HPV shot for 10yo

So my sisters doctor has suggested her giving her 10yo son the hpv shot, he’s up to date on all vaccinations, but she’s weary of this...what do u guys suggest? She said the side effects are scaring her off🤔 and idk much about it so I wanted to get some info from u smart ladies because she asked me what my opinion was and if I will get it for my daughter when the time comes.