Climate Etc. By Nic Lewis 7/27/2020
I showed in my May 10th article
Why herd immunity to COVID-19 is reached much earlier than thought that inhomogeneity within a population in the susceptibility and in the social-connectivity related infectivity of individuals would reduce, in my view probably very substantially, the herd immunity threshold (HIT), beyond which an epidemic goes into retreat. I opined, based on my modelling, that the HIT probably lay somewhere between 7% and 24%, and that evidence from Stockholm County suggested it was around 17% there, and had been reached. Mounting evidence supports my reasoning.[1]
I particularly want to highlight an important paper published on July 24th “Herd immunity thresholds estimated from unfolding epidemics†(Aguas et al.).[2] The author team is much the same as that of the earlier theoretical paper (Gomes et al.[3]) that prompted my May 10th article.
Aguas et al. used a SEIR compartmental epidemic model modified to allow for inhomogeneity, similar to the model I used although they also considered further variants. They fitted their models to scaled daily new cases data from four European countries for which disaggregated regional case data was also readily available. In all cases they found a better fit from their models incorporating heterogeneity to the standard homogeneous assumption SEIR model. They found that:
Homogeneous models systematically fail to fit the maintenance of low numbers of cases after the relaxation of social distancing measures in many countries and regions.More:
https://judithcurry.com/2020/07/27/why-herd-immunity-to-covid-19-is-reached-much-earlier-than-thought-update/#more-26449
