Early SARS-CoV-2 reinfections within 60 days highlight the need to consider antigenic variations together with duration of immunity in defining retesting policies

The emergence of the SARS-CoV-2 Omicron variant, characterized by a significant antigenic diversity compared to the previous Delta variant, had led to a decrease in antibody efficacy in both convalescent and vaccinees’ sera resulting in high number of reinfections and breakthrough cases worldwide. However, to date, reinfections are defined by the ECDC as two positive tests ≥60 days apart, influencing retesting policies after an initial positive test in several European countries. We illustrate by a clinical case supplemental by epidemiological data that early reinfections do occur within 60 days especially in young, unvaccinated individuals. In older patient groups, unvaccinated and patients with a basic vaccination scheme are more vulnerable to reinfections compared to patients who received a first booster vaccine. For this reason, we consider that the duration of protection offered by a previous infection should be reconsidered, in particular when a shift between consecutive SARS-CoV-2 variants occurs. ### Competing Interest Statement The authors have declared no competing interest. ### Funding Statement UZ Leuven, as national reference center for respiratory pathogens, is supported by Sciensano, which is gratefully acknowledged. ### Author Declarations I confirm all relevant ethical guidelines have been followed, and any necessary IRB and/or ethics committee approvals have been obtained. Yes The details of the IRB/oversight body that provided approval or exemption for the research described are given below: The Ethics committee of University Hospitals Leuven gave ethical approval for this work. I confirm that all necessary patient/participant consent has been obtained and the appropriate institutional forms have been archived, and that any patient/participant/sample identifiers included were not known to anyone (e.g., hospital staff, patients or participants themselves) outside the research group so cannot be used to identify individuals. Yes I understand that all clinical trials and any other prospective interventional studies must be registered with an ICMJE-approved registry, such as ClinicalTrials.gov. I confirm that any such study reported in the manuscript has been registered and the trial registration ID is provided (note: if posting a prospective study registered retrospectively, please provide a statement in the trial ID field explaining why the study was not registered in advance). Yes I have followed all appropriate research reporting guidelines and uploaded the relevant EQUATOR Network research reporting checklist(s) and other pertinent material as supplementary files, if applicable. Yes All data produced in the present study are available upon reasonable request to the authors