Can anyone who has been infected with SARS-CoV-2 get the virus again? How serious is reinfection? These are two questions answered by Professor António Vaz Carneiro, a Physician specialized in Internal Medicine, Nephrology and Clinical Pharmacology and a Full Professor at FMUL, in the journal Prevenir é Saúde (Prevention is Health). The article addresses the issue of reinfection/reactivation and the duration of immunity against covid-19.