What are you talking about? As far as we can determine, HCoV-OC43 did cause a global, multi-year long pandemic starting in 1889.
e.g. https://www.channelnewsasia.com/commentary/covid-omicron-var...
>Do the unvaccinated populations fuel the emergence of SARS-CoV-2 variants?
> The consensus among the scientific community is yes, they likely do. Unvaccinated people have less protection from the SARS-CoV-2 virus and thus would allow more of the virus to multiply within them.
> The higher rate of virus multiplication in the unvaccinated is likely to result in more possible mutations of the virus, resulting in the emergence of a larger number of variants in unvaccinated than vaccinated people.
I think at this point there is not much more to say here, at least from my end. Have a great day.