A video summary released 2nd April 2022 by Grant Dixon shows through a series of graphs how the effects of boosters have worn off rapidly in New Zealand, especially since the BA2 variant started circulating. 

Grant Dixon has been carefully following the NZ Ministry of Health Covid statistics during the last 15 months. By the start of April the rate per 100,000 of Covid hospitalisations for the boosted overtook the rate of hospitalisations for the unvaccinated. Watch the video, the magnitude of the change is very obvious.

Even prior to the pandemic, it was realised that vaccines that allow transmission could drive the evolution of more highly virulent pathogens: