SARS CoV-2 reinfection rate is higher in the Omicron variant than in the Alpha and Delta variants

BACKGROUND AND OBJECTIVES: Many mutations in variants for instance Delta and Alpha are associated with immune evasion and higher infectious potential. There are uncertainties regarding Omicron. In this regard, we aimed to compare the frequency of reinfection of SARS CoV-2 variants in our hospital between April 22, 2021 and January 26, 2022. METHOD: The reinfection rates and demographic characteristics of a total of 27,487 COVID-19 patients infected with different SARS CoV-2 variants were examined. RESULTS: Reinfection was found in 26 (0.46%) of 5554 Alpha, 209 (1.16%) of 17,941 Delta, and 520 (13.0%) of 3992 Omicron variants. A statistically significant difference was observed between the reinfection rates of the variants (p = 0.000). The mean reinfection days were calculated as 204.4 ± 51.1 in the Alpha variant, 291.2 ± 58.2 in the Delta variant, and 361.2 ± 131.6 in the Omicron variant (p = 0.000). It was observed that 16.5% of reinfection cases caught COVID-19 for the second time 3–6 months after the first COVID-19 infection, 36.7% after 6–12 months, and 46.8% after more than 12 months. There was a significant difference between the times in reinfection cases. Most reinfections occurred more than 12 months apart. Among those with a reinfection time > 12 months, 0% had Alpha, 3.4% had Delta, and 96.6% had Omicron variants. CONCLUSION: The highest reinfection rate was observed in the Omicron variant. Reinfection was approximately 30 times more frequent in the Omicron variant than in the Alpha variant and 10 times more frequent in the Delta variant.