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

ABSTRACT

BackgroundCountries 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. MethodsUsing 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. FindingsIn a representative facility with no specific interventions, SARS-CoV-2 infection risk to a susceptible worker from contact with contaminated packaging was 2{middle dot}8 x 10-3 per 1h-period (95%CI 6{middle dot}9 x 10-6, 2{middle dot}4 x 10-2). Implementation of standard infection control measures, handwashing and masks (9{middle dot}4 x 10-6 risk per 1h-period, 95%CI 2{middle dot}3 x 10-8, 8{middle dot}1 x 10-5), substantially reduced risk (99{middle dot}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{middle dot}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{middle dot}0 x 10-6 -1{middle dot}1 x 10-5 risk per 1h-period). Decontamination of packaging in addition to these interventions reduced infection risks to below the 1{middle dot}0 x 10-6 risk threshold. InterpretationFomite-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. FundingU.S. Department of Agriculture