SARS-CoV-2 in human milk is inactivated by Holder pasteurization but not cold storage

Walker, G. J.; Clifford, V.; Bansal, N.; Ospina Stella, A.; Turville, S.; Stelzer-Braid, S.; Klein, L. D.; Rawlinson, W.

As the COVID-19 pandemic evolves, human milk banks worldwide continue to provide donor human milk to vulnerable infants who lack access to mothers own milk. Under these circumstances, ensuring the safety of donor human milk is paramount, as the risk of vertical transmission of SARS-CoV-2 is not well understood. Here, we investigate the inactivation of SARS-CoV-2 in human milk by pasteurisation, and the stability of SARS-CoV-2 in human milk under cold storage (freezing or refrigeration). Following heating to 63{degrees}C or 56{degrees}C for 30 minutes, SARS-CoV-2 replication competent (i.e. live) virus was undetected in both human milk and the control medium. Cold storage of SARS-CoV-2 in human milk (either at 4{degrees}C or -30{degrees}C) did not significantly impact infectious viral load over a 48 hour period. Our findings demonstrate that SARS-CoV-2 can be effectively inactivated by Holder pasteurisation, and confirm that existing milk bank processes will effectively mitigate the risk of transmission of SARS-COV-2 to vulnerable infants through pasteurised donor human milk.