Immunity is likely long term. There was evidence of a bone marrow compartment formation after primary infection in the early days of the pandemic, maybe even as early as 2020. It continues to be supported.
Latest: https://jamanetwork.com/journals/jamanetworkopen/fullarticle...
"This work provides further evidence of sustained immune response in children up to 1 year after primary SARS-CoV-2 infection."
More details on the mechanism: https://pubmed.ncbi.nlm.nih.gov/34030176 "Overall, our results indicate that mild infection with SARS-CoV-2 induces robust antigen-specific, long-lived humoral immune memory in humans."
Follow the science. There is no need to panic.