As I assess potential New Year's Eve plans with the intent of spending several days indoors immediately thereafter with my parents (early-to-mid 60s, one has mild-to-moderate asthma but probably healthier than your average 60 year old otherwise ), I've been struggling to figure out how to use microCOVID.org given Omicron, boosters, and potential rapid testing.
Here are my working assumptions for everything but testing:
For rapid tests, I plan to multiply by a factor of 30% based on Tornus' post citing a 75% reduction in risk from a BinaxNOW test. I cut it down by 5 percentage points arbitrarily to reflect some uncertainty around how sensitivity varies for omicron. Uncertainty comes from the following:
- Preliminary results from the NIH: https://www.politico.com/news/2021/12/28/fda-antigen-tests-reduced-sensitivity-omicron-526217?fbclid=IwAR22ulLUhteXrFdhFiuYMLa35Ha1BXFNT_z4QlA6f6ql3nSO8tQ2Q7_WfoU
- Michael Mina explains this means "ALL tests will falter on day 1" (not that rapid antigen tests are uniquely bad), but I imagine that doesn't change the fact that rapid tests are less accurate for Omicron?). He notes that UK Gov found no impact on sensitivity for Omicron, but it seems like a lot of tests in the UK recommend throat swabbing, and that could impact accuracy for Omicron for tests like BinaxNOW which are nasal only)
- This: https://www.businessinsider.com/how-to-trust-rapid-covid-test-result-2021-12?amp&fbclid=IwAR3pio-S_xkw4uUOL07sy1lYTapjOBGzRm1iHg0Pe0GFL5aJ1NUXpYfmCGs
 In practice, I plan to navigate this by doing rapid tests every day I am with my parents, and masking indoors with a KN95 for at least the first day. Still figuring out how risky a gathering I am willing to attend given that (hang out with a few people indoors with rapid tests beforehand? Plus masks?).
If you are vaccinated, disregard any advantage microcovid gives to vaccination status. Then adjust all microcovid estimates upward by about 50%. This should give you a risk estimate consistant with new omicron data.