WEDNESDAY, April 21, 2021 (HealthDay News) — Antibodies to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) are detectable in the breast milk of lactating women up to 80 days following COVID-19 vaccination, according to a research letter published online March 30 in the American Journal of Obstetrics & Gynecology.

Jeannie C. Kelly, M.D., from Washington University in St. Louis, and colleagues characterized breast milk levels of anti-SARS-CoV-2 antibodies in five lactating individuals undergoing vaccination with the Pfizer-BioNTech/BNT162b2 vaccine. Participants provided frozen breast milk samples (29) prior to vaccination, within the first 24 hours of vaccination, and weekly following vaccination. SARS-CoV-2 RNA levels in breast milk were assessed using quantitative real-time polymerase chain reaction and anti-spike immunoglobulin (Ig)G and IgA by an enzyme-linked immunosorbent assay.

The researchers found that all prevaccine milk samples tested negative for SARS-CoV-2 RNA. At all time points thereafter, anti-spike IgG and IgA levels were significantly elevated versus prevaccine baseline. At 20 days after the first dose, anti-spike protein IgG remained sustained at a significant elevation compared with baseline. From baseline to the final sample, levels of anti-spike protein IgA were significantly elevated, but individual-level data suggested a possible gradual decline in anti-spike IgA in human milk over time following the second dose. “We’re now seeing a cascade of new data that indicate maternal vaccines are also going to help protect babies — both through transfer of antibodies through the placenta during pregnancy and through the breast milk during lactation,” Kelly said in a statement. “This is information we didn’t have a few months ago and it’s really helping us better counsel our patients who are considering getting the vaccine.”

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One author disclosed financial ties to pharmaceutical and medical companies.

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