Breastfeeding mothers vaccinated against coronavirus with Pfizer transmit antibodies to their children, study finds

Children breastfed by women immunized with the vaccine Pfizer could be protected against covid-19, according to a study that has concluded that breast milk contains specific antibodies against SARS-CoV-2 (IgG).

The study participants are health professionals from the Sant Joan de Déu hospital in the city of Barcelona (northeast) who carry out their work on the front line and who were concerned about the possibility of catching and transmitting the virus to their children during breastfeeding, and also due to the possible harmful effects of vaccination.

Pregnant women have been excluded from clinical trials to approve vaccines against coronavirus, although the scientific authorities consider that mRNA (messenger RNA) vaccines are safe and recommend their administration in those cases in which the possibility of contracting the disease is higher than the potential risks of vaccination, and they leave the decision to maintain breastfeeding in the hands of mothers.

In this context, and after detecting that health professionals wanted to be vaccinated without abandoning breastfeeding, the Sant Joan de Déu Health Park promoted the study LacCOVID, published in medRixv.

“The results encourage all lactating women who are breastfeeding to be vaccinated with mRNA-based vaccines without interrupting breastfeeding,” said Erika Esteve and Vicens Díaz de Brito, associate physician and head of the Infectious Diseases Service of the Hospital de Sant Boi (Barcelona) of the Sant Joan de Déu Sanitary Park, respectively, both coordinators of this work.

The study demonstrates the existence of specific antibodies against SARS-CoV-2 (IgG) in milk and blood of lactating women who have been vaccinated with Pfizer-BioNTech.

The study began in February at the hands of Erika Esteve, a doctor and nursing mother of a baby born in 2020, who wanted to be vaccinated and found that there was a gap in information about vaccination in breastfeeding mothers, which led her to undertake the investigation.

She is one of 32 professionals at the center participating in the study and the results of the first 18 women who have completed the follow-up have now been published.

All are or have been in the first line, their mean age is 37.8 years and the mean postpartum time is 18.7 months.

To carry out the study, they have extracted 52 samples of breast milk and blood, which they have analyzed at three different times: after receiving the first dose of the vaccine, two weeks after this and four weeks after the second dose.

Thus, they have seen that antibodies against coronavirus increase notably after the second dose and that the levels of IgG (antibodies) in the blood are correlated with the levels in breast milk, a fact that would allow an approximate calculation of the levels of vaccine IgG in breast milk in the future, only with a blood test from the mother.

The serological tests showed that none of the participants had previously suffered the Covid-19 They also did not contract it during the study, when the antigen test was also performed prior to each sampling.

The study continues until the 32 participating women have been followed up.