3 ms·
City in Brazil where Covid ran amok may be a sentinel for the rest of the world
- jnxx 6y agoOne thing is that the prevalence of infection with subsequent immunity which has "herd immunity" without mass vaccination as a result, depends on the R factor. This is because immunity lowers the number of people which the infection can spread to. If somebody is infected and could infect, on average, 5 more people, but 4 of them already have immunity, then he/she can only infect only 1 person, so the actual R factor is 1. And if the R factor falls below 1, the epidemic will, ideally, die out. So, if the R factor without any immunity was R0, the ratio F of immunity needed is F so that F combined with R0 yields 1. However, what people who see "herd immunity" (without a vaccination) as a strategy is that the R factor in turn depends on collective behavior. It is not constant. If people go a lot to bars, R is surely higher than when they stay at home. And so is F.