Relationship between anti-SARS-CoV-2-specific antibodies in human breast milk following SARS-CoV-2 infection during pregnancy: a prospective cohort study

Abstract

Objective: To determine the presence of anti-SARS-CoV-2 antibodies in colostrum and mature milk in women who had SARS-CoV-2 infection during pregnancy or at delivery; to investigate the correlation between anti-SARS-CoV-2 antibodies in milk with antibody in maternal blood, severity of infection and time-interval from active illness; and to evaluate immunoglobulin evolution from colostrum to mature milk. Design: prospective cohort-study Setting: six hospitals in Spain and Hong-Kong. Sample: pregnant women with confirmed SARS-CoV-2 infection during pregnancy or at delivery. Methods: Colostrum and mature milk were collected by manual expression with strict contact precautions. Colostrum samples were tested with rRT-PCR-SARS-CoV-2 and both, maternal milk and serum were tested against SARS-CoV-2 specific immunoglobulin M, A and G reactive to receptor binding domain of SARS-CoV-2 spike protein-1. Results: All rRT-PCR-SARS-CoV-2 tested negative. IgA and IgG were present in 111/135 (82.2%) and 2/135 (1.5%) colostrum samples and 27/81 (33.3%) and 0/81 mature milk samples, respectively. Concentrations of immunoglobulins were not associated with the timing of infection but women with SARS-CoV-2 pneumonia had higher levels of IgA and IgG in colostrum than those who were asymptomatic or had mild symptoms. Conclusion: No SARS-CoV-2 virus was found in human milk, however, high levels of antibodies were found in colostrum, specially IgA, irrespective of the time of infection. All women should be encouraged to breastfeed, undertaking strict contact precautions when there is active disease. Funding: Spanish Government grant (Instituto de Salud Carlos III: COV20/00188). Synlab Diagnostics’ Globales (Madrid, Spain). Perkin Elmer.