"how could it" - By weakening the immune system in general ( i have no idea if it's plausible, but i've seen people saying vaccines were also having detrimenta

"how could it" - By weakening the immune system in general ( i have no idea if it's plausible, but i've seen people saying vaccines were also having detrimental side-effects for ages, even before covid) - by having the body produce facilitating antibodies once again, not saying those hypothesis are true. Only that it seems to me it's super hard to predict side-effects of anything in the fields of biology, especially when you're talking about rare occurrences.