Table 2.
Vaccine effectiveness estimates for ChAdOx1 nCoV-19 against COVID-19 hospital admissions or death by length of time since two-dose vaccination in Scotland and Brazil
|
Scotland |
Brazil |
|||||
|---|---|---|---|---|---|---|
| Person-years | Number of events | Vaccine effectiveness* (95% CI) | Person-years | Number of events | Vaccine effectiveness* (95% CI) | |
| Unvaccinated | 336 942 | 2245 | 0% (ref) | .. | .. | .. |
| 0–2 weeks after first dose | 6860 | 39 | −15·4% (−60·6 to 17·0) | 1 849 099 | 21 736 | 0% (ref) |
| Partially vaccinated† | 94 761 | 420 | 49·3% (43·3 to 54·6) | 11 701 310 | 37 802 | 57·9% (56·9 to 58·9) |
| 0–1 week after second dose | 47 252 | 78 | 77·7% (71·9 to 82·3) | 1 601 585 | 2688 | 73·2% (71·9 to 74·5) |
| 2–3 weeks after second dose | 55 318 | 85 | 83·7% (79·7 to 87·0) | 1 492 259 | 1095 | 86·4% (85·4 to 87·3) |
| 4–5 weeks after second dose | 65 698 | 106 | 86·6% (83·6 to 89·0) | 1 338 063 | 1019 | 83·5% (82·3 to 84·7) |
| 6–7 weeks after second dose | 71 120 | 134 | 86·8% (84·2 to 88·9) | 1 117 983 | 1019 | 77·9% (76·1 to 79·5) |
| 8–9 weeks after second dose | 73 540 | 245 | 79·0% (75·9 to 81·7) | 862 976 | 863 | 75·6% (73·4 to 77·6) |
| 10–11 weeks after second dose | 73 212 | 280 | 79·6% (76·8 to 82·1) | 651 213 | 751 | 69·3% (66·3 to 72·1) |
| 12–13 weeks after second dose | 71 773 | 337 | 77·4% (74·6 to 80·0) | 445 924 | 646 | 60·8% (56·6 to 64·6) |
| 14–15 weeks after second dose | 68 114 | 356 | 75·9% (72·9 to 78·6) | 264 128 | 472 | 59·7% (54·6 to 64·2) |
| 16–17 weeks after second dose | 63 974 | 402 | 70·5% (67·0 to 73·7) | 169 692 | 397 | 50·5% (43·4 to 56·6) |
| 18–19 weeks after second dose | 58 608 | 508 | 63·7% (59·6 to 67·4) | 132 459 | 275 | 42·2% (32·4 to 50·6) |
| 20–21 weeks after second dose | 45 716 | 598 | 53·6% (48·4 to 58·3) | .. | .. | .. |
Scotland reference group: unvaccinated, Brazil reference group: 0–13 days after first dose vaccination.
In Scotland, vaccine effectiveness was adjusted for age, sex, deprivation, comorbidities, number of previous tests, interval between doses, and temporal trend; individuals positive for SARS-CoV-2 before Dec 8, 2020, were excluded from the analysis. In Brazil, vaccine effectiveness was adjusted for age, sex, deprivation, macroregion of residence, primary reason for vaccination, interval between doses, and temporal trend.
Partially vaccinated: ≥2 weeks after the first dose and before the second dose.