I thought I read or heard that Paxlovid wasn’t as effective if you had the vaccine and boosters. That it actually was more effective for those who are not vaccinated.
Maybe I misheard or misunderstood.
I don't know about that specific context, but from
https://en.wikipedia.org/wiki/Nirmatrelvir/ritonavir#History :
The primary data supporting the US Food and Drug Administration (FDA) emergency use authorization for nirmatrelvir/ritonavir are from EPIC-HR, a randomized, double-blind, placebo-controlled clinical trial studying nirmatrelvir/ritonavir for the treatment of non-hospitalized symptomatic adults with a laboratory confirmed diagnosis of SARS-CoV-2 infection. Participants were adults 18 years of age and older with a prespecified risk factor for progression to severe disease or were 60 years and older regardless of prespecified chronic medical conditions. All participants had not received a COVID-19 vaccine and had not been previously infected with COVID-19. ...
From a test design POV, excluding people who had been vaccinated or had recovered from Covid makes sense. The point of the test was to observe the effects of Paxlovid, and antibodies against Covid, whether from vaccine or recovery, could skew those observations due to the antibodies attacking SARS-CoV-2 viruses.
BUT the real-life usage is usually (>70% of US people have been at least fully vaccinated, and a significant % of people have recovered from Covid - I'm both, recovered and later vaccinated), these are recipient contexts that were not tested.