Objective Synthesise evidence on production of SARS-CoV-2 antibodies in human milk of individuals who had COVID-19, and antibodies’ ability to neutralise SARS-CoV-2 infectivity.
Design A systematic review of studies published from 1 December 2019 to 16 February 2021 without study design restrictions.
Setting Data were sourced from PubMed, MEDLINE, Embase, CNKI, CINAHL and WHO COVID-19 database. Search was also performed through reviewing references of selected articles, Google Scholar and preprint servers. Studies that tested human milk for antibodies to SARS-CoV-2 were included.
Patients Individuals with COVID-19 infection and human milk tested for anti-SARS-CoV-2 neutralising antibodies.
Main outcome measures The presence of neutralising antibodies in milk samples provided by individuals with COVID-19 infection.
Results Individual participant data from 161 persons (14 studies) were extracted and re-pooled. Milk from 133 (82.6%) individuals demonstrated the presence of anti-SARS-CoV-2 immunoglobulin A (IgA), IgM and/or IgG. Illness severity data were available in 146 individuals; 5 (3.4%) had severe disease, 128 (87.7%) had mild disease, while 13 (8.9%) were asymptomatic. Presence of neutralising antibodies in milk from 20 (41.7%) of 48 individuals neutralised SARS-CoV-2 infectivity in vitro. Neutralising capacity of antibodies was lost after Holder pasteurisation but preserved after high-pressure pasteurisation.
Conclusion Human milk of lactating individuals after COVID-19 infection contains anti-SARS-CoV-2-specific IgG, IgM and/or IgA, even after mild or asymptomatic infection. Current evidence demonstrates that these antibodies can neutralise SARS-CoV-2 virus in vitro. Holder pasteurisation deactivates SARS-CoV-2-specific IgA, while high-pressure pasteurisation preserves the SARS-CoV-2-specific IgA function.
Data availability statement
All data relevant to the study are included in the article or uploaded as supplemental information. The data were extracted from the published literature. The details of all such literature used are included in the manuscript.
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Contributors JML and YWL designed, analysed and interpreted the data. CYCL, MC and NBHN drafted the work and contributed to the design and conception of the study. JML, ZA, YPN and YZ analysed and revised the manuscript critically for important intellectual content.
Funding The authors have not declared a specific grant for this research from any funding agency in the public, commercial or not-for-profit sectors.
Competing interests None declared.
Provenance and peer review Not commissioned; externally peer reviewed.
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