Table 3.
Vaccine effectiveness estimates for ChAdOx1 nCoV-19 against confirmed SARS-CoV-2 symptomatic infection by length of time since two-dose vaccination in Scotland and Brazil using a test-negative design case-control study
|
Scotland |
Brazil |
|||||
|---|---|---|---|---|---|---|
| Total samples | Positive samples | Vaccine effectiveness* (95% CI) | Total samples | Positive samples | Vaccine effectiveness* (95% CI) | |
| Unvaccinated | 26 130 | 13 698 | 0% (ref) | 9 852 053 | 4 920 001 | 0% (ref) |
| 0–1 week after first dose | 911 | 374 | 20·9% (8·2 to 31·9) | 286 322 | 151 328 | −9·6% (−10·5 to −8·8) |
| Partially vaccinated† | 15 714 | 7176 | 37·6% (34·6 to 40·5) | 1 143 423 | 398 717 | 37·6% (37·3 to 37·9) |
| 0–1 week after second dose | 5027 | 2025 | 50·2% (46·7 to 53·5) | 112 391 | 30 550 | 51·3% (50·6 to 52·0) |
| 2–3 weeks after second dose | 7141 | 2429 | 67·9% (65·9 to 69·8) | 95 671 | 7963 | 69·8% (69·3 to 70·4) |
| 4–5 weeks after second dose | 8947 | 3387 | 67·3% (65·3 to 69·1) | 79 298 | 15 568 | 68·4% (67·8 to 68·9) |
| 6–7 weeks after second dose | 10 622 | 4346 | 63·8% (61·7 to 65·7) | 60 301 | 12 401 | 66·8% (66·1 to 67·5) |
| 8–9 weeks after second dose | 11 258 | 4633 | 63·3% (61·3 to 65·3) | 44 351 | 9424 | 65·4% (64·6 to 66·2) |
| 10–11 weeks after second dose | 14 043 | 6319 | 59·3% (57·2 to 61·4) | 32 832 | 7103 | 63·2% (62·2 to 64·2) |
| 12–13 weeks after second dose | 17 300 | 7966 | 55·3% (53·0 to 57·5) | 22 454 | 5177 | 58·8% (57·4 to 60·1) |
| 14–15 weeks after second dose | 17 421 | 7670 | 52·9% (50·4 to 55·2) | 15 305 | 3435 | 59·8% (58·2 to 61·4) |
| 16–17 weeks after second dose | 15 442 | 6554 | 48·7% (45·9 to 51·4) | 10 822 | 2529 | 58·7% (56·7 to 60·5) |
| 18–19 weeks after second dose | 14 403 | 6248 | 44·6% (41·5 to 47·6) | 7458 | 1852 | 57·7% (55·4 to 60·0) |
| 20–21 weeks after second dose | 10 596 | 4718 | 39·1% (35·4 to 42·6) | .. | .. | .. |
In Scotland, vaccine effectiveness was adjusted for age, sex, deprivation, comorbidities, number of at-risk groups, smoking status, blood pressure, body-mass index, health board, interval between doses, and temporal trend. In Brazil, vaccine effectiveness was adjusted for age, sex, deprivation, macroregion of residence, diabetes, obesity, immunosuppression, cardiac disease, pregnancy, puerperal period, chronic kidney disease, and temporal trend. Descriptive characteristics for the sample are available in appendix 2 (pp 11–15).
Partially vaccinated: ≥2 weeks after the first dose and before the second dose.