Table 2.
Critical vaccination coverage (Vc) required to establish herd immunity against SARS-CoV-2 with reproductive numbers (Ro) from 1.1 to 10 by vaccination effectiveness (%), with 9.8% of infections among vaccinated individuals.
| Ro of SARS-CoV-2 b | Critical Vaccination Coverage (%) a
For COVID-19 Vaccination Effectiveness from 10% to 100% |
|||||||||
|---|---|---|---|---|---|---|---|---|---|---|
| 10% | 20% | 30% | 40% | 50% | 60% | 70% | 80% | 90% | 100% | |
| 1.1 | − | 89.1 | 45.0 | 30.1 | 22.6 | 18.1 | 15.1 | 13.0 | 11.3 | 10.1 |
| 1.25 | − | − | 99.0 | 66.2 | 49.8 | 39.8 | 33.2 | 28.5 | 24.9 | 22.2 |
| 1.5 | − | − | − | − | 82.9 | 66.4 | 55.4 | 47.5 | 41.6 | 37.0 |
| 1.75 | − | − | − | − | − | 85.4 | 71.2 | 61.1 | 53.4 | 47.5 |
| 2 | − | − | − | − | − | 99.6 | 83.1 | 71.2 | 62.3 | 55.4 |
| 2.25 | − | − | − | − | − | − | 92.3 | 79.1 | 69.3 | 61.6 |
| 2.5 | − | − | − | − | − | − | 99.7 | 85.5 | 74.8 | 66.5 |
| 2.75 | − | − | − | − | − | − | − | 90.7 | 79.3 | 70.6 |
| 3 | − | − | − | − | − | − | − | 95.0 | 83.1 | 73.9 |
| 3.25 | − | − | − | − | − | − | − | 98.6 | 86.3 | 76.8 |
| 3.5 | − | − | − | − | − | − | − | − | 89.1 | 79.2 |
| 3.75 | − | − | − | − | − | − | − | − | 91.4 | 81.3 |
| 4 | − | − | − | − | − | − | − | − | 93.5 | 83.1 |
| 4.25 | − | − | − | − | − | − | − | − | 95.3 | 84.8 |
| 4.5 | − | − | − | − | − | − | − | − | 97.0 | 86.2 |
| 4.75 | − | − | − | − | − | − | − | − | 98.4 | 87.5 |
| 5 | − | − | − | − | − | − | − | − | 99.8 | 88.7 |
| 6 | − | − | − | − | − | − | − | − | − | 92.4 |
| 7 | − | − | − | − | − | − | − | − | − | 93.8 |
| 8 | − | − | − | − | − | − | − | − | − | 98.5 |
| 9 | − | − | − | − | − | − | − | − | − | 97.0 |
| 10 | − | − | − | − | − | − | − | − | − | 99.8 |
a Vc = Ic/Effectiveness. Ic = 1 − (1/Ro). The critical vaccination coverage is not indicated (−) when herd immunity could not be established with 100% vaccination coverage. b The basic reproduction number Ro indicates the average number of secondary cases generated per infected case in a completely susceptible population.