Data show that breastfeeding women infected with Covid-19 continue to secrete virus neutralizing antibodies into their milk for up to 10 months.
Besides emphasizing the important role that breastfeeding can play in helping protect children from disease, researchers believe that such antibodies could be used to treat people with severe Covid-19, preventing their condition from getting worse.
Although young children are less likely to develop severe Covid-19 than older adults or those with underlying health conditions, one in 10 children under one year of age will need significant hospital care if they become infected.
“This is the population that is breastfed, so knowing if there are antibodies in the milk, or for how long you will be protective after infection, or which vaccine will give your child the best protection against antibodies, is very important information, and it will be so,” said Dr. Rebecca Powell at Mount Sinai Hospital in New York, who led the research, “is relevant for a long time to come.”
The antibodies in breast milk are somewhat different from immunoglobulin G (IgG) antibodies that are prevalent in the blood and are stimulated by vaccination – although some are also excreted in breast milk. The main antibody is secretory immunoglobulin A (IgA), which sticks to the lining of children’s respiratory and intestines, helping to prevent viruses and bacteria from entering their bodies.
Although researchers have previously detected Sars-CoV-2 antibodies in breast milk, it was not clear if they could neutralize the virus, or for how long women continued to produce them after infection with the coronavirus.
To investigate, Powell and his colleagues took breast milk samples from 75 women who had recovered from Covid-19, and found that 88% contained IgA antibodies. In most cases, these were able to neutralize the SARS-CoV-2 virus, which means they can prevent infection.
Further measurements revealed that the women continued to secrete these antibodies for up to 10 months. “This means that if you continue to breastfeed, you are still giving out those antibodies in your milk,” said Powell, who presented the findings at the World Breastfeeding and Breastfeeding Symposium on September 21.
She believes that IgA antibodies extracted from breast milk could also be beneficial for adults with severe Covid-19. “It could be a great therapy, because secretory IgA is supposed to be in these mucosal areas, like the lining of the respiratory tract, and it lives and works very well there,” Powell said. “You can imagine that if it was used in a nebulizer-type treatment, it might be very effective during that window where the person got completely sick, but it hasn’t yet reached the point [being admitted to intensive care]. “
Her team also investigated the transfer of coronavirus-specific antibodies into the breast milk of 50 women after vaccination with either Pfizer, Moderna or Johnson & Johnson (J&J). All women who were injected with the Moderna vaccine, and 87% of those who received the Pfizer vaccine had IgG antibodies specific to coronavirus in their milk, while 71% and 51%, respectively, had IgA antibodies specific to the virus. For the J&J vaccine, only 38% of the women had IgG antibodies and 23% had IgA antibodies against the coronavirus in their milk.
“We know that the level of antibodies produced by RNA vaccines is very high compared to other vaccines,” Powell said. You don’t necessarily need that many antibodies to protect you from infection, but the effect of milk really depends on having a lot of antibodies in your blood that pass into your milk. Since there is a lower level stimulated by the J&J (viral vector vaccine), this is likely the reason for the very low levels in milk. “
The team is now investigating the antibody response in breast milk generated by the AstraZeneca vaccine.