Table 3

Effectiveness of Covishield vaccine against SARS-CoV-2 infection and COVID-9 outcomes in residents of congregate living facilities in India

Exposure groupPerson-months of follow-up*COVID-19 cases (n)Incidence rate
(95% CI) per
1000 person-months
†aHR for
COVID-19 (95% CI);
P value
§Unfavourable outcomes (n)aHR for unfavourable outcomes (95% CI);
P value
Unvaccinated (UV)158712076 (63 to 90)Reference16Reference
First dose of Covishield vaccine12773225 (18 to 35)0.29 (0.18 to 0.46; p<0.001)71%
80.24 (0.07 to 0.82; p=0.023)
Two doses of Covishield vaccine764792 (44 to 19)0.20 (0.09 to 0.44; p<0.001)80%
10.01 (0.001 to 0.10; p<0.001)
Time interval after 1st Dose
 Unvaccinated158712076 (63 to 90)Reference
 14–29 days546111 (50 to 247)0.92 (0.38 to 2.26; p=0.858)
 30–60 days92511 (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.