Table 2.
Covid-19 vaccine effectiveness for primary and secondary analyses, with calendar time as the model time-scale.*
| Analysis | Vaccinated |
Unvaccinated |
VE |
|||||
|---|---|---|---|---|---|---|---|---|
| Person-days | Positive cases | Incidence rate per 10,000 person-days | Person-days | Positive cases | Incidence rate per 10,000 person-days | Unadjusted (1-HR) |
Adjusted (1-HR) |
|
| Two-dose VE against any infection | 68,574 | 4 | 0.58 | 10,027 | 9 | 8.98 | 95.4% (84.8%-98.6%) | 94.5% (82.6%-98.2%) |
| Two-dose VE against symptomatic infection | 68,605 | 2 | 0.29 | 10,027 | 9 | 8.98 | 97.4% (88%-99.4%) | 97% (72%-99.7%) |
| Two-dose VE against any infection (14 days after second dose) | 61,620 | 4 | 0.65 | 10,027 | 9 | 8.98 | 95.4% (84.8%-98.6%) | 94.5% (82.5%-98.2%) |
| Two-dose VE against any infection including participants regardless of how many weekly specimens they provided (Extended Cohort 1)** | 67,230 | 4 | 0.59 | 9229 | 9 | 9.75 | 95.6% (85.6%-98.7%) | 94.8% (83.4%-98.4%) |
| Two-dose VE against any infection, excluding only participants who were seropositive at enrollment and/or PCR-positive before or at enrollment (Extended Cohort 2) | 75,388 | 6 | 0.80 | 10,888 | 10 | 9.18 | 94% (83.3%-97.8%) | 92.3% (80.5%-96.9%) |
Notes: *All VE analyses were performed for two-dose vaccination with follow-up beginning 7 days after second vaccine unless specified otherwise.
**Extended Cohort 1 included participants who had a negative enrollment serology and were not previously infected by PCR, regardless of how many weekly specimens they provided during the follow-up period.
Abbreviations VE, vaccine effectiveness HR, hazards ratio PCR, polymerase chain reaction