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The mRNA COVID-19 vaccines produced better antibody response in human milk from lactating women compared with the adenovirus vector-based vaccines, results from a Dutch study suggested.
Almost all lactating women who received either the Pfizer-BioNTech (96%) or Moderna (97%) mRNA vaccines had detectable IgA antibodies in their milk, reported Hannah Juncker, MD, of Emma Children’s Hospital in Amsterdam, and colleagues.
In contrast, only 39% of lactating women who got the AstraZeneca vaccine and 48% of those who got the Johnson & Johnson vaccine had detectable IgA levels in their milk, they noted in a research letter in JAMA Pediatrics.
“Based on these data, we suggest that an mRNA-based vaccine is the optimal choice for lactating women when they want to transfer antibodies to their infants,” the authors wrote.
Participants who received both doses of the Pfizer-BioNTech, Moderna, and AstraZeneca vaccines all had detectable IgG antibody levels, which were found at day 23 after the first dose for Pfizer-BioNTech recipients and at day 32 for Moderna recipients compared with day 94 for AstraZeneca recipients, “which can be explained by timing of the second dose,” the researchers said.
For the one-dose Johnson & Johnson vaccine, only 28% of participants had detectable IgG levels in their milk.
IgA and IgG antibodies are both found in breast milk, but IgA makes up 90% of the antibodies found in human milk. As babies are born with low levels of IgA antibodies, those from their mothers’ milk are important until they can produce their own antibodies.
“Although, to our knowledge, no studies have shown indisputable evidence that human-milk IgA directly protects against respiratory tract infections, it is very likely that this antibody plays a critical role,” Juncker and colleagues wrote.
Previous studies have also shown that SARS-CoV-2 antibodies can be found in breast milk of lactating mothers after vaccination and after COVID-19 infection. Studies also suggest breast milk is not a likely source of COVID-19 transmission.
This prospective longitudinal study was conducted from January to July 2021 in the Netherlands, where four COVID-19 vaccines are available. Lactating women who received full vaccination from any one of the four vaccines were eligible to participate in the study, though those with a prior positive PCR test or detectable SARS-CoV-2 antibodies at baseline were excluded.
Each participant collected 17 milk samples over 100 days, and in total, 1,650 milk samples from 124 lactating mothers were included. Milk samples were then tested with an enzyme-linked immunosorbent assay with the SARS-CoV-2 spike protein to detect IgA and IgG antibodies.
The researchers noted that they did not measure the neutralizing capacity of the human milk antibodies, which was a limitation to the study.
Créditos: Comité científico Covid