This is simply incorrect, although I don't blame you for thinking so since there were some sensationalist news articles tripping over themselves to imply that it was the case.

Rates of COVID reinfection remain vanishingly small.

Experts say active immunity likely lasts for years. Antibodies drop off potentially quickly but that’s not a big deal if you have active immunity.

Mind to share sources about the immunity lasting only 3 months?

From what I read, Corona-virii are in general slow to mutate and infected people should be immune for a longer time. Also, not to sound like a conspiracy theorist, but this idea that a vaccine should neatly work in a way that it would be recommended to take it on every season smells of a pharma PR submarine.

It comes from a misunderstanding: antibodies last around that long, but so far no one's T-Cells have stopped reacting to the virus. Immunity lasting only as long as the antibodies is also how I understood it to work until mid-summer.

Yeah, I remember an article from October claiming only 5 cases of reinfection. To me these are more likely to have happened due to the people having compromised immune systems than to some specific property of the novel corona.