Detection of SARS-CoV-2 RNA and antibodies in breast milk of infected mothers

The SARS-CoV-2 outbreak in December 2019 brought many challenges to be addressed. One concerns the possible transmission of the virus and protective antibodies against SARS-CoV-2 to newborns through breastfeeding. The aim of this study was the detection of SARS-CoV-2 RNA and antibodies in the milk of SARS-CoV-2 positive mothers. Milk and blood samples were collected from twelve women with SARS-CoV-2 positive nasopharyngeal swabs. Viral RNA was investigated by RT-PCR, and the presence of IgA, IgM, and IgG anti-SARS-CoV-2 was evaluated in both breast milk and maternal blood. All milk samples showed negative results for SARS-CoV-2 RNA. Eight women (66%) had a detectable level of anti -SARS-CoV-2 IgA in their milk. Of this group, only one sample presented simultaneously serum antiviral IgM and IgG while other three samples showed only anti-SARS-CoV-2 IgG. The remaining four mothers with anti-SARS-CoV-2 IgA in their breast milk had no serum antibodies against SARS-CoV-2. Finally, four mothers (34%) did not have any anti-SARS-CoV-2 antibodies in breast milk and serum, except one mother who had antiviral IgG and IgA in serum. Our results suggest that breastfeeding of SARS-CoV-2 infected mothers is safe and should be encouraged as breast milk transmits maternal antiviral antibodies which protect the infant while its immune system is immature.