My 40-liter backpack travel guide
https://vitalik.ca/general/2022/06/20/backpack.html

“...and covid defense gear: a CO2 meter (CO2 concentration minus 420 roughly gives you how much human-breathed-out air you're breathing in, so it's a good proxy for virus risk), masks, antigen tests and fluvoxamine.”

I am so unsurprised that Vitalik keeps a bunch of covid paranoia in his travel backpack.