Effectiveness of Covishield vaccine against SARS-CoV-2 infection and COVID-9 outcomes in residents of congregate living facilities in India
| Exposure group | Person-months of follow-up | *COVID-19 cases (n) | Incidence rate (95% CI) per 1000 person-months | †aHR for COVID-19 (95% CI); P value | ‡VE (%) | §Unfavourable outcomes (n) | aHR for unfavourable outcomes (95% CI); P value |
| Unvaccinated (UV) | 1587 | 120 | 76 (63 to 90) | Reference | – | 16 | Reference |
| First dose of Covishield vaccine | 1277 | 32 | 25 (18 to 35) | 0.29 (0.18 to 0.46; p<0.001) | 71% (54%–82%) | 8 | 0.24 (0.07 to 0.82; p=0.023) |
| Two doses of Covishield vaccine | 764 | 7 | 92 (44 to 19) | 0.20 (0.09 to 0.44; p<0.001) | 80% (56%–91%) | 1 | 0.01 (0.001 to 0.10; p<0.001) |
| Time interval after 1st Dose | |||||||
| Unvaccinated | 1587 | 120 | 76 (63 to 90) | Reference | – | – | – |
| 14–29 days | 54 | 6 | 111 (50 to 247) | 0.92 (0.38 to 2.26; p=0.858) | – | – | – |
| 30–60 days | 925 | 1 | 1 (0.2 to 7.7) | 0.01 (0.002 to 0.10; p<0.001) | – | – | – |
*COVID-19 cases for vaccine effectiveness analysis were restricted to those happening after the first or second dose of vaccine. Therefore, total cases (n=159) in this table differ from that of figure 2D (n=341).
†HR adjusted for age, sex, residence type, current smoking status, hypertension, diabetes, chronic obstructive pulmonary disease, cardiovascular disease and chronic hepatitis B virus infection.
‡Vaccine effectiveness = (1−HR)×100%.
§Unfavourable clinical outcomes defined as those developing shortness of breath/use of supplemental oxygen, hospitalised or who died after 14 days of vaccine administration.
aHR, adjusted HR.