A woman receives a vaccination against COVID-19 at a temporary Clalit healthcare maintenance organisation (HMO) centre, at a basketball court in Petah Tikva, Israel January 28, 2021. REUTERS/Ammar Awad

An Israeli study found that vaccinated breastfeeding mothers produce antibodies in their breast milk for an extended period of time, possibly helping to protect infants from contracting COVID-19.

“Antibodies found in breast milk of these women showed strong neutralizing effects, suggesting a potential protective effect against infection in the infant,” according to the findings published in the Journal of the American Medical Association (JAMA). “This study found robust secretion of SARS-CoV-2 specific IgA and IgG antibodies in breast milk for 6 weeks after vaccination.”

The researchers of the study from Shamir Medical Center in Israel pointed out that although vaccine trials did not include the study of breastfeeding women and no other vaccine-related safety data had been published, nursing moms belonging to risk groups such as health workers have been encouraged to get immunized.

The cohort study published in the JAMA included 84 breastfeeding mothers in their 30s, who were healthcare workers recruited from different parts of Israel between December 23, 2020, and January 15, 2021, and who provided 504 breast milk samples. All participants received two doses of the Pfizer-BioNTech vaccine, 21 days apart. Breast milk samples were collected before administration of the vaccine and then once weekly for six weeks, starting at week two after the first dose. No mother or infant experienced any serious adverse event during the study period.

The research showed that after the first jab, mean levels of anti–SARS-CoV-2-specific IgA antibodies in the breast milk increased rapidly and were significantly elevated after two weeks — when 61.8% of samples tested positive for antibodies, increasing to 86.1% at week 4. Those levels stayed elevated for the duration of follow-up, the study concluded.

The research comes as, for now, COVID-19 vaccines have not been approved for infants. A few recent studies involving a smaller number of participants have also suggested that antibodies can be passed from mothers to their infants through breastfeeding. One, published on March 30 by the Washington University School of Medicine in St. Louis and involving five breastfeeding mothers, found that breastmilk contained elevated levels of the IgA and IgG antibodies immediately following the first dose of vaccination, with both antibodies reaching immune-significant levels within 14 to 20 days of first vaccination in all participants.