I’ve been wondering about this:
Early in the pandemic, the United States had an undertesting problem. Now we are overtesting those who are immune and asymptomatic. A person with immunity to the coronavirus will fight off an infection. But during and after the person’s exposure to the virus, it’s common for a low number of virus particles to be detectable in the nose. In medicine, we call this virus a “colonizer” — a pathogen that does not cause illness or spread the illness. It’s an incidental finding. But in today’s world of routine coronavirus testing of vaccinated people, these positive tests are inflating the number of positive cases in a misleading way.[…] The Centers for Disease Control and Prevention has officially decreed that fully vaccinated people should not be tested for the coronavirus in the absence of symptoms. That’s because immunity works. Mounting evidence has demonstrated an extremely low risk of asymptomatic transmission by vaccinated people.
The piece uses the example of Israel, which has an 85% vaccination rate, where there are positive test results but both cases and hospitalizations have plummeted after the population was vaccinated.
But in communities and regions where vaccination rates are high, we should be rethinking our definition of a covid-19 “case.” When we’re dealing with a vaccinated person, what we call a “case” is often instead the detection of a virus warded off by antibody and T cell immunity. (This can be true even for the delta variant, highly transmissible though it may be.) Even dead viral particles can be detected by a PCR test. This pandemic has consistently required us to rethink the meaning of the data and shift our strategy accordingly. When it comes to immune people who are asymptomatic, it’s time for us to do it again.
This was written by two well-credentialed infectious disease specialists. The actionable suggestion in the piece is that the level of viral load be used to discriminate between “colonizer” positive results and positive tests that indicate the possibility of transmission.