What are these other vaccines? are the vaccinations for other coronaviruses? I'm not a biologist so I'm not seeing the connection. Is there reason to believe adding more doses would make the prevention jump from less than a year to a decade?
https://www.cdc.gov/vaccines/schedules/hcp/imz/child-adolesc...
The flu, for example as existed longer than COVID and we do not have a "3 dose" vaccine that prevents the flu for a decade. Why would we expect this for COVID as opposed to an annual booster?