The Legacy of COVID-19 in Breast Milk: The Association of Elevated Anti-Inflammatory and Antimicrobial Proteins with Vaccination or Infection.

Background: Breast milk is a rich source of antimicrobial and anti-inflammatory compounds, owing to its diverse array of bioactive molecules. This study explores the presence and activity of natural antimicrobial agents in breast milk, particularly in the context of the SARS-CoV-2 pandemic.

Materials and methods: Breast milk samples were collected from 50 breastfeeding mothers, including those who had either been vaccinated against SARS-CoV-2 or had recovered from the infection. These samples were compared with a control group consisting of 10 unvaccinated mothers with no history of COVID-19. Key antimicrobial and immune-regulatory proteins-lactoferrin, lactadherin, furin, tenascin C, granzyme B, and chitinase 3-like 1-were quantified using the Luminex multiplex analyzer.

Results and discussion: All targeted biomarkers were detected in breast milk, providing insights into the immune profile transferred to infants following COVID-19 infection or vaccination. These bioactive molecules highlight breastfeeding's role in providing passive immunity and antimicrobial protection. The protein levels were found to be influenced by factors such as maternal inflammation, infant age, delivery mode, and parity, emphasizing the dynamic interaction between maternal immunity, lactation biology, and infant development.

Conclusion: Breastfeeding serves as a powerful anti-SARS-CoV-2 defense mechanism, supported by the activity of lactoferrin, lactadherin, and furin, reinforcing its critical role in child health.