COMING TO TERMS WITH HETEROGENEOUS SUSCEPTIBILITY.

That's something economists noticed as an omitted variable in the early pandemic modelling.

There has been enough time now for some pretty good researchers to tackle the omission.  "Acemoglu, Daron, Victor Chernozhukov, Iván Werning and Michael D. Whinston. 2021. 'Optimal Targeted Lockdowns in a Multigroup SIR Model.' American Economic Review: Insights, 3(4):487-502."

The full article is available to Association members or on a pay-per-view basis, but the authors get no royalties, and your local university library might have an institutional subscription for a closer look.

The abstract is promising.

We study targeted lockdowns in a multigroup SIR model where infection, hospitalization, and fatality rates vary between groups—in particular between the "young," the "middle-aged," and the "old." Our model enables a tractable quantitative analysis of optimal policy. For baseline parameter values for the COVID-19 pandemic applied to the US, we find that optimal policies differentially targeting risk/age groups significantly outperform optimal uniform policies and most of the gains can be realized by having stricter protective measures such as lockdowns on the more vulnerable, old group. Intuitively, a strict and long lockdown for the old both reduces infections and enables less strict lockdowns for the lower-risk groups.

The shame is that the findings are consistent with "protect the vulnerable, let the young live free," which has become more of a political litmus test than a point of discussion for policy.  Watch for the article to receive much more media attention on some platforms than others.