Age-targeted strategies are often interpreted in extreme ways: "cut off", "perfectly segregate", etc, some part of society, while everyone else "gets on with normal life".

Obviously in this formulation, skepticism is merited. Nothing is perfect, and "cutting" things off...1/9 https://twitter.com/LindaBauld/status/1309551862803312652

sounds hard!

But this is an absolutist interpretation of ideas which should, like most, be interpreted quantitatively. The same misinterpretation could be given for all current strategies, by suggesting that masks, restrictions, etc., aim to "perfectly" stop all transmission. 2/

In fact, the goal of current strategies is to have a quantitative effect on transmission, reducing it for all groups essentially "as much as the market will bear".

In practice, this has involved implementing policies which begin harshly (lockdown), and gradually relax. 3/

Even during periods where policies are constant, individual stamina for mitigations is a finite resource, and we should expect compliance with mitigations to begin decreasing essentially as soon as they begin; indeed we see this directly in movement/social data, and see...

the results in case trajectories. Even when epidemiologists or public health officials hope politicians maintain constant low transmission levels until an effective vaccine is available (because of decreasing compliance, this may require ever-increasing restrictions!), 5/9

this hope should not be the basis for policy.

Age-targeted strategies recognize that when an increase in transmission / cases is in our future, COVID mortality can be decreased by making that increase happen earlier (on average! not perfectly!) for younger age groups. 6/9

Intuitively speaking, it is better for older groups if cases among younger groups occur earlier, before transmission increases have occurred among older groups as well.

It is better, for example, if in-person work begins earlier (on avg) for younger than for older people.
7/9

Quantitatively speaking, this phenomenon can be exhibited in models which incorporate known contact patterns by age (below, for the U.S.) 8/9 https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0236237

This kind analysis does not assume "perfect segregation" or unattainable ideals of separation.

Instead, what it shows is that making transmission increases happen earlier for younger people than for older people will reduce mortality (especially for older people).9/9