4 ms·
> So we are still a long way off herd immunity. But at the same time closer than we thought we were. Yes and no. A disease is endemic when R0 x S = 1 [0]. R0
by ignoramous 7y ago
> So we are still a long way off herd immunity. But at the same time closer than we thought we were.
Yes and no.
A disease is endemic when R0 x S = 1 [0]. R0 for SARS-CoV-2 is estimated to be 2.5 to 3.5 and some models predicting a much higher 5.7 [1].
The herd immunity threshold is given by (1 - S)%, which implies when R0 = 2.5, 60% of the population would need to be immune; similarly 71.42% and 82.45% for R0s, 3.5 and 5.7, respectively.
[0] https://en.wikipedia.org/wiki/Endemic_(epidemiology) https://en.wikipedia.org/wiki/Endemic_(epidemiology)
[1] https://news.ycombinator.com/item?id=22817942 https://news.ycombinator.com/item?id=22817942
- fiftyfifty 7y agoWhat percentage of immunity can we expect to see a slowdown in the spread of the disease? While we may need 60% or more to achieve full herd immunity surely somewhere lower than that we can expect to see a noticeable reduction in the spread?
- ignoramous 7y ago> ...noticeable reduction in the spread? I believe the SIR model [0] answers those questions. 3blue1brown's video on the topic is super digestible and informative [1]. In short, the discovery of a prophylactic if not a therapeutic treatment are our best immediate bets, absent which, quarantines and lockdowns will have to persist to curb the spread of a disease as infectious as covid-19 whilst we patiently wait for an effective vaccine against it [2]. [0] https://en.wikipedia.org/wiki/Compartmental_models_in_epidemiology#The_SIR_model https://en.wikipedia.org/wiki/Compartmental_models_in_epidem... [1] https://www.youtube.com/watch?v=gxAaO2rsdIs https://www.youtube.com/watch?v=gxAaO2rsdIs [2] https://en.wikipedia.org/wiki/Vaccine_efficacy https://en.wikipedia.org/wiki/Vaccine_efficacy