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:

INTRODUCTION: COVID-19 pandemic has lead to lockdown of population in many countries. In Spain, the state of alarm was established from March 15 to June 20, 2020. Usually this fact decreased people's mobility and physical activity, in addition to producing or exacerbating psychological disorders. Our aim was to determine the influence that this condition had over the short-term ponderal results of patients undergoing laparoscopic vertical gastrectomy from May 2019 to May 2020. METHODS: Case-control study for comparing the percentage of excess weight lost (%EWL) and the percentage of total weight lost (%TWL) of patients that underwent a VG during the last year, so they were affected by lockdown in April and part of March 2020 (group 1), to the %EWL and %TWL of a control group (group 2), obtained from our previous series. RESULTS: The mean %EWL in group 1 is 47.37+/-18.59 and in group 2 is 51.13+/-17.59, being P=.438. Meanwhile, the mean %TWL in group 1 is 21.14+/-8.17 and in group 2 is 24.67+/-8.01, with P=.115. CONCLUSIONS: Population lockdown by COVID-19 did not get worse short-term results of vertical gastrectomy. More studies with a larger number of patients are necessary to draw firm conclusions.
["Prevention"]