Conditional Herd Immunity
The basic reproduction number, R0, for COVID-19 is estimated to be 2.5. With this level of R0, herd immunity is reached when 60% of the population have been infected or recovered. During the COVID-19 epidemic, governments are encouraging/ordering the population to vary their behavior so that the effective value of R is considerably less than 2.5. This raises the prospect of a population reaching herd immunity with only 20% of the population being infected or recovered. This would be conditional herd immunity as it would be conditional on the population maintaining the lower value of R even after the number of infections starts to drop.
Based on a detailed analysis we present the countries listed in order of the expected time to reach conditional herd immunity.
| Rank | Country | Years to Herd Immunity | Immunity (%) | R values | TII (ppm) | Strategy |
|---|---|---|---|---|---|---|
| 141 | Nicaragua | 75.72 | 0.44 | 1.02 | 6.78 | |
| 142 | Guinea-Bissau | 100.06 | 0.56 | 1.05 | 20.98 | |
| 143 | Malawi | 109.01 | 0.99 | 0.64 | 21.4 | |
| 144 | Singapore | 125.9 | 1.08 | 1.03 | 22.21 | |
| 145 | Mozambique | 116.52 | 0.44 | 0.78 | 18.03 | |
| 146 | Chad | 147.71 | 0.18 | 1.19 | 17.77 | |
| 147 | Benin | 149.81 | 0.14 | 1.46 | 22.98 | |
| 148 | Australia | 160.09 | 0.57 | 1.46 | 16.39 | |
| 149 | Mauritius | 239.75 | 0.21 | 0.19 | 5.06 | |
| 150 | Haiti | 249.62 | 0.36 | 1.15 | 12.93 |