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 | Moldova | -0.15 | 25.07 | 1.2 | 7588.06 | |
| 12 | US | -0.15 | 25.87 | 0.95 | 2789.58 | |
| 13 | Montenegro | -0.13 | 28.51 | 1.13 | 9448.15 | |
| 14 | Croatia | -0.13 | 21.75 | 1.17 | 1644.56 | |
| 15 | Panama | -0.12 | 22.76 | 0.94 | 1820.12 | |
| 16 | Andorra | -0.11 | 23.45 | 0.96 | 2431.56 | |
| 17 | Mexico | -0.11 | 24.55 | 0.97 | 3069.28 | |
| 18 | Peru | -0.11 | 24.69 | 0.93 | 5728.77 | |
| 19 | Portugal | -0.11 | 26.4 | 0.72 | 1396.72 | |
| 20 | Spain | -0.1 | 24.83 | 0.81 | 2612.92 |