I know of one other study (can't find it at the moment though) that specifically looked not for CT value but if they are able to infect cells. The outcome was something like vaccinated people do replicate virus, but the spikes of those viruses are (mostly) deactivated by antibodies and therefore not as infectious as virus obtained from unvaccinated people. In rt-PCR tests you can't really distinguish infectious from deactivated virus.
I know of one other study (can't find it at the moment though) that specifically looked not for CT value but if they are able to infect cells. The outcome was something like vaccinated people do replicate virus, but the spikes of those viruses are (mostly) deactivated by antibodies and therefore not as infectious as virus obtained from unvaccinated people. In rt-PCR tests you can't really distinguish infectious from deactivated virus.