HealthDay News — Messenger RNA (mRNA) from COVID-19 vaccines is not detectable in breast milk, according to a research letter published online July 6 in JAMA Pediatrics.

Yarden Golan, PhD, from the University of California in San Francisco, and colleagues analyzed milk samples to determine if vaccine-related mRNA was detectable in human milk after a COVID-19 vaccination. Samples from 7 lactating women were collected prior to vaccination (the BNT162b2 [Pfizer] and mRNA-1273 [Moderna] vaccines) and at various time points up to 48 hours after vaccination.

The researchers report that analysis of 13 human milk samples collected 24 hours after vaccination, including multiple time points (4 to 48 hours) from a single woman, showed that none of the samples had detectable levels of vaccine mRNA in any component of the milk.

“These results provide important early evidence to strengthen current recommendations that vaccine related mRNA is not transferred to the infant and that lactating individuals who receive the COVID-19 mRNA-based vaccine should not stop breastfeeding,” the authors write. “In addition, any residual mRNA below the limits of detection in our assay would undergo degradation by the infant gastrointestinal system, further reducing infant exposure.”


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