Antibodies Against SARS-CoV-2 in Human Milk: Milk Conversion Rates in the Netherlands

Hannah G. Juncker, Michelle Romijn, Veerle N. Loth, Eliza J. M. Ruhé, Sjors Bakker, Saskia Kleinendorst, Christianne J. M. de Groot, Dasja Pajkrt, Aniko Korosi, Johannes B. van Goudoever*, Marit J. van Gils, Britt J. van Keulen

*Corresponding author for this work

Research output: Contribution to journalArticleAcademicpeer-review


Background: It has been demonstrated that human milk from mothers who have been infected with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) contains antibodies against the virus, which could play an important role in protecting the recipient infant against coronavirus disease 2019 (COVID-19). Seroconversion is measured frequently around the world, but the milk conversion rate is unknown. Research Aims: To determine (1) the prevalence and (2) the dynamics of immunoglobulin A (IgA) antibodies against SARS-CoV-2 in human milk amongst lactating mothers in the Netherlands. Methods: In this large prospective cohort study, lactating mothers (N = 2312) were included between October 12, 2020 and February 24, 2021. Enzyme-linked immunosorbent assay was used to determine levels of IgA antibodies in human milk and immunoglobulin G (IgG) antibodies in serum against the ectodomain of the SARS-CoV-2 spike protein. Results: A total of 691 (30.6%) participants had SARS-CoV-2 specific antibodies in human milk and/or serum. Of these participants, 524 (23.1%) had IgA antibodies against SARS-CoV-2 in human milk, and 356 (15.7%) had IgG antibodies against SARS-CoV-2 in serum. A total of 199 (8.8%) participants had antibodies in both human milk and serum. SARS-CoV-2 specific IgA antibodies in human milk remain present at least 10 months after a polymerase chain reaction confirmed infection. Conclusion: The prevalence of IgA antibodies against SARS-CoV-2 in human milk was 23.1% in our cohort. This high prevalence of antibodies in human milk might lead to passive immunity in many breastfed infants and may serve as protection against COVID-19.
Original languageEnglish
Pages (from-to)469-476
Number of pages8
JournalJournal of Human Lactation
Issue number3
Early online date2021
Publication statusPublished - Aug 2021

Cite this