I don't know how much the mutations have to do with it. But the Indian studies show a reinfection rate of 4.5% [1]. Apparently, it is common among the elderly [2]. Our CM is 78.

[1] https://science.thewire.in/health/icmr-defines-interval-for-...

[2] https://www.msn.com/en-us/news/world/covid-reinfection-rare-...