Ye more booster shots for all... Israel are talking about their 4th already... Really effective aren't they
I am not sure how long flu vaccines last, but they prevent you from getting a bad flu through the flu season which is usually around Winter months, but I know I get a flu vaccine every year.
Likewise Covid vaccine effectiveness probably doesn't last over a year either. I am expecting it to be a every year thing just like a flu vaccine.
In saying this USA and Israel have jumped on the vaccine train way earlier than Australia and people have been vaccinated for a longer time in both those countries.