Thread by @AdamJKucharski

Suggestions to include spontaneous behavioural responses to a growing epidemic as default in scenario models might sound simple and obvious, but it's worth considering the assumptions involved... 1/

What magnitude of behaviour change in response to epidemic would you assume as a baseline scenario? And how would this relate to transmission reduction? 2/

Would you assume disruptive-but-ineffective change (e.g. avoiding low risk interactions and continuing to have high risk ones) or well-targeted change (e.g. using more rapid tests effectively)? 3/

And what would you assume are the trigger points for this change? Rising cases/hospitalisations/deaths nationally? Media speculation about policy changes? Infections in people's first or second degree local social network? Spread of attitudes in social groups? All of these? 4/

If you're extrapolating patterns from other settings (e.g. earlier waves in places without stringent policies) how would you adjust for confounders like sick leave policies, test availability, increased vaccine coverage etc? 5/

Would you assume people will be less spontaneously cautious because they've been vaccinated, or more cautious because of variant uncertainty and knowledge of potential for waning responses? 6/

Or, for simplicity, would you assume behaviour just changes at specific points in time to go back to earlier stages of the epidemic, and show the resulting dynamics (which is what some models have previously done, e.g. below) 7/

https://twitter.com/AdamJKucharski/status/1481193339517087748?s=20

Scenario that assume 'no change' in behaviour are clearly making a strong assumption. But as above illustrates, deviations from this scenario also require strong assumptions, often with multiple decision points... 8/

This shows the value of thinking through steps involved and assumptions that would be required, rather than just saying 'oh well, obviously X would happen...' 9/

It will gradually become clear how behaviour changed in different locations independent of measures during Omicron waves, just as we can study earlier waves. But how confident would you be that we'll see the same again for a future variant? 9/9