Binary 1

Reference (0)

Gender

Male (52.7%)

Female

Academic year (first)

First (28.9%)

≥Second

Course

Science (68.7%)

Humanities

Outcome variable: “How many times did you get infected with COVID-19?”

≥1 (31.5%)

Un-infected

COVID-19 vaccine: “How many times did you get vaccinated for COVID-19?”

≥1 dose (92.2%)

Un-vaccinated

≥2 doses (90.8%)

<2 doses

≥3 doses (66.9%)

<3 doses

Measles/rubella (MR) vaccine: “Have you got vaccinated for MR more than or equal to twice?”

Yes (72.0%)

No

Smoking: “Do you smoke?”

Yes (2.8%)

No

Persistent cough: “Do you have a persistent cough for more than two weeks?”

Yes (0.5%)

No

BMI low

BMI < 18.5 (14.2%)

BMI ≥ 18.5

BMI high

BMI ≥ 25.0 (10.0%)

BMI < 25.0

Health concerns including past history abnormalities (4 questions)

Yes (14.1%)

No (every 4 question)

Club or group activities: “Are you recently joining in club or group activities?”

Yes (40.7%)

No

Travel activities: “Is your travel activity recently high (≥twice per year)?”

Yes (58.2%)

No

Karaoke activities: “Is your karaoke activity (group) recently high (≥once per month)?”

Yes (19.8%)

No

International students: “Are you a student from abroad?”

Yes (2.4%)

No