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: Coronavirus disease 2019 (COVID-19) outbreaks often occur in nursing homes and prompt frequent surveillance testing for SARS-CoV-2. A single dose of the BNT162b2 vaccine reduces viral load and transmission. In this study, we describe the real-world efficacy of BNT162b2 single-dose vaccination during a COVID-19 outbreak at a Veterans Affairs Community Living Center (CLC). METHODS: From 12/2/20-5/14/21, twice weekly antigen testing was used to detect COVID-19 among 146 residents at the CLC. Residents without a prior history of COVID-19 who agreed to immunization were vaccinated with the BNT162b2 vaccine on 12/16/20 and 1/6/21. Single-dose vaccine efficacy was determined for days 1-21 and days 14-21 after the first vaccine dose. RESULTS: The outbreak occurred from 12/2/20-1/7/21 with an attack rate of 30.8% (45/146); 46.7% (21/45) of the cases were due to asymptomatic COVID-19. One unit accounted for 77.8% (35/45) of the cases. In the vaccine analysis, 116 residents were a median age of 74.5 years and 93.1% (108/116) had >/= 1 comorbid condition. Between the first and second dose, 15.5% (15/97) of vaccinated residents, and 21.2% (4/19) of unvaccinated residents developed COVID-19 (p=0.81). One week after the second dose, no cases of COVID-19 occurred. CONCLUSIONS: Albeit limited by the small numbers, a single dose of the BNT162b2 vaccine was not efficacious at preventing COVID-19 during this nursing home outbreak.
["Treatment"]