Table 1.
Baseline characteristics of studies investigating vaccination before SARS-CoV-2 infection.
| First author | Study design | Country | Observational period | Vaccine type | Follow-up duration (months) | Patient number, N | Age, median [IQR] or mean ± SD | Female, N (%) | ICU admission, N (%) |
|---|---|---|---|---|---|---|---|---|---|
| Meza-Torres[22] | Retrospective cohort | UK | Mar 2020-Apr 2021 | NA | 6 | No vaccination, 392,324; 1-dose, 15,832; 2-dose, 726 | 45 ± 22 | 232,775 (56)a | 2,852 (0.7)a |
| Emecen[23] | Prospective cohort | Turkey | Dec 2020-May 2021 | CoronaVac, BNT162b2 | 6 | No vaccination, 4,847; 2-dose, 162 | 18–49, 67.7 %; 50–64, 22.4 %; 65-, 9.9 % | 2,908 (52)a | 66 (1.3)a |
| Al-Aly[16] | Retrospective cohort | USA | Jan 2021-Dec 2021 | BNT162b2, mRNA-1273, Ad26.COV2.S | 6 | No vaccination, 113,474; 2-dose, 33,940 | No vaccination, 58 ± 16; 2-dose, 67 ± 14 | No vaccination, 14,842 (13); 2-dose, 3,044 (9) | No vaccination, 2,982 (2.6); 2-dose, 811 (2.4) |
| Zisis[24] | Retrospective cohort | USA | Sep 2020-Dec 2021 | NA | 3 | No vaccination, 25,225; 2-dose, 25,225 | No vaccination, 55 ± 18; 2-dose, 55 ± 18 | No vaccination, 15,129 (60); 2-dose, 15,094 (60) | NA |
| Azzolini[17] | Retrospective cohort | Italy | Mar 2020-Apr 2022 | BNT162b2 | 1 | No vaccination, 421; 1-dose, 10; 2-dose, 46; 3-dose, 262 | 44 ± 11 | 180 (33) | NA |
| Antonelli[25] | Prospective cohort | UK | Dec 2020-Jul 2021 | BNT162b2, mRNA-1273, AZD1222 | 1 | 1-dose, 6,030; 2-dose, 2,370 | 1-dose, 50 ± 14; 2-dose, 53 ± 14 | 1-dose, 3,766 (63); 2-dose, 1,451 (61) | NA |
NA, not available.
a
Among patients infected with SARS-CoV-2.