Low risk of SARS-CoV-2 transmission via fomite, even in cold-chain

Sobolik, Julia S.; Sajewski, Elizabeth T.; Jaykus, Lee-Ann; Cooper, D. Kane; Lopman, Ben A.; Kraay, Alicia NM.; Ryan, P. Barry; Guest, Jodie L.; Webb-Girard, Amy; Leon, Juan S.

BACKGROUND: Countries continue to debate the need for decontamination of cold-chain food packaging to reduce possible SARS-CoV-2 fomite transmission among workers. While laboratory-based studies demonstrate persistence of SARS-CoV-2 on surfaces, the likelihood of fomite-mediated transmission under real-life conditions is uncertain. METHODS: Using a quantitative risk assessment model, we simulated in a frozen food packaging facility 1) SARS-CoV-2 fomite-mediated infection risks following worker exposure to contaminated plastic packaging; and 2) reductions in these risks attributed to masking, handwashing, and vaccination. FINDINGS: In a representative facility with no specific interventions, SARS-CoV-2 infection risk to a susceptible worker from contact with contaminated packaging was 2·8 x 10(−3) per 1h-period (95%CI: 6·9 x 10(−6), 2·4 x 10(−2)). Implementation of standard infection control measures, handwashing and masks (9·4 x 10(−6) risk per 1h-period, 95%CI: 2·3 x 10(−8), 8·1 x 10(−5)), substantially reduced risk (99·7%). Vaccination of the susceptible worker (two doses Pfizer/Moderna, vaccine effectiveness: 86-99%) combined with handwashing and masking reduced risk to less than 1·0 x 10(−6). Simulating increased infectiousness/transmissibility of new variants (2-, 10-fold viral shedding) among a fully vaccinated workforce, handwashing and masks continued to mitigate risk (2·0 x 10(−6)-1·1 x 10(−5) risk per 1h-period). Decontamination of packaging in addition to these interventions reduced infection risks to below the 1·0 x 10(−6) risk threshold. INTERPRETATION: Fomite-mediated SARS-CoV-2 infection risks were very low under cold-chain conditions. Handwashing and masking provide significant protection to workers, especially when paired with vaccination. FUNDING: U.S. Department of Agriculture