Infection vs. Vaccination: Breastmilk and COVID-19 Antibodies

Since the COVID-19 vaccines have been available, many pregnant and breastfeeding parents have had some hesitation about vaccination. Some of this has been led by misinformation while some has been led by genuine and understandable concern. All expecting and new parents want to do what is best for their little one — this is what CK Public Health wants too.

One recent study should put your mind at ease about the effects of vaccination on breastmilk. Spoiler alert: results conclusively supported vaccination for breastfeeding parents.

The study was designed to look at the long-term effect of COVID-19 infection and mRNA vaccination on breast milk antibodies. This study compared breast milk antibodies from two groups of lactating parents – those with COVID-19 infection who had not been vaccinated and those who were vaccinated against COVID-19 but had not had the infection.

How was the study set up?

The group with COVID-19 infection were diagnosed by a PCR test (these are the gold standard for accurate diagnosis). There were 47 individuals in this group. Within 14 days of being diagnosed with COVID-19, the parents provided the first of six human milk samples for the study. Overall, samples were provided on days 0, 3, 7, 10, 28, and 90.

The vaccinated group contained 30 individuals who had received an mRNA vaccine (Moderna or Pfizer). They provided human milk samples before vaccination, 18 days after the first dose, and 18 and 90 days after the second dose.

When looking at the human milk samples, researchers were looking for and measuring the IgA and IgG antibodies. These are antibodies that can kill (or neutralize) the COVID-19 virus. Neither antibody is thought to be better at neutralizing the virus, but they do prompt different immune responses that can neutralize the virus.

What did we learn?

In the group of vaccinated parents, the mRNA vaccination was found to create a strong IgG response in human milk. This means that a good amount of protection against COVID-19 was provided to babies fed with breastmilk if their parent was vaccinated. The study did find that IgG levels began to decrease by 90 days after the second dose. This means booster doses of mRNA vaccines will be important for lactating parents once they are eligible for boosters.

In comparison, the antibody response in the milk of parents who were infected with COVID-19 was quite different. For this group, the initial IgA response in human milk was inconsistent – this means that while the parent was sick with COVID-19, and their infant was most at risk of contracting the virus from the parent, the protection provided through breast milk was not consistently strong as it was in vaccinated parents. However, IgA levels did show an upward or level trend past 90 days after infection.

What is our take away?

This is the first study to show that parents who contract COVID-19 as well as those who are vaccinated against COVID-19 produce breast milk that can neutralize the virus, therefore protecting breast-fed infants.

Although both vaccinated and infected parents will produce antibodies, it is important to note that the risk of severe illness or death from a COVID-19 infection is much higher than any risk from a COVID-19 vaccine. This makes vaccination for pregnant and breastfeeding individuals the best choice to protect both the parent and breastfeeding infant.

On that note, it remains important for all parents to get vaccinated, not just those who are breast feeding. Parents are in constant close contact with their children and we know that the virus spreads through close contact. Vaccination is proven to be safe and effective at reducing a person’s likelihood of getting COVID-19 and passing it to others. There are currently no COVID-19 vaccines approved for infants and children under 5 years of age in Canada. That means that the youngest members of Chatham-Kent are relying on other people’s decision to get vaccinated.

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