Expanding on this clinical view, and this is decidedly so for the clinical flu you see, but... while a lot of flu is sub-clinical, which you know, most are not aware of the data suggesting most flu cases may be asymptomatic.
Drs. Fragaszy's (PhD) and Hayward's (MD) works on PIPS an Flu Watch (and now Virus Watch) cohort studies out of England are worth the look. Their UCL group's work is pretty amazing not because of the annual 18% attack rate (in the unvaccinated), but that 77% of cases were asymptomatic in that study... some other works showed 25-50% and this likely varies by year/lineage (Flu Watch was looking at 2009 H1N1 vs we have H3N2 predominant this year so far). From their followup work, crossprotective T cell mediated immunity seemed to drive lower symptomatic rates. This data is key because underestimating asymptomatic cases leads to overestimating severity and missing transmissions, as we saw with early COVID data as well.
https://www.thelancet.com/journals/l...034-7/fulltext
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5837336/
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4476562/
https://discovery.ucl.ac.uk/id/eprint/10151113/
From the same peeps, I always like empirical evidence for hand hygiene applied from past datasets to speculate on the now (washing hands prevents common human coronavirus infection, will be interesting to see if Virus Watch data shows this for COVID)
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8243225/
And empirical data for eye protection with COVID
https://www.medrxiv.org/content/10.1....29.22272997v1