Question: Since the period from transmission to infection is shorter for Omicron, does that mean we should be testing sooner after exposure (like 2-3 days)?
Answer: CDC recommends testing 5 days after exposure (see Q&A of 1/6). Meanwhile, research indicates that the median incubation period for Omicron is 3 days (Figure). Since the time from exposure to symptoms is so short with Omicron, one would make the logical leap that we should be testing sooner. Given current testing limitations, I’m not keen to make that leap unless a person is experiencing symptoms (in which case, they should definitely test ASAP). So, why my reticence? It’s because of two things:
- A high likelihood of false negatives with rapid antigen tests during the course of early infection coupled with still limited availability/accessibility of rapid tests.
- Caveat: if we had widely available, inexpensive, and easily accessible rapid tests, I’d suggest testing early and often post-exposure (e.g. daily beginning on day 2 after exposure through day 5 or 6) while continuing to follow other quarantine guidelines.
- Limited availability and timeliness of PCR tests.
- Caveat: PCR tests are far more sensitive than rapid antigen tests, and are able to pick up traces of the virus early in the course of infection. If an individual has easy access to PCR testing, and can be assured that results will be returned quickly (e.g. <24 hours), then it might be worth pursuing.
Figure. Testing (from NY Times)
