You are presented with a paragraph from a COVID-19 literature. Classify the topics of this piece of text by choosing from the following categories:

- Epidemic Forecasting: The content relates to predictions about the spread of COVID-19.
- Treatment: The paragraph discusses therapeutic methods or medication for COVID-19.
- Prevention: The content covers measures to prevent the spread of COVID-19.
- Mechanism: The paragraph explains the biological mechanisms of the virus.
- Case Report: The content is a report of a COVID-19 case.
- Transmission: The paragraph discusses how COVID-19 is transmitted.
- Diagnosis: The content is about diagnosing COVID-19 in individuals.

Your classification should be provided as an element within a JSON array. The array should be formatted with topics enclosed in double quotes and separated by commas, following the JSON format, for example: ["Topic1", "Topic2", ...]. Include all applicable topics within the array. Your output should be a valid JSON array, and no additional text should be included in your response.

Article:

Background: Reinfection/reactivation of SARS-CoV-2 has been a matter of great interest from the immunological and vaccine perspective. However, little is known about the clinical presentation of such reinfection/reactivation. We report a case series of 9 COVID-19 patients having experienced two clinically- and/or virologically-confirmed episodes of COVID-19. Methods: Epidemiological and clinical characteristics of 9 healthcare workers (HCWs) with two episodes of SARS-CoV-2 are described. Results: The incidence of reinfection/reactivation amongst the HCWs was 2% (9 out of 491) with an average remission period of 66 days (range 43-78 days). Amongst the cases of reinfection 4/9 were asymptomatic in first episode were symptomatic in second episode. There is negative correlation between numbers of days the patients took to become SARS-CoV-2 negative by RT-CPR and/or clinically recover in the first episode and the second episode irrespective for the time spent in remission. Conclusion: Shorter durations of SARS-COV-2 infection in the first episode are associated with longer time to recovery in the second episode in patients with re-infection/reactivation.
["Case Report"]