastfeeding moms, infants

Sept. 14, 2021

In a recent study, published in the online edition of Breastfeeding Medicine, researchers at University of California San Diego School of Medicine found that breastfeeding mothers who received either the Pfizer-BioNTech or Moderna COVID-19 vaccines reported the same local or systemic symptoms as what has been previously reported in non-breastfeeding women, with no serious side effects in the breastfed infants.

“A mother’s first concern is the safety of her child,” said Christina Chambers, PhD, MPH, Professor of Pediatrics at UC San Diego School of Medicine and Professor in the Herbert Wertheim School of Public Health and Human Longevity Science. “Our study, along with previous research, suggests the Pfizer and Moderna vaccines are not red flags for breastfeeding mothers and their infants.”

The results found that more than 85% of the 180 breastfeeding women in the study who received an mRNA COVID-19 vaccine reported temporary localized symptoms, such as pain, redness, swelling or itching at the injection site, and systemic side effects, including chills, muscle/body aches, fever and vomiting, with higher frequency following the second dose.

Additionally, following the second dose of vaccine, women who received the Moderna brand were significantly more likely to report symptoms. A small proportion of women following the first dose of either vaccine brand reported a reduction in milk supply, and significantly more women reported a reduction in milk supply following the second dose of Moderna.

“We want to emphasize that the reduction in milk supply was in a small subset of women and came back fully within 72 hours after vaccination. We also cannot be certain that the supply reduction was a side effect of the vaccine or another unknown factor,” said Chambers. “What we do know is that the vaccine is incredibly effective in providing protection from COVID-19, which has proven to be a devastating and serious virus with possible long-term side effects.”

Irritability and poor sleep were reported in some breastfed children, but no serious adverse events.

The breastfeeding women recruited for the study enrolled into the Mommy’s Milk Human Milk Research Biorepository at UC San Diego, which strives to understand the numerous benefits human milk offers at a molecular level and uses these findings to improve the health and development of all children.

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