Objective To explore the characteristics of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) reinfections caused by Omicron variant for providing a reference to the containment of SARS-CoV-2 reinfection.
Methods From China Information System for Disease Control and Prevention, we extracted 2 567 registered cases of 5 local coronavirus disease 2019 (COVID-19) epidemics in Chengdu city from February to September, 2022. Telephone follow-up surveys were conducted among the cases and their family members to collect the information on demographic characteristics, clinical symptoms, and viral nucleic acid or antigen tests in previous one month. The information on participants' COVID-19 vaccination were extracted from Immunization Program Information Management System of Sichuan Province. Data analyses were performed with SPSS 19.0.
Results For the 2 263 eligible respondents (88.16% of all the participants), 44.68% were male and 55.32% were female; the ages of the respondents ranged from one month to 90 years, with the mean age of 34.88 ± 19.22 years; the majority (61.82%) of the respondents were mild cases and 31.64% were asymptomatic cases; 55.86% and 29.56% of the respondents reported having been vaccinated with 3 and 2 doses of COVID-19 vaccine. Based on genome sequencing on virus strains isolated from the cases of the 5 local epidemics, the most (98.89%) of the sufferers of the 5 epidemics were infected with Omicron subvariant BA.2. Among all the eligible respondents, 197 (8.71%) reported COVID-19 reinfection appearing during November – December, 2022 – an epidemic period with Omicron subvariant BA.5.2 being the most prevalent strain in local region and there was no reinfection case being reported before the period, and the self-reported median interval from previous infection to the reinfection was 98 (25th percentile: 93, 75th percentile: 104) days. For the 197 reinfections, 193 (97.97%) reported clinic symptoms including fever, throat ache and headache; 113 (57.36%) reported only having self-medication; more reinfections were reported by the respondents without COVID-19 vaccination compared to the respondents with 3 or 2 doses of COVID-19 vaccine.
Conclusion The survey results suggest that Omicron variant-related SARS-CoV-2 reinfection is relatively low but the most of the reinfections are symptomatic. More researches and control measures on are needed for the control of SARS-CoV-2 reinfection.
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