Table 2 Model input parameters for evaluating the cost-effectiveness of improving ventilation in commercial spaces for the prevention of SARS-CoV-2
Parameter | Base case value | Probability distribution |
|---|---|---|
Number of people sitting in the restaurant at once | 30 | - (Changed in the sensitivity analysis from 20 to 40) |
Average age of the people sitting in the restaurant | 45 | - (Changed in the sensitivity analysis from 35 to 55) |
Probabilities and rates | ||
Probability of infection for one PFU unit exposed [based on ID50 of 280 (95% CI 130–530) PFU units] [18, 27] | 0.0024 | Beta (15.9592, 6633.707) |
Proportion of asymptomatic cases among all exposed people (excluding the ones initially asymptomatic but became symptomatic eventually) [42] | 0.25 | Beta (18.5, 55.5) |
Probability of long Covid-19 among symptomatic cases [43] | 0.133 | Beta (86.567, 564.3127) |
Infection hospitalization rate [40] | Age-dependent: 0.019 for the average age of 45 years old | Beta (98.081, 5064.077) |
Infection mortality rate [31] | Age-dependent: 0.001 for the average age of 45 years old | Beta (99.899, 99,799.1) |
Relative rate of symptomatic infection with Delta among the fully vaccinated (relative rate of 0.22 is equivalent of 78% reduction in symptomatic infection; the value represents the average effectiveness of the BNT162b2 and ChAdOx1 nCoV-19 vaccines against Delta variant) [44] | 0.22 | Beta (14.8808, 52.7592) |
Direct costs (US dollars in 2020 USD) | ||
Improving room ventilation rate to 12 ACH (by installing 5 standalone air filtration units with HEPA filters trapping ultrafine particles down to the sub-micrometer size that are uniformly installed in the room and produce an equivalence of 12 ACH for a 1000 ft2 space (each unit produces an airflow of 347 CFM and costs $750) [45] | $3750 | Gamma (100, 0.02667) |
$23,489 | Gamma (100, 0.00426) | |
Indirect costs (U.S. dollars in 2020 USD) | ||
Covid-19 infection without hospitalization for symptomatic cases (losses of productivity over 2 weeks of self-isolation) | $2800 | Gamma (100, 0.036) |
Covid-19 hospitalization (losses of productivity over 3 weeks) | $4200 | Gamma (100, 0.024) |
Premature mortality due to Covid-19 (calculating losses of annual average wage of $50,000/year beyond the age at death of 45 years old in the base case model until the age of 65 years; future values were discounted at 3%) | $793,874 | Gamma (100, 0.000126) |
Health-related quality of life | ||
Losses of QALYs associated with a Covid-19 symptomatic case [31] | 0.008 | Beta (99.192, 12,299.81) |
Losses of QALYs associated with a long Covid-19 infection [31] | 0.034 | Beta (96.566, 2743.61) |
Losses of QALYs associated with a Covid-19 hospitalization [31] | 0.020 | Beta (97.970, 4776.154) |
Losses of QALYs associated with a Covid-19 death (calculated based on an average age of 45 years at death, life expectancy of 80 years, age-dependent QALYs of the US general population, and discounting future values at 3%) [32] | 18.33 | Normal (18.33, 1.83) |