Human Milk Antibodies Elicited by BNT162b2 Vaccination have reduced activity against SARS-CoV-2 Variants of Concern

We detected the presence of SARS-CoV-2 specific IgA against all major VOCs in milk out to 6 weeks after D2 of BNT162b2. These likely confer some protection to the breastfed infants, who are ineligible for vaccination and are at risk of severe COVID-19.

However, we detected significantly reduced milk IgA binding to VOCs, including the globally dominant Delta variant, suggesting reduced protection for breastfeeding infants. Additionally, these antibodies were significantly reduced by as early as 4-6 weeks after D2.