Every single benefit of the vaccines seem to fade over six months or so - not justt symptomatic infections, but also protection against serious effects, hospitalization, and death. That's why there's been so much push for boosters even in countries like the UK which have given up on stopping the spread of the virus. (Yes, I know the WHO is opposed to booster shots, but frankly they seem to be a bunch of idiots who care more about what's politically useful than reality these days.)