Up until now, there is no evidence that indicates that babies receive SARS-CoV-2 infection through breastmilk. A recent study has revealed that milk from a lactating mother contains SARS-CoV-2 antibodies. The detection of antibodies in breastmilk suggests that mothers transfer immunity to babies and not the infection.
Rebecca Powell, an immunologist at the Icahn School of Medicine at Mount Sinai in New York City, investigated the SARS-CoV-2 immune response in breastmilk. Initially, milk from 15 lactating mothers who were breastfeeding and had either recovered from Covid-19 infection or were suspected to have Covid-19 was analyzed. Researchers compared two data sets, i.e., a) breastmilk collected during the pandemic and b) breastmilk from different lactating mothers before the pandemic began. They analyzed the presence of immunoglobulin A (IgA) antibodies and the presence of antibodies to SARS-CoV-2 spike protein. Their study revealed that samples, collected from the women who had recovered from COVID-19, contained specific SARS-CoV-2 binding activity. However, the pre-pandemic samples contained low levels of nonspecific or cross-reactive antibodies.
Another study also reported a similar result. In this study, scientists collected breastmilk samples from women who tested negative for SARS-CoV-2 at the time of sample collection. They also collected general health information on the donors of the milk samples. The researchers concluded that the levels of S1 and S2 SARS-CoV-2–reactive IgG levels were higher in the breastmilk from women who suffered a viral respiratory infection during the last year when compared to the breastmilk of women who did not undergo a similar infection. This result implies that these immune responses could be due to the cross-reactivity from antibodies generated after exposure to other viruses. Also, the majority of the breastmilk samples that were collected during the pandemic contained high levels of IgA. Their IgG and IgM also reacted to the S1 and S2 subunits of the SARS-CoV-2 spike protein. Veronique Demers-Mathieu, an immunologist at Medolac Laboratories in Boulder City, Nevada, stated that the antibodies produced in breastmilk offer wide-ranging immunity to breastfeeding babies.
The breastmilk antibodies (specific or nonspecific to the virus) are secreted by the B cells. The secreted IgA is then shuttled from the mammary tissue to the milk via a transporter protein. These proteins encapsulate the antibodies, thereby, protecting them from being degraded in the infant’s mouth and gut.
Dr. Powell explained the advantage of the breastmilk-derived antibodies over blood-based antibodies for therapeutics. She said antibodies (IgG) isolated from serum and introduced to the Covid-19 patient is not a full-proof process as these might not reach the target site. However, secretory antibodies (IgA) extracted from breastmilk, would reach the target site without any hindrance because, these antibodies can be inhaled into the respiratory tract, the immediate target site for Covid-19 infection. Also, these secretory antibodies remain active in mucous.
Dr. Powell further reported that breastmilk antibodies could neutralize coronavirus. Currently, she has partnered with Lactiga to further her research and develop antibodies from breastmilk to fight COVID-19.