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:

Objectives: This study aimed to explore the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2)-specific humoral responses and T-cell responses in patients who have recovered from coronavirus disease 2019 (COVID-19) to understand the natural protective immune responses and to facilitate the development of vaccines. Methods: We conducted a combined assessment of the changes in neutralising antibody levels and SARS-CoV-2-specific T-cell responses over time in 27 patients up to 7 months after infection. Results: The neutralising antibody remained detectable in 96.3% of the patients at their second visit at about 7 months post-onset of symptoms. However, their humoral responses, including titres of the spike receptor-binding domain IgG and neutralising antibody, decreased significantly compared with those at first clinic visit. By contrast, the proportions of spike-specific CD4(+) T cells, but not CD8(+) T cells, in COVID-19 patients after recovery were persistently higher than those in healthy controls. No significant change was observed in the proportion of spike-specific CD4(+) T cells in patients who had recovered from COVID-19 within 7 months. Conclusion: The SARS-CoV-2-specific T-cell immune responses persisted, while the neutralising antibodies decayed. Further studies are needed to extend the longevity of neutralising antibodies and to evaluate whether these T cells are sufficient to protect patients from reinfection.
["Mechanism", "Treatment", "Diagnosis"]