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 | Belgium | -0.32 | 31.7 | 1.0 | 4307.15 | |
| 2 | San Marino | -0.21 | 38.36 | 1.23 | 15207.04 | |
| 3 | Bosnia and Herzegovina | -0.2 | 24.84 | 0.76 | 2115.82 | |
| 4 | North Macedonia | -0.18 | 25.1 | 1.26 | 5353.55 | |
| 5 | Bulgaria | -0.17 | 24.77 | 1.23 | 7031.6 | |
| 6 | Slovenia | -0.17 | 31.2 | 1.0 | 5169.81 | |
| 7 | Hungary | -0.17 | 26.75 | 1.39 | 12496.3 | |
| 8 | Italy | -0.16 | 27.49 | 1.2 | 7583.63 | |
| 9 | United Kingdom | -0.16 | 30.43 | 0.77 | 2632.55 | |
| 10 | Liechtenstein | -0.15 | 22.76 | 1.68 | 1625.99 |