Participant characteristics of included studies (N=41)
| Count of studies | % of studies | ||
| Sample size | ≤500 | 14 | 34% |
| 501–≤1000 | 6 | 15% | |
| 1001–≤3000 | 12 | 29% | |
| 3001+ | 9 | 22% | |
| Eligible age group included (years) | ≥60 | 7 | 17% |
| ≥65 | 34 | 83% | |
| % female | ≤50% | 8 | 20% |
| 51%–60% | 19 | 46% | |
| 61%–75% | 11 | 27% | |
| Not reported | 3 | 7% | |
| Race | Reported races other than white/Caucasian* | 19 | 46% |
| Reported race as only white/Caucasian | 8 | 20% | |
| Not reported | 14 | 34% | |
| Vaccination history | ≤60% | 2 | 5% |
| 61%–80% | 3 | 7% | |
| 81%–100% | 7 | 17% | |
| Not reported | 29 | 71% | |
| Frailty history | Yes | 3 | 7% |
| Not reported | 38 | 93% | |
| Comorbidities | Reported >2 comorbidities | 9 | 22% |
| Reported a comorbidity score | 4 | 10% | |
| Not reported | 28 | 68% | |
*White/Caucasian race in these studies ranged between 0% and 98%.