Breastfeeding after the COVID-19 vaccination is safe and minimally changes milk composition

Breastfeeding after the COVID-19 vaccination is safe and minimally changes milk composition

Cutting-edge research shows that SARS-CoV-2 infection disrupts milk composition, but vaccines ensure the safety of breastfeeding mothers and their babies.

In a recent study published inThe Journal of NutritionA group of researchers investigated whether severe infection with acute respiratory syndrome coronavirus 2 (SARS-CoV-2) or vaccination against coronavirus disease 2019 (COVID-19) causes compositional changes in breast milk, including the presence of vaccine components.

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Comprehensive lipidomic and metabolomic results: SARS-CoV-2 infection was associated with significant changes in 385 lipid species and 13 metabolites, highlighting changes such as reduced anti-inflammatory fatty acid esters and increased pro-inflammatory ceramides.

Breast milk is the gold standard for infant nutrition, providing essential nutrients, immune cells and immunomodulatory components that protect infants with immature immune systems. While it reduces infections, it can transmit certain pathogens such as human immunodeficiency virus (HIV) and Ebola virus.

Initial concerns about transmission of SARS-CoV-2 through breast milk led to disruption in breastfeeding practices, although subsequent evidence emerged that no transmission occurred and that there were significant immune responses in milk following infection. However, there is limited data on how SARS-CoV-2 infection and COVID-19 vaccination affect milk composition.

Further research is needed to fully understand these impacts, particularly through multi-omics approaches to establish evidence-based guidelines for breastfeeding mothers during pandemics.

About the study

Participants in this study were breastfeeding individuals aged 18 years or older who either tested positive for SARS-CoV-2 or had received a COVID-19 vaccine. Milk samples from vaccinated participants were included if they had no history of SARS-CoV-2 infection and were scheduled for vaccination with the Pfizer, Moderna, or Johnson and Johnson (J&J) vaccines.

Milk was self-collected in clean containers at specified intervals before and after vaccination, with collection procedures approved by the Mount Sinai Hospital Institutional Review Board (IRB). For participants with SARS-CoV-2 infection, milk samples were collected within seven days of a confirmed positive test, with collection procedures approved by the University of Idaho IRB.

Milk samples were frozen immediately after collection, stored at -80°C, and analyzed using multi-omics approaches to examine proteins, metabolites, and lipids. The analysis used advanced statistical methods such as repeated measures analysis of variance (rANOVA) and pathway enrichment analysis to identify significant changes in milk composition.

Protein, metabolite and lipid extraction (MPLEx) techniques have been used to inactivate pathogens and isolate biomolecules. For proteomic analysis, proteins were digested and labeled using isobaric tandem mass tag (TMT), while lipids and metabolites were analyzed using liquid chromatography-mass spectrometry (LC-MS/MS).

Study results

Presence of vitamin C and paracetamol: In addition to paracetamol, elevated levels of ascorbic acid and its derivative threonic acid were detected in the milk of SARS-CoV-2-infected participants, suggesting possible maternal dietary or drug reactions to the disease.

Study participants were between 26 and 41 years old, with a mean age of 32 years, and were between less than one month and 30 months postpartum, with a mean of 8 months postpartum.

Milk samples were analyzed after extraction with the MPLEx method using multi-omics approaches including proteomics, metabolomics and lipidomics. Significant changes in the composition of milk proteins, metabolites and lipids were identified in association with SARS-CoV-2 infection and compared to baseline control values. However, for the COVID-19 vaccination, the samples were compared to the pre-vaccination milk of the same participants because no pre-infection samples were available for those with SARS-CoV-2 infection.

SARS-CoV-2 infection was associated with significant changes in 67 milk proteins within seven days of infection. These changes included 43 proteins with increased expression and 24 with decreased expression, mainly related to systemic inflammatory pathways. Specific pathways included NOD-like receptor signaling, JAK-STAT signaling, and responses to hepatitis C and influenza infections. Changes were also noted in lipid composition, with 385 lipid molecule species showing differences.

Pro-inflammatory lipids such as ceramides were increased, while anti-inflammatory lipids such as fatty acid esters of hydroxyl fatty acids were reduced. Metabolic analysis revealed 13 significantly altered metabolites, including ascorbic acid and its derivatives and the anti-inflammatory drug paracetamol.

In contrast, COVID-19 vaccination resulted in minimal changes in milk composition. No significant changes in milk lipidomics or metabolomics were observed for any of the vaccine types examined. Proteomic changes varied by vaccine and time point.

No vaccine components in milk: Despite sensitive mass spectrometry techniques, no synthetic lipids, mRNA or adenoviral proteins from vaccines were detected in milk samples, providing solid evidence of the safety of the vaccine for nursing mothers.

The Moderna vaccine resulted in changes in eight proteins 1-6 hours after vaccination, while the J&J vaccine only showed one protein change over the same period. On day three, the J&J vaccine showed changes in 13 proteins, compared to two and four proteins for Moderna and Pfizer, respectively.

The J&J vaccine uniquely activated pathways such as NF-kappa-B signaling and RIG-I-like receptor signaling, reflecting its design as an adenovirus-vectored vaccine. Proteomic pathway analysis revealed an overlap between the J&J vaccine and SARS-CoV-2 infection, primarily affecting systemic inflammatory pathways, but changes caused by the vaccine were less extensive than those caused by infection.

Studies on the presence of vaccine components in milk found that no synthetic lipids or adenoviral proteins were detectable in any of the samples, suggesting that vaccine components do not pass into breast milk.

Conclusions

In summary, there is global consensus that the risk of contracting COVID-19 through breast milk feeding is negligible, while the benefits of breastfeeding during and after infection or vaccination are significant. The effects of vaccination on breastfeeding individuals are small, and there is no evidence of harm to infants consuming milk from vaccinated mothers. Although traces of the vaccine messenger ribonucleic acid (mRNA) have been detected in some milk samples, its physiological significance is unclear.

This study demonstrated significant changes in milk composition following SARS-CoV-2 infection, including >65 altered proteins, 395 lipids, and 13 metabolites. In comparison, vaccine-related changes in ≤13 proteins were predominantly transient and vaccine-specific, with no changes in lipids or metabolites. No vaccine components were detected in milk, underlining the safety of the vaccine for breastfeeding individuals.

These results highlight the importance of vaccination in protecting breastfeeding individuals and their infants during pandemics.

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