Table. Estimated Incidence Rate Ratio Against Any SARS-CoV-2 Infection and Asymptomatic or Symptomatic/Contact SARS-CoV-2 Infectiona.
| Vaccination status | Follow-up time, person-days (No. at risk) | Any positive test result | Asymptomatic screening positive test result | Screening positive test result based on the presence of symptoms or known COVID-19 exposure | |||
|---|---|---|---|---|---|---|---|
| No. | IRR (95% CI)b | No. | IRR (95% CI) | No. | IRR (95% CI) | ||
| Unvaccinated total follow-upc | 149 718 (2165) | 185 | 79 | 106 | |||
| Vaccinated total follow-up | 198 480 (3052) | 51 | 0.21 (0.15-0.28) | 29 | 0.28 (0.18-0.42) | 22 | 0.16 (0.10-0.25) |
| Vaccinated periods | |||||||
| 0-11 d after dose 1 | 32 807 (3052) | 24 | 0.59 (0.39-0.91) | 10 | 0.58 (0.30-1.12) | 14 | 0.60 (0.35-1.05) |
| ≥12 d after dose 1 and before dose 2 | 32 481 (2942) | 17 | 0.42 (0.26-0.70) | 10 | 0.58 (0.30-1.13) | 7 | 0.30 (0.14-0.65) |
| 0-6 d after dose 2 | 16 492 (2776) | 4 | 0.20 (0.07-0.53) | 3 | 0.35 (0.11-1.09) | 1 | 0.09 (0.01-0.61) |
| ≥7 d after dose 2 | 116 700 (2724) | 6 | 0.04 (0.02-0.09) | 6 | 0.10 (0.04-0.22) | 0 | 0d |
Abbreviation: IRR, incidence rate ratio.
Follow-up periods for unvaccinated employees began on December 17, 2020, or on their first asymptomatic screening date, whichever was later. Individuals who received vaccines other than BNT162b2 were censored on vaccination. Follow-up periods for vaccinated workers began when they received their first dose. Workers who remained SARS-CoV-2 negative during follow-up were censored on March 20, 2021, or on the employment termination date, whichever was earlier. No person contributed to both groups. Individuals with prior COVID-19 exposure were excluded.
Incidence rate ratio is the ratio of confirmed COVID-19 cases per person-days of follow-up in vaccinated compared with unvaccinated groups.
The unvaccinated group was treated as the reference group for all calculations.
95% CI does not apply.