High rates of oxidative stress are common in preterm born infants and have short- and long-term consequences. The antioxidant properties of human milk limits the consequences of excessive oxidative damage. However, as the mother’s own milk it is not always available, donor milk may be provided as the best alternative. Donor milk needs to be pasteurized before use to ensure safety. Although pasteurization is necessary for safety reasons, it may affect the activity and concentration of several biological factors, including antioxidants. This literature review describes the effect of different pasteurization methods on antioxidant properties of human milk and aims to provide evidence to guide donor milk banks in choosing the best pasteurization method from an antioxidant perspective. The current literature suggests that Holder pasteurization reduces the antioxidant properties of human milk. Alternative pasteurization methods seem promising as less reduction is observed in several studies.

SARS-CoV-2-specific antibodies are secreted into human milk of infected or vaccinated lactating women and might provide protection to the breastfed infant against COVID-19. Differences in antibody response after these types of exposure are unknown. In this longitudinal cohort study, we compared the antibody response in human milk following SARS-CoV-2 vaccination or infection. We analyzed 448 human milk samples of 28 lactating women vaccinated with the SARS-CoV-2 vaccine BNT162b2 as well as 82 human milk samples of 18 lactating women with a prior SARS-CoV-2 infection. The levels of SARS-CoV-2-specific IgA in human milk were determined over a period of 70 days both after vaccination and infection. The amount of SARS-CoV-2-specific IgA in human milk was similar after SARS-CoV-2 vaccination and infection. After infection, the variability in IgA levels was higher than after vaccination. Two participants with detectable IgA prior to vaccination were analyzed separately and showed higher IgA levels following vaccination compared to both groups. In conclusion, breastfed infants of mothers who have been vaccinated with the BNT162b2 vaccine receive human milk with similar amounts of SARS-CoV-2-specific antibodies compared to infants of previously infected mothers.

Moderate exercise results in a significant increase in serum and salivary immunoglobulins. Maternal physical activity might therefore also be a factor influencing antibody levels in human milk. This study aims to determine the influence of physical activity on SARS-CoV-2-specific Immunoglobulin A (IgA) in human milk and Immunoglobulin G (IgG) in serum. In this prospective cross-sectional cohort study, all lactating women in the Netherlands were eligible to participate. SARS-CoV-2-specific IgA in human milk and IgG in serum were determined using an enzyme-linked immunosorbent assay (ELISA). Data on performed physical activity was collected using the Short Questionnaire to Assess Health enhancing physical activity (SQUASH), which includes intensity and duration of the performed activity. In total, 356 out of 2312 lactating women tested positive for SARS-CoV-2-specific antibodies in serum. Of them, 323 filled in the questionnaire and were included in the analysis. An association between the activity score and SARS-CoV-2-specific antibodies in human milk (B = 1·035, 95·0% CI = 1·019 to 1·052, p = 0·042) and serum (B = 1·019, 95·0% CI = 1·009 to 1·029, p = 0·048) was demonstrated. No association was found between the duration of physical activity and SARS-CoV-2-specific antibodies in human milk or serum. Our findings suggest that physical activity is beneficial for the levels of SARS-CoV-2-specific antibodies in human milk and serum, with the intensity of the physical activity being the most important contributor to this relationship. A higher level of antibodies in human milk might provide better immunological protection for infants against COVID-19.

Newborns are born with an immature immune system, making them susceptible to infections early in life. Human milk provides essential nutrients and immunological factors that support infant immunity. Maternal vaccination during lactation has the potential to enhance these benefits by triggering an immune response in the mother, potentially extending protection to her child. However, lactating individuals are often excluded from vaccine trials, leading to uncertainties about vaccine safety and efficacy during the postpartum period. This study critically evaluates the effectiveness of vaccines in enhancing the immune-supporting properties of human milk and assesses their safety and efficacy for lactating mothers and their infants. By examining potential benefits alongside safety concerns, we aim to provide a comprehensive understanding of postpartum vaccination’s impact on maternal and infant health. We utilized large-language models (LLMs) to enhance the review process and performed a structured literature search across Ovid/Medline, Embase, and Clarivate Analytics using terms like “breastfeeding”, “postpartum”, and “vaccination”. A three-stage screening process involving human and LLM-assisted evaluation focused on postpartum vaccines and their implications for maternal and infant health. We identified 73 studies covering vaccines against COVID-19, cholera, influenza, pertussis, pneumococcal, rabies, polio, rotavirus, rubella, varicella, typhoid, smallpox, and yellow fever. Most vaccines, such as those for COVID-19 and influenza, appear safe and effective for postpartum use without requiring precautionary measures. However, caution is advised with vaccines such as the yellow fever vaccine, where temporary breastfeeding cessation is recommended. Overall, this review underscores the compatibility of most vaccines with lactation and suggests its benefits for both mother and infant.