Abstract
BACKGROUND The increasing number of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) reinfections has opened a new research direction related to analyzing long-term immune response and accurately characterizing individual cases of reinfection to understand its mechanism and estimate the risk of widespread reinfection both locally and globally. This retrospective study from the Gyncentrum Genetic Laboratory in Sosnowiec, Poland aimed to evaluate reinfections from SARS-CoV-2 between April 2020 and July 2022. MATERIAL AND METHODS The study extended the previously published report on SARS-CoV-2 infection cases in Poland by analyzing 8041 reinfections diagnosed with real-time reverse transcription-polymerase chain reaction (RT-PCR) assay. Data were collected on the amount of time elapsed from the first infection to the next and, based on these data, all results were divided into several groups for statistical analysis: 0-44, 45-90, 91-200, 201-310, 311-420, and >420 (days). RESULTS The study showed that of the 8041 patients who experienced reinfection, the vast majority (5505) became reinfected more than 310 days after the original infection, even though the average time between infections was 354.3 days. Statistical analysis revealed that the risk of SARS-CoV-2 reinfection increases with time and that this relationship becomes statistically significant after the 200th day following the initial infection (p<0.01). CONCLUSIONS We have shown that acquired immunity to SARS-CoV-2 infection is relatively short-lived - it starts diminishing about 6 months after the initial positive test. Moreover, the risk of reinfection is very high more than 1 year after the initial infection.