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 |
|---|---|---|---|---|---|---|
| 11 | Croatia | -0.32 | 30.87 | 0.82 | 6882.94 | |
| 12 | Slovenia | -0.32 | 33.97 | 1.02 | 4835.04 | |
| 13 | Liechtenstein | -0.31 | 24.93 | 0.66 | 1994.32 | |
| 14 | Slovakia | -0.31 | 35.14 | 0.86 | 1823.51 | |
| 15 | Mexico | -0.3 | 27.7 | 0.84 | 1525.06 | |
| 16 | Italy | -0.29 | 33.34 | 0.86 | 4034.78 | |
| 17 | Panama | -0.29 | 23.78 | 1.02 | 1056.64 | |
| 18 | Portugal | -0.28 | 26.06 | 0.83 | 517.28 | |
| 19 | Brazil | -0.28 | 33.7 | 1.02 | 7195.57 | |
| 20 | Spain | -0.28 | 26.62 | 0.82 | 2609.71 |