Perspective on the Potential Vertical Transmission of SARS-CoV-2 Through Breast Milk

SARS-CoV-2 is highly transmissible, having infected ~16 million children in the United States. Symptom severity is higher in infants compared to older children, possibly due to their ineligibility for vaccination. Concerns persist that mothers transmit infectious viral loads of SARS-CoV-2 through breast milk. In this review, we discuss the mechanism by which viruses transmit through breast milk, weigh the specific virulence and infectivity of SARS-COV-2, and review current guidelines for minimizing transmission in neonates.

Through available literature, we propose a stepwise pathway for vertical transmission of SARS-CoV-2. The level of risk and probability of infection is assessed based on established mechanisms, reported viral loads, and presence of transmembrane receptors.

To successfully transmit viruses through breast milk, the virus must infect the mother's breast cells, replicate in the mammary gland, be secreted into breast milk, survive contact with the infant's oral mucosa and digestive tract, infect enterocytes, replicate while evading the infant's immune system, exit the gastrointestinal tract, and enter the bloodstream for systemic infection.

We conclude that SARS-CoV-2 infection through breast milk has limited transmission risk, and benefits for infants far outweigh the risks, aligning with current AAP/WHO/CDC guidelines. Though close contact during breastfeeding and exposure to respiratory droplets pose a higher transmission risk.