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 | -0.42 | 34.74 | 0.96 | 5496.92 | |
| 2 | Bosnia and Herzegovina | -0.38 | 41.74 | 0.99 | 9678.67 | |
| 3 | North Macedonia | -0.33 | 37.12 | 0.83 | 7406.13 | |
| 4 | Moldova | -0.31 | 34.46 | 0.84 | 3513.83 | |
| 5 | San Marino | -0.31 | 43.06 | 0.66 | 2800.49 | |
| 6 | Hungary | -0.3 | 46.13 | 0.76 | 10246.48 | |
| 7 | Bulgaria | -0.3 | 38.49 | 0.81 | 8374.65 | |
| 8 | Montenegro | -0.29 | 37.92 | 0.85 | 3343.25 | |
| 9 | United Kingdom | -0.28 | 30.29 | 1.04 | 818.34 | |
| 10 | Slovenia | -0.28 | 33.38 | 0.85 | 4544.86 |