https://www.fda.gov/media/155050/download section 5.3 says "Because nirmatrelvir is co-administered with ritonavir, there may be a risk of HIV-1 developing resistance to HIV protease inhibitors in individuals with uncontrolled or undiagnosed HIV-1 infection"

HIV protease inhibitors slow the progress of HIV to aids. So it its probably not the best thing to take if you've had the vax.... 100$ says they'll use it for to treat vaccine "breakthrough infections".