Does not make that much intuitive sense to me because there are a lot of random mutations happening. If the first dose first (or first dose only) strategy reduces the size of the whole SARS-CoV-2 viriome, there will be fewer viruses and less genetic variation in total. More infections in total means more genetic diversity. More infections means that a vaccinated person will be exposed to more sources of infection, more virions, more different genomes over time, thus also increasing the likelihood of mutants able to escape the immunologic response.
Does that assume that the amount of mutations (and therefore the risk of an immune escape) is only dependent on the size of the viriome?
But isn’t it possible that the risk of an immune escape mutation in the 1-dose vaccinated population is much higher than in the rest of the population? I think if that was much higher, it could swamp the benefit of reduced overall chance for dangerous mutations occurring due to the reduced infections from vaccinating more people (as compared to 2 doses).
Not sure of any of this, just trying to think through your intuition.