Evidence of SARS-CoV-2 reinfection: analysis of 35,000 subjects and overview of systematic reviews

Background Reinfection by SARS-CoV-2 is a rare but possible event. We evaluated the prevalence of reinfections in the Province of Modena and performed an overview of systematic reviews to summarize the current knowledge. Methods We applied big data analysis and retrospectively analysed the results of oro- or naso-pharyngeal swab results tested for molecular research of viral RNA of SARS-CoV-2 between 1 January 2021 and 30 June 2021 at a single center. We selected individuals with samples sequence of positive, negative and then positive results. Between first and second positive result we considered a time interval of 90 days to be sure of a reinfection. We also performed a search for and evaluation of systematic reviews reporting SARS-CoV-2 reinfection rates. Main information was collected and the methodological quality of each review was assessed, according to A Measurement Tool to Assess systematic Reviews (AMSTAR). Results Initial positive results were revealed in more than 35,000 (20%) subjects; most (28%) were aged 30–49 years old. Reinfection was reported in 1,258 (3.5%); most (33%) were aged 30–49 years old. Reinfection rates according to vaccinated or non-vaccinated subjects were 0.6% vs 1.1% ( p