Table A1.

Question list of key variables used in this survey.

Measures	Questions	Question Design and Coding
COVID-19 booster acceptance	If a COVID-19 booster is recommended as a supplement to the current vaccination schedule, would you accept it?	Binary (“yes [1]” or “no [0]”).
	What are the reasons for accepting booster vaccination? What is the primary reason for refusing booster vaccination?	Multiple choices for question 1, and single choice for question 2.
Willingness to pay	What is the maximum amount that you are willing to pay for an annual COVID-19 booster vaccination?	Open-ended question with values.
History of COVID-19 vaccination	Have you received at least one dose of a COVID-19 vaccine so far?	Binary (“yes [1]” or “no [0]”).
Perceptions of COVID-19 infection and booster vaccination	Self-reported HBM items assessed on a five-point Likert scale, please see Table A2 for detail.	Five-point answers were converted to binary variables, e.g., agree [1] (i.e., “strongly agree” or “agree”) and neutral/disagree [0] (i.e., “neither agree nor disagree”, “disagree” or “strongly disagree”).
Sociodemographics	Which age group are you currently in?	Four age groups (18–30, 31–40, 41–50, and 51–59 years old).
	What is your gender?	Binary (“female [1]” or “male [0]”).
	What is your maternal status?	Three groups were converted to binary variables: married [1] (“married”) and never married/divorced/widowed [0] (“never married” or “divorced or widowed”).
	What is your education level?	Four groups were converted to binary variables: senior high school/technical school or below [0] (“middle school or below” or “senior high school/technical school”) and college/associate/bachelor’s degree or above [1] (“college/associate/bachelor’s degree” or “master’s degree or above”).
	What is your employment status?	Four groups were converted to binary variables: employed [1] and retired/out of work/still a student [0] (“retired”, “out of work”, or “still a student”).
	How much is your household annual income?	Three income groups (≤100,000, 100,001–200,000, and >200,000 CNY).
	Which area do you reside in?	Binary (“urban [1]” or “rural [0]”).
	Which province do you reside in?	Respondents were further categorized into living in western, central, and eastern regions based on the province they reside in.
	Rate your own overall health status.	Five-point Likert scale (“very good” to “very poor”). The answers were converted to binary variables: good [1] (“very good” or “good”) and fair/poor [0] (“fair”, “poor”, or “very poor”).
	Do you have any chronic diseases such as hypertension, diabetes, heart disease, etc.?	Binary (“yes [1]” or “no [0]”).
	Do you belong to any of the following priority groups for COVID-19 vaccination? (Health professionals, community workers, workers in the cold-chain logistics sector, customs inspectors, etc.).	Binary (“yes [1]” or “no [0]”).