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.

But, after receiving the second dose of vaccine against Covid antibodies, milk antibody levels in lactating moms begin to decrease around 90 days.

New mothers that have developed antibodies after an infection previously seen their levels rise or stay the same for three months.

According to the team, these findings show that women, regardless of whether they have been previously infected, should continue to breastfeed their babies for 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)

New York University School of Medicine and Dentistry examined breast milk samples of women infected or vaccinated against COVID-19.

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)

Pre-infected women were more likely to have high levels of their first line defense antibodies, while those who had been vaccinated had lower levels. The antibody levels of vaccinated women started to decline after 90 days, while those with previous Covid disease had steady or increased levels for 90 days (right).

The study was published in JAMA Pediatrics. It involved 77 breastfeeding women.

The laboratory tests confirmed that 47 of the participants had been previously infected by COVID-19.

Rest of the 30 women had been fully vaccinated either with the Moderna vaccination or Pfizer BioNTech.

Two types of antibodies were tested on breast milk samples taken from the participants by researchers: IgA, and IgG.

IgA antibodies, which are found in the mucosal area of the body like the nose and ears as well as the respiratory tract, make up about 10 percent to 15 percent of all antibodies.

These antibodies act as a first line of defense to an infection.

IgG antibodies make up approximately 75 to 80 percent of all the body’s antibody levels.

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.

The breast milk samples of infected women were obtained within 14 days. They could also be collected at 28 or 90 days.

Pre-vaccination samples were taken by the women who had been vaccinated. They were collected 18 days before, 18 day after, and 90 days afterwards.

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)

Each set of samples was able to kill the virus within three months, but the levels in the former infection group (left), are much higher.

Research showed that women breastfeeding after having Covid were more likely to have IgA antibodies.

In most participants, IgG antibodies were not detected within 14 days  of infection but did increase over time.

Additionally, the majority of participants experienced a stabilizing or increasing trend in antibody levels after 90 days. 

Contrary to the previous results, breastfeeding vaccinated mothers had higher IgA antibody levels, which increased with each dose.  

The levels dropped three months later.

‘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.

The levels of IgA antibodies in the patients were comparable to that in previously infected women but decreased over time in many of them.

Both sets of samples had neutralizing abilities against COVID-19.    

Their conclusion was that both illness and vaccination had resulted in human breast milk with neutralization activity for live SARS-CoV-2.

“Our data indicate that IgA, and IgG are both important in neutralizing the immune system. This could have a positive clinical effect on infants who drink human milk of parents with COVID-19 or who have been vaccinated.