No abstract

Countries continue to debate the need for decontamination of cold-chain food packaging to reduce possible severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) fomite transmission among frontline 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. Using a quantitative microbial risk assessment model of a frozen food packaging facility, we simulated 1) SARS-CoV-2 fomite-mediated infection risks following worker exposure to contaminated plastic packaging; and 2) reductions in these risks from masking, handwashing, and vaccination. In a frozen food facility without interventions, SARS-CoV-2 infection risk to a susceptible worker from contact with contaminated packaging was 1.5 × 10 −3 per 1h-period (5th – 95th percentile: 9.2 × 10 −6 , 1.2 × 10 −2 ). Standard food industry infection control interventions, handwashing and masking, reduced risk (99.4%) to 8.5 × 10 −6 risk per 1h-period (5th – 95th percentile: 2.8 × 10 −8 , 6.6 × 10 −5 ). Vaccination of the susceptible worker (two doses Pfizer/Moderna, vaccine effectiveness: 86–99%) with handwashing and masking reduced risk to 5.2 × 10 −7 risk per 1h-period (5th – 95th percentile: 1.8 × 10 −9 , 5.4 × 10 −6 ). Simulating increased transmissibility of current and future variants (Delta, Omicron), (2-, 10-fold viral shedding) among a fully vaccinated workforce, handwashing and masking continued to mitigate risk (1.4 × 10 −6 - 8.8 × 10 −6 risk per 1h-period). Additional decontamination of frozen food plastic packaging reduced infection risks to 1.2 × 10 −8 risk per 1h-period (5th – 95th percentile: 1.9 × 10 −11 , 9.5 × 10 −8 ). Given that standard infection control interventions reduced risks well below 1 × 10 −4 (World Health Organization water quality risk thresholds), additional packaging decontamination suggest no marginal benefit in risk reduction. Consequences of this decontamination may include increased chemical exposures to workers, food quality and hazard risks to consumers, and unnecessary added costs to governments and the global food industry.

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.

Essential food workers experience an elevated risk of SARS-CoV-2 infection due to prolonged occupational exposures (e.g., frequent close contact, enclosed spaces) in food production and processing areas, shared transportation (car or bus), and employer-provided shared housing. The purpose of this study was to evaluate the impact of combined food industry interventions and vaccination on reducing the daily cumulative risk of SARS-CoV-2 infection for produce workers. Six linked quantitative microbial risk assessment models were developed in R to simulate daily scenarios experienced by a worker. Standard industry interventions (2 m physical distancing, handwashing, surface disinfection, universal masking, increased ventilation) and two-dose mRNA vaccinations (86-99% efficacy) were modeled individually and jointly to assess risk reductions. The infection risk for an indoor (0.802, 95% Uncertainty Interval [UI]: 0.472-0.984) and outdoor (0.483, 95% UI: 0.255-0.821) worker reduced to 0.018 (93% reduction) and 0.060 (87.5% reduction), respectively, after implementation of combined industry interventions. Upon integration with vaccination, the infection risk for indoor (0.001, 95% UI: 0.0001-0.005) and outdoor (0.004, 95% UI: 0.001-0.016) workers was reduced by >99.1%. Food workers face considerable risk of occupationally-acquired SARS-CoV-2 infection without intervention; however, consistent implementation of key infection control measures paired with vaccination effectively mitigates these risks.

The SARS-CoV-2 global pandemic poses significant health risks to workers who are essential to maintaining the food supply chain. Using a quantitative risk assessment model, this study characterized the impact of risk reduction strategies for controlling SARS-CoV-2 transmission (droplet, aerosol, fomite-mediated) among front-line workers in a representative enclosed food manufacturing facility. We simulated: 1) individual and cumulative SARS-CoV-2 infection risks from close contact (droplet and aerosols at 1-3m), aerosol, and fomite-mediated exposures to a susceptible worker following exposure to an infected worker during an 8h-shift; and 2) the relative reduction in SARS-CoV-2 infection risk attributed to infection control interventions (physical distancing, mask use, ventilation, surface disinfection, hand hygiene). Without mitigation measures, the SARS-CoV-2 infection risk was largest for close contact (droplet and aerosol) at 1m (0.96, 95%CI: 0.67-1.0). In comparison, risk associated with fomite (0.26, 95%CI: 0.10-0.56) or aerosol exposure alone (0.05, 95%CI: 0.01-0.13) at 1m distance was substantially lower (73-95%). At 1m, droplet transmission predominated over aerosol and fomite-mediated transmission, however, this changed by 3m, with aerosols comprising the majority of the exposure dose. Increasing physical distancing reduced risk by 84% (1 to 2m) and 91% (1 to 3m). Universal mask use reduced infection risk by 52-88%, depending on mask type. Increasing ventilation (from 0.1 to 2-8 air changes/hour) resulted in risk reductions of 14-54% (1m) and 55-85% (2m). Combining these strategies, together with handwashing and surface disinfection, resulted in <1% infection risk. Current industry SARS-CoV-2 risk reduction strategies, particularly when bundled, provide significant protection to essential food workers.