Table S1. Hesitancy to receive COVID-19 vaccine booster doses and descriptive statistics of independent variables of interest (among 525 participants who completed the primary vaccination series).
| Hesitancy to receive COVID-19 vaccine booster doses and individual-level variables | No. of participants | Percentage (%) |
| Abbreviation: COVID-19=coronavirus disease 2019; SD=standard deviation. * Positive Attitude Scale. 3 items. Cronbach’s alpha: 0.90. Exploratory factor analysis identified one factor, explaining 83.38% of total variance. † Negative Attitude Scale. 5 items. Cronbach’s alpha: 0.84. Exploratory factor analysis identified one factor, explaining 72.05% of total variance. § Media Exposure Scale, 4 items, Cronbach’s alpha: 0.90, one factor was identified by exploratory factor analysis, explaining 76.39% of total variance. | ||
| Hesitancy to receive COVID-19 vaccine booster doses | ||
| Uptake of the first COVID-19 vaccine booster dose (the third dose) | ||
| No | 263 | 50.1 |
| Yes | 262 | 49.9 |
| Behavioral intention to receive the first COVID-19 vaccine booster dose (among participants who had not received it, n=263) | ||
| Likelihood of outcomes: unlikely to neutral | 168 | 63.9 |
| Highly probable | 95 | 36.1 |
| Hesitancy to receive the first COVID-19 vaccine booster dose (the third dose) | ||
| No | 357 | 68.0 |
| Yes | 168 | 32.0 |
| Hesitancy to receive the second COVID-19 vaccine booster dose (the fourth dose) | ||
| No | 229 | 43.6 |
| Yes | 296 | 56.4 |
| Individual-level variables | ||
| Positive attitudes toward COVID-19 vaccine booster dose, n (%) agree/strongly agree | ||
| Receiving a booster dose can maintain your antibody level and strengthen the protection against COVID-19 | 289 | 51.2 |
| A booster dose is highly effective in protecting you from COVID-19 variants of concern (e.g., Omicron) | 190 | 36.2 |
| A booster dose is highly effective in preventing severe consequences of COVID-19 | 253 | 48.2 |
| Positive attitude scale*, Mean (SD) | 10.8 | (2.1) |
| Negative attitudes toward COVID-19 vaccine booster dose, n (%) agree/strongly agree | ||
| The protection offered by COVID-19 vaccine booster dose is weaker among people with cancers | 184 | 35.0 |
| Cancer therapy would reduce the protection of COVID-19 vaccine booster dose | 167 | 31.8 |
| The side effects of COVID-19 vaccine booster dose are more severe among people with cancers | 195 | 37.1 |
| The duration of protection of COVID-19 vaccine booster dose is shorter among people with cancers | 101 | 19.2 |
| COVID-19 vaccine booster dose would negatively affect the control of cancers | 191 | 36.4 |
| Negative attitude scale†, Mean (SD) | 16.1 | (4.0) |
| Perceived subjective norm related to COVID-19 vaccine booster dose, n (%), agree/strongly agree | ||
| People who are important to you, such as family members or healthcare providers, would likely support you in receiving a booster dose | 190 | 36.2 |
| Item score, Mean (SD) | 3.2 | (0.9) |
| Perceived behavioral control to receive a COVID-19 vaccine booster dose, agree/strongly agree | ||
| Receiving a COVID-19 vaccine booster dose is easy for you if you want to | 253 | 48.2 |
| Item score, Mean (SD) | 3.4 | (0.9) |
| Vaccination fatigue: n (%) agree/strongly agree | ||
| You are tired of receiving COVID-19 vaccination over and over again | 90 | 17.1 |
| Item score, Mean (SD) | 2.5 | (1.3) |
| Media influences related to COVID-19 and COVID-19 vaccination | ||
| Frequency of exposure to the following contents on TV, radio, newspaper, and internet, n (%) sometimes/always | ||
| Infectivity of the Omicron variant of COVID-19 | 407 | 77.5 |
| Risk of having severe consequences or death is relatively low following infection of the Omicron variant of COVID-19 | 341 | 65.0 |
| COVID-19 pandemic is not under control after COVID-19 vaccination rollout | 283 | 53.9 |
| Some people contract COVID-19 after completion of their primary vaccine series | 314 | 59.8 |
| Media exposure scale§, Mean (SD) | 11.1 | (3.4) |
| Frequency of thoughtful consideration about veracity of COVID-19-specific information | ||
| Almost never | 102 | 19.4 |
| Seldom | 108 | 20.6 |
| Sometimes | 206 | 39.2 |
| Always | 109 | 20.8 |
| Item score, Mean (SD) | 2.6 | (1.0) |