Table 2. Efficacy and effectiveness of COVID-19 vaccines against asymptomatic SARS-CoV-2 infection, 1 January–14 May 2021 (n = 7).
| Study | Country | Study design | Study population (n) | Age | Circulating variant | Vaccine | Time point of analysis after vaccine dose | Adjusted vaccine efficacy/effectiveness (95% CI) |
|
|---|---|---|---|---|---|---|---|---|---|
| After dose 1 | After dose 2 | ||||||||
| Angel [32]; 6 May2021 |
Israel | Retrospective cohort study | HCW (n = 6,710) | Mean (SD) all: 44.3 (12.5) years; vaccinated: 44.8 (12.5) years; unvaccinated: 40.7 (11.7) years | Not reported | Comirnaty | 7-28 days after dose 1; > 7 days after dose 2; > 21 days after dose 2 |
36% (IRR: 0.64; 0.31–1.51) | 86% (IRR: 0.14 (0.07–0.31)) 94% (IRR: 0.02 (0–0.06)) |
| EMA Assessment report COVID-19 vaccine Janssen [22]; 11 Mar 2021 |
Multicentre (incl. US, Brazil, South Africa) | RCT (phase 3-licensure trial) | Vaccine group (n = 19,306); placebo group (n = 19,178) | ≥ 18 years | Beta (B.1.351) (); Zeta (P.2); D614G-carrying ‘WT/ref’ | COVID-19 vaccine Janssen | > 28 days after vaccination | 74% (27.9–92.4) | Not applicable |
| Haas [11]; 24 Mar 2021 | Israel | Cohort study | Surveillance data (national); n = 202,684 SARS-CoV-2 infections; n = 102,012 non-vaccinated | ≥ 16 years | Alpha (B.1.1.7) (94.5%) | Comirnaty | ≥ 7 days after dose 2; ≥ 14 days after dose 2 |
Not reported | 91.5% (90.7–92.2) 93.8% (93.3–94.2) |
| Jones [21]; 8 Apr 2021 |
UK | Retrospective cohort study | HCW (n = 8,776) |
Adults | Mainly Alpha (B.1.1.7 ) | Comirnaty | ≥ 12 days after dose 1 | 75%a | Not reported |
| Tande [19]; 10 Mar 2021b |
US | Retrospective cohort study | Population-based; patients at Mayo Clinics (n = 39,156) | ≥ 18 years, Mean: 54,2 years (SD 19.7) | Not reported | Comirnaty; Moderna | > 10 days after dose 1; > 0 days after dose 2 |
79% (RR: 0.21 (0.12–0.37)) Comirnaty only: 79% (RR = 0.21 (0.11–0.38)) |
80% (RR: 0.20 (0.09–0.44)) Comirnaty only: 80% (RR: 0.20 (0.09–0.44)) |
| Tang [31]; 6 May2021 |
US | Cohort study | HCW (n = 5,217) | Adults | Not reported | Comirnaty | ≥ 12 days after dose 1 and before dose 2; ≥ 7 days after dose 2 |
42% (IRR: 0.58 (0.30–1.13)) | 90% (IRR: 0.10 (0.04–0.22)) |
| Zacay [20]; 3 Mar 2021b |
Israel | Retrospective cohort study | Insurance members (n = 6,286) |
≥ 16 years | Mainly Alpha, (B.1.1.7) also Beta (B.1.351 ) | Comirnaty | ≥ 14 days after dose 1; ≥ 7 days after dose 2 |
61% (49–71) | 89% (82–94) |
CI: confidence interval; COVID-19: coronavirus disease; HCW: healthcare workers; IRR: incidence rate ratio; RCT: randomised controlled trial; RR: risk ratio; SARS-CoV-2: severe acute respiratory syndrome coronavirus 2; SD: standard deviation; UK: United Kingdom; US: United States.
aOwn calculation.
bPreprint.