Why make assumptions that make you look stupid.
Firstly it's not a matter of "as the proportion of vaccinated individuals grows" as in Australia we are above 80% fully vaxxed in the main population areas. It's no longer a guessing game needing studies of how the virus 'might act', the actual data is flowing in and the actual data proves the vaccine reduces not only severity, death rate and hospitalisations, but also reduces spread significantly. Actual data from the US and UK suggest that spread is curbed in vaccinated populations by as much as 80% - 90%. The vast majority of spread in those countries is non-vaccinated populations, which given the low cohort numbers of these shows how virulent Covid is without vaccination.
Studying viral loads and such is a predictive measure, we are now at the stage where we can observe. And the observations are stark and clear cut.