Messenger RNA (mRNA) vaccines against COVID-19 were recently approved under an emergency use authorization.¹ However, there is a paucity of data regarding vaccine safety in pregnant or lactating individuals who were excluded from phase 3 clinical trials,^2,3 and many mothers have declined vaccination or decided to discontinue breastfeeding (temporarily or permanently) due to concern that maternal vaccination may alter human milk. The World Health Organization recommends that breastfeeding individuals be vaccinated and does not advise cessation of breastfeeding following vaccine administration.^4,5 The Academy of Breastfeeding Medicine states that there is little plausible risk that vaccine nanoparticles or mRNA would enter breast tissue or be transferred to milk,⁶ which could theoretically result in priming of infant immune responses that could alter childhood immunity. However, there are no direct data. To address this knowledge gap, we analyzed milk samples to determine if vaccine-related mRNA was detectable in human milk after vaccination.