The WHO would prefer you not to take the vaccine if you are at low risk. While not a personal medical argument it's still in good faith. I am being cheeky by extending their booster logic to the whole vaccine - the WHO are probably thinking it but too ashamed to say it out loud.
There are multiple vaccines too! The Australian regulator recommends against some vaccines for the young and up until recently they were the only ones available.
https://www.cnbc.com/2021/09/21/who-repeats-warning-against-...
There are multiple vaccines too! The Australian regulator recommends against some vaccines for the young and up until recently they were the only ones available.
https://www.health.gov.au/initiatives-and-programs/covid-19-...
I'm sure there are plenty of other reasons - God forbid you might even have a religious objection to vaccines.