The question of COVID-19 immunity is one that is currently being studied by researchers. Immunity can include natural immunity and vaccine-induced immunity. While some believe that having had COVID protects you from contracting the virus again, it is possible to have COVID multiple times. "There is not enough information currently available to say if or for how long after infection someone is protected from getting COVID-19 again. This is called natural immunity. Early evidence suggests natural immunity from COVID-19 may not last very long, but more studies are needed to better understand this" (Mayo Clinic).
"New studies show that natural immunity to the coronavirus weakens (wanes) over time, and does so faster than immunity provided by COVID-19 vaccination" (John Hopkins). Information from the CDC states, "Current evidence suggests that reinfection with the virus that causes COVID-19 is uncommon in the 90 days after initial infection" (CDC). However, some studies show that protection can last up to eight months (NIH Research).