Association between participant characteristics and testing positive for COVID-19 infection
| Characteristic | Per cent testing positive | Bivariate OR (95% CI) | Full multivariable model OR (95% CI) | Final multivariable model OR (95% CI) |
| Age, years | ||||
| 5–17 | 1.6 | 1.02 (0.44 to 2.41) | 1.14 (0.52 to 2.48) | 1.12 (0.47 to 2.63) |
| 18–34 | 2.3 | 1.48 (0.84 to 2.58) | 1.65 (0.93 to 2.91) | 1.64 (0.93 to 2.87) |
| 35–49 | 3.1 | 2.04 (1.18 to 3.54) | 1.99 (1.14 to 3.49) | 2.08 (1.20 to 3.62) |
| 50–64 | 1.7 | 1.08 (0.62 to 1.90) | 1.08 (0.61 to 1.89) | 1.10 (0.63 to 1.93) |
| ≥65 | 1.6 | Referent | Referent | Referent |
| Sex | ‡ | |||
| Female | 2.0 | Referent | Referent | |
| Male | 2.2 | 1.09 (0.83 to 1.44) | 1.10 (0.83 to 1.46) | |
| Mode of travel | ‡ | |||
| Air | 2.2 | Referent | Referent | |
| Land | 1.8 | 0.84 (0.53 to 1.35) | 1.00 (0.62 to 1.63) | |
| Nationality | ‡ | |||
| Canadian citizen | 2.3 | 2.13 (1.04 to 4.34) | 1.52 (0.68 to 3.40) | |
| Canadian permanent resident | 2.0 | 1.84 (0.78 to 4.32) | 1.28 (0.50 to 3.26) | |
| Foreign citizen | 1.1 | Referent | Referent | |
| Country of residence | ||||
| Canada | 2.4 | 2.21 (1.40 to 3.48) | 1.97 (1.07 to 3.63) | 2.21 (1.39 to 3.51) |
| All others | 1.1 | Referent | Referent | Referent |
| Days absent from Canada | ‡ | |||
| Up to 14 days | 2.7 | 1.39 (1.03 to 1.86) | 1.21 (0.89 to 1.64) | |
| ≥14 days | 1.9 | Referent | Referent | |
| N/A | 1.2 | 0.61 (0.35 to 1.06) | 1.14 (0.55 to 2.36) | |
| Departure country 14-day risk category* | ‡ | |||
| Green | 0.0 | 0.40 (0.02 to 6.50) | ||
| Yellow | 0.9 | 0.62 (0.12 to 3.12) | † | |
| Red | 2.1 | Referent | ||
| Unknown | 3.1 | 1.51 (0.91 to 2.52) | ||
| Departure country 14-day smoothed positivity rate | ||||
| ≤0.2 | 1.9 | Referent | Referent | Referent |
| >0.2 | 3.0 | 1.60 (1.15 to 2.22) | 3.52 (1.75 to 7.09) | 3.30 (1.68 to 6.46) |
| Unknown | 3.1 | 1.67 (1.00 to 2.79) | 4.15 (1.71 to 10.07) | 3.82 (1.61 to 9.05) |
| Departure country 14-day notification rate per 100 000 | ||||
| ≤200 | 2.5 | Referent | Referent | Referent |
| >200 | 2.0 | 0.81 (0.57 to 1.14) | 2.87 (1.38 to 5.99) | 2.62 (1.30 to 5.31) |
Smoothed positivity refers to the proportion of within-country COVID-19 tests reported as positive, averaged over 7 days for the departure country. Notification rate refers to the 14-day rate of within-country COVID-19 infection per 100 000 population. Positivity and notification rate were based on data from ourworldindata.org for the departure country, assessed at the arrival date. The 14-day risk category was based on the positivity and notification rate, using the heat map at reopen.europa.eu/en.
The Hosmer Lemeshow goodness-of-fit test for the final multivariable model: p=0.54.
*There were no positive cases among the 57 participants who had arrived from green (low risk) countries, so a bivariate OR could not be calculated using maximum likelihood procedures. Instead, ORs were estimated using penalised maximum likelihood methods.
†The risk category was not included in the full model as it was derived from positivity and case rate, and because 98% of participants whose departure country was known were classified as high risk.
‡These variables were dropped from the final multivariable model as they were non-significant in the full model.