I guess you and I read different articles. I don’t remember ever coming across any data demonstrating fading immunity over time or reinfection on any meaningful scale.
Regarding your question, this article from Nature is hopefully useful:
With highly effective vaccines for COVID-19 approved, a critical question for informing health policy in a post-pandemic world is the maintenance of immunity against SARS-CoV-2. One year into the pandemic, a picture has emerged that immune responses generated against SARS-CoV-2 are, on average, in line with immunological predictions for this type of infection. Recent studies show that antibodies to SARS-CoV-2, including neutralizing ones, persist in the serum for at least 6–7 months following infection in 90% of subjects tested. Antibody kinetics are typical of those seen in many other infections. Levels peak 3 weeks post-symptoms with a subsequent contraction and plateau phase. Predicted from the presence of good quality antibodies, T cell responses are mounted as expected. T cells are crucial for orchestrating other components of the immune response, including B cell antibody maturation and production and the formation of long-lived memory cells.
What are the implications of these findings for a post-COVID-19 world? Will we achieve protective population-level (or ‘herd’) immunity? Will vaccinations eradicate SARS-CoV-2? Will repeat vaccinations be required to maintain immunity? We can look to our accumulated knowledge on the ecology of other human coronavirus (HCoV) infections to provide insights into these fundamental questions.