Breast-milk antibodies are different in both function and composition. Rather than enter the bloodstream, says Yariv Wine, an immunologist at Tel Aviv University who is conducting research on the breast milk of vaccinated parents, these antibodies “aim to especially protect the entry points to the body. They target what we call mucosal tissue — the respiratory tract, our oral cavity, our gut lining.” That COVID-19 is a respiratory virus has made researchers optimistic about breast milk’s effects. But there are lots of ways this process can be diluted. First of all, Wine noted, the vaccine itself is highly effective, but it’s not 100 percent effective even in those who have received it directly. It’s easy to forget that the stated goal of the vaccines was preventing “severe disease,” not eliminating infection. Indeed, Gorsky herself tested positive for the virus, with mild symptoms, despite being fully vaccinated. And immune response in milk itself varies by person. “One possibility is that the vaccine did not induce a sufficient level of antibodies in the breast milk,” said Wine. “We saw women in our study cohort for whom the levels of antibody in the breast milk were reduced compared to other women,” about one or two out of ten.