There is less signal to noise when it comes to reinfections because the data is just harder to come by, but the preliminary evidence shows that reinfections do happen, but quite rarely (some numbers from a few waves of infections showed only 1 out of 150 positive results were from people who had tested positive previously). There has also been evidence that intensity of infection is correlated to post-infection immunity (i.e. if you were asymptomatic you have less immunity than if you were hospitalized)

It is reasonable to believe that having had an existing infection will boost your immunity against future infections and that both vaccines and previous infections will protect you on a diminishing basis, say, for a year or two. (based on existing covid evidence and the behavior of immunity to other coronaviruses which are common in humans which are usually very mild and referred to as a "cold")