Model parameters for SARS-CoV-2 transmission
| Parameter | Mean (95% CI) | Model | Source and notes |
|---|---|---|---|
| Incubation period, d | 5.08 (4.77–5.39) | Sampled | He et al.; (10) meta-analysis estimate of the mean incubation time |
| Latent period, d | 2.50 | Fixed | Tuite et al.; (11) retrospective cohort study estimate of the mean time to exposure to onset of infectiousness |
| Time to isolation | |||
| Symptom-based, d | 4.60 (4.10–5.00) | Sampled | Bi et al.; (12) retrospective cohort study estimate of the mean time to isolation |
| Contact-based, d | 1.90 (1.10–2.70) | Sampled | |
| Recovery time, d | 20.80 (20.10–21.50) | Sampled | Bi et al.; (12) retrospective cohort study estimate of the mean recovery time |
| Asymptomatic infection rate, % | 46.00 (18.40–73.60) | Sampled | He et al.; (10) Meta-analysis estimate of the mean asymptomatic infection rate (10) |
| Attack rate, % | 6.10 (3.00–12.10) | Sampled | Koh et al.; (13) retrospective cohort study estimate of the mean attack rate. We used the estimate for 20–29 years of age. |
| Secondary attack rate, % | 4.00 (2.80–5.20) | Fixed | Koh et al.; (13) meta-analysis estimate of the mean secondary attack rate (SAR). We used the nonhousehold SAR and the ratio of symptomatic versus asymptomatic SAR to calculate the probability of virus spread for symptomatic and nonsymptomatic contacts, respectively. |
| Outside transmission, cases/100 000/wk | 153 | Fixed | We performed the calculation of the probability of outside transmission on a daily basis based on the incident rate reported by the Government of Alberta; (14) population statistics were taken from Statistics Canada. (15) |
| Test duration, d | 2 | Fixed | Government of Alberta; (14) less than 2 days from swab collection to test result (1 d for the laboratory to receive the swab and 13 h for the result) |
| Isolation period, d | 14 | Fixed | Government of Alberta (16) mandatory isolation guideline |
| Vaccine effectiveness (1 dose), % | 30.70 (25.20–35.70) | Fixed (mean) | Lopez Bernal et al. (17) Effectiveness of BNT162b2 (Pfizer-BioNTech) and ChAdOx1 nCoV-19 (AstraZeneca) vaccination against symptomatic disease caused by the B.1.617.2 (delta) variant. |
| Vaccine effectiveness (2 doses), % | 79.60 (76.70–82.10) | Fixed (mean) | Lopez Bernal et al. (17) Effectiveness of BNT162b2 (Pfizer-BioNTech) and ChAdOx1 nCoV-19 (AstraZeneca) vaccination against symptomatic disease caused by the B.1.617.2 (Delta) variant. |
| Initial seeding | 1 student | Fixed | We assumed an initial outbreak of 1 student who acquired SARS-CoV-2 infection. |
Note: CI = confidence interval. The “model” column indicates whether a sampled or a fixed value was used in the model. We took all samples from the Gaussian distribution. Descriptions of the distribution parameters are provided in Appendix 1A, available at www.cmajopen.ca/content/9/4/E1252/suppl/DC1.