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Background Since the outbreak of COVID-19, many put their hopes in the rapid development of effective immunizations. For now patient isolation, physical distancing and good hygiene are the sole measures for prevention. Processed breast milk with antibodies against SaRS-CoV-2 may serve as additional protection. We aimed to determine the presence and neutralization capacity of antibodies against SaRS-CoV-2 in breastmilk of mothers who have recovered from COVID-19. Methods This prospective case control study included lactating mothers, recovered from (suspected) COVID-19 and healthy controls. Serum and breastmilk was collected. To assess the presence of antibodies in breastmilk and serum, we used multiple complementary assays, namely ELISA with the SARS-CoV-2 spike protein, SARS-CoV-2 receptor binding domain (RBD) and with the SARS-CoV-2 nucleocapsid (N) protein for IgG and bridging ELISA with the SARS-CoV-2 RBD and N protein for total Ig. To assess the effect of pasteurization breastmilk was exposed to Holder Pasteurization and High Pressure Pasteurization. Results Breastmilk contained antibodies against SARS-CoV-2 using any of the assays in 24 out of 29 (83%) proven cases, in six out of nine (67%) suspected cases and in none of the 13 controls. In vitro neutralization of SARS-CoV-2 clinical isolate virus strain was successful in a subset of serum (13%) and milk samples (26%). Although after pasteurization of the milk SARS-CoV-2 antibodies were detected with both methods of pasteurization, virus neutralizing capacity of those antibodies was only retained with the HPP approach. Conclusion Breastmilk of mothers who recovered from COVID-19 contains significant amounts of IgA against SARS-CoV-2, both before and after pasteurization. Key Points Question Does breastmilk of mothers who have recovered from coronavirus disease 2019 (COVID-19) contain antibodies against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2)? Findings We provide multiple lines of evidence on the presence of a variety of antibodies against SARS-CoV-2, with no such antibodies present in the controls. These antibodies are capable of neutralizing a clinical isolate of SARS-CoV-2 in vitro. We furthermore show that high pressure pasteurization hardly affects antibody levels and efficacy. Meaning Breastmilk, obtained from mothers who have recovered from COVID-19, may serve as a safe and widely applicable preventive strategy for vulnerable high risk populations

Objective: When own mother's milk falls short, pasteurized human donor milk is recommended as alternative feeding for preterm infants. Donor milk has to meet the highest safety standards, but its processing and storage is expensive. The recommended storage time of pasteurized donor milk is 3 months. The objective of the present study was to determine whether the frozen storage time of pasteurized donor milk can be extended beyond 3 months without compromising its safety and quality. Methods: For this prospective observational study breast milk samples of 34 unique women, collected between November 2014 and June 2015, were provided by the Dutch Human Milk Bank. Samples were Holder pasteurized within 3 months after expression and stored at -20°C. Analysis of both bacterial growth (by inoculation of milk on a blood and a cysteine-, lactose-, and electrolyte-deficient agar) and fat, crude protein, carbohydrate and energy content of milk (analyzed by infrared spectroscopy) was done monthly during the first 6 months and every 2 months thereafter, up to 1 year postpasteurization. Results: Thirty of 306 (9.8%) follow-up samples showed bacterial growth when cultured. None of the samples showed sequential contamination with the same strain up to 8 months of frozen storage. No significant decreases in macronutrients and energy content were observed over 8 months. Conclusion: Pasteurized human donor milk can be stored safely for 8 months at -20°C, without compromising its macronutrient and energy content. This longer storage time will reduce disposal of expired donor milk and subsequently reduce costs.