Researchers aimed at ascertaining the long-term effect of parental COVID-19 infection vs vaccination on human milk antibody composition and functional activity via comparing temporal IgA and IgG response in human milk and microneutralization activity against SARS-CoV-2 between lactating parents with infection and vaccinated lactating parents out to 90 days after infection or vaccination.

• This cohort study involved a convenience sample of 47 lactating parents with infection and 30 lactating parents who were vaccinated.

• There was IgA dominance and great variability in antibody response in milk after infection while a robust IgG response was observed in correlation with vaccination, which began to decline by 90 days after the second vaccine dose.

• Neutralization activity against live SARS-CoV-2 virus was observed in milk from both groups, which can be attributed to IgA and IgG SARS-CoV-2 antibodies.

• Significant antibodies may appear in human milk following COVID-19 infection and vaccination, that exhibit different temporal patterns, but both neutralize live SARS-CoV-2 virus.