COVID-19 antibodies in breast milk fade more quickly following vaccination than after infection, a new study suggests.
Researchers from the University of Rochester School of Medicine and Dentistry in New York found that antibodies produced breastfeeding mothers whether they’ve previously been ill or have gotten their shots are both capable of neutralizing the virus.
However, lactating women who are fully vaccinated against Covid see antibodies in their milk begin to decline about 90 days after the second dose.
But new mothers who generate antibodies from previous infection see their levels either remain steady or increase three months after recovery.
The team says the findings provide evidence for why, whether previously infected or vaccinated, women should breastfeed their children to pass on protection.
Researchers from the University of Rochester School of Medicine and Dentistry in New York looked at breast milk samples from women who have been previously infected with COVID-19 or have been vaccinated (file image)
Women with prior infection had higher levels of first line of defense antibodies while vaccinated women had higher levels of antibodies that remember the virus (left). Antibody levels in the vaccinated women began declining after 90 days while the women with prior Covid illness had stable or increasing levels 90 days later (right)
For the study, published in JAMA Pediatrics, the team recruited 77 women who were currently breastfeeding.
Of the group, 47 had previously been infected with COVID-19, which was confirmed with a laboratory test.
The remaining 30 women were fully vaccinated with either the Pfizer-BioNTech or the Moderna vaccine.
Researchers tested samples of the participants’ breast milk for two types of antibodies: IgA and IgG.
IgA antibodies are typically found in mucosal areas of the body such as the nose, ears and respiratory tract and make up between 10 percent and 15 percent of all antibodies within the body.
These antibodies are the first line of defense against an infection, neutralizing viruses and preventing the pathogen from entering human cells.
Meanwhile, IgG antibodies are the smallest but most common antibody making up 75 percent to 80 percent of those within the body.
They are produced in the later stages of infection and ‘remember’ the virus so the body can mount an immune response if the virus attacks again.
Breast milk samples among the infected women were collected within 14 days of diagnosis and again at 28 days and 90 days.
The vaccinated women had samples taken pre-vaccination, 18 days after the first dose, 18 days after the second dose and again at 90 days.
Both sets of samples were found to be able to neutralize the virus at least three months later but levels are higher among the previous infection group (left)
Researchers found that breastfeeding women who previously has Covid had higher levels of IgA antibodies,
In most participants, IgG antibodies were not detected within 14 days of infection but did increase over time.
What’s more, 73 percent of participants saw a stable or upward trend of their antibody levels 90 days later.
Comparatively, breastfeeding vaccinated women had higher levels of IgA antibodies, which increased after each dose
However, levels began declining three months after the second shot.
‘Still, at 90 days after the second dose, the IgG levels were higher than those generated as a result of infection, which corroborates other non–peer-reviewed reports,’ the authors wrote.
Levels of IgA antibodies were similar to those seen among previously infected women, but declined overtime in most of the group.
However, both sets of samples were found to have neutralizing capabilities against COVID-19.
‘Both illness and vaccination resulted in human milk with neutralization activity against live wild-type SARS-CoV-2,’ they wrote.
‘Our data suggest that both IgA and IgG contribute to the neutralizing capacity, implying clinical benefit to infants receiving human milk from parents with COVID-19 infection or who are vaccinated.’