Thread by @mgmgomes1

@PieterTrapman @mlipsitch 1/ Unclear what you mean by these numbers, but a week later I finally had a couple of hours on a Saturday to have a look. Running the models in our July preprint I am now comparing the 70% lower-risk group with the whole population. Here is what I find (explanations follow).

@PieterTrapman @mlipsitch 2/ I run each of the 3 models until the pandemic is over (one year is sufficient for these models). Then I calculate the proportion of the 70% lower-risk group that has been infected and divide by the portion of the entire population that has been infected.

@PieterTrapman @mlipsitch 3/ This metric varies wildly across models even though all assumed a gamma distribution with mean=1 and coefficient of variation estimated by fitting to first wave of confirmed cases in specific countries. I calculate HIT for each case and find this to be conserved across models.

@PieterTrapman @mlipsitch 4/ Finally I calculate relative risk between 70% lower-risk group and entire population and find lower values than those for relative infected proportions. Even though I was unclear of what you were suggesting I suspect this is the metric you were interested in.

@PieterTrapman @mlipsitch 5/ Lots to discuss here. First important to realise that the relative risk as assessed directly from risk distributions is NOT what will be observed when we look at actual cases. Here is a great Review by Odd Aalen et al on "the elusive concept of frailty" ncbi.nlm.nih.gov/pmc/articles/P…

@PieterTrapman @mlipsitch The above paper was really eye opening to me and I strongly recommend it to anyone interested in individual variation in epidemiology (whether non-communicable or infections diseases).

@PieterTrapman @mlipsitch 7/ Second, HIT is conserved across models fitted to the same data while those relative measures between 70% lower-risk group and entire population are not. So it seems a distraction that we cannot afford; the pandemic is here and we can make more productive use of our time.

@PieterTrapman @mlipsitch 8/ Third, setting susceptibilities to absolute zero doesn't seem a good idea as this leads to system degeneracy (described in the context of vaccines by myself @mlipsitch @GrahamMedley and others): journals.plos.org/plospathogens/…

@PieterTrapman @mlipsitch @GrahamMedley 9/ Finally, I think we should be more responsible and avoid going public with potentially void concerns about the work of others. It can hugely time consuming and damaging not only for the authors but for scientific progress. This is meant as a general statement.