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 |
|---|---|---|---|---|---|---|
| 1 | Peru | -0.89 | 95.92 | 0.98 | 6236.32 | |
| 2 | Bosnia and Herzegovina | -0.56 | 45.62 | 0.82 | 264.02 | |
| 3 | North Macedonia | -0.52 | 41.25 | 0.7 | 121.57 | |
| 4 | Belgium | -0.51 | 34.9 | 0.9 | 804.04 | |
| 5 | Moldova | -0.48 | 35.84 | 1.05 | 317.21 | |
| 6 | Montenegro | -0.47 | 40.57 | 0.9 | 326.59 | |
| 7 | San Marino | -0.47 | 41.48 | 5.0 | 0.0 | |
| 8 | Hungary | -0.46 | 48.16 | 0.79 | 233.09 | |
| 9 | United Kingdom | -0.45 | 30.87 | 1.22 | 3223.63 | |
| 10 | Bulgaria | -0.45 | 40.35 | 0.81 | 398.17 |