Table. Key Assumptions and Evidence Informing Those Assumptions.
| Source | Evidence base | Estimate or assumption |
|---|---|---|
| Assumptions for presymptomatic transmission | ||
| Peak infectiousness relative to onset, d | ||
| Casey et al, 202018 | Range, 17 studies | −3 to 1.2 d |
| Assumed baseline | NA | 0 d |
| Assumed range | NA | −2 to 2 d |
| Assumptions for never symptomatic transmission | ||
| Proportion never symptomatic | ||
| Oran et al, 202012 | Inferred range, 16 studies | 30% to 45% |
| Buitrago-Garcia et al, 202014 | Meta-estimate, 7 studies | 26% to 37% |
| Davies et al, 202020 | Age-dependent estimate, 6 studies | 20% to 70% |
| Assumed baseline | NA | 30% |
| Relative infectiousness of individuals who never have symptoms | ||
| Lee et al, 20209 | 303 patients, assessment of viral shedding | Approximately 100% |
| Chaw et al, 202015 | 1701 secondary contacts | 40% to 140% |
| Mc Evoy et al, 202016 | Inferred range, 6 studies | 40% to 70% |
| Assumed baseline | 75% | |
| Overall proportion of individuals who never have symptoms transmission | ||
| Assumed range | NA | 0% to 70% |
Abbreviation: NA, not applicable.