Identifying factors associated with acceptance of the fourth COVID-19 vaccine dose: A multicentre cross-sectional study in Indonesia

Although the World Health Organization declared the end of COVID-19 as a global health emergency in May 2023, COVID-19 remains a public health concern due to continued transmission, variants, and waning immunity. However, the number of individuals who have received a complete series of COVID-19 vaccinations in developing countries, such as Indonesia, is still limited. This study aimed to explore the factors influencing the acceptance of the fourth dose of the COVID-19 vaccine in Indonesia. A multicentre cross-sectional study using an online questionnaire was conducted from June to September 2023 among the Indonesian population aged 18 years and older. The validated self-administered questionnaire consists of three parts: sociodemographic variables, clinical history, and domains of the Health Belief Model (perceived severity, perceived susceptibility, perceived clinical barriers, perceived barriers to access to booster vaccination and perceived benefits of booster vaccine). Multivariate logistic regression was employed to estimate adjusted odds ratios (ORs) and 95% confidence intervals (CI) for each independent variable influencing the acceptance of the fourth dose of the COVID-19 vaccine. Of 1850 eligible participants, only 11% had received the fourth dose of the COVID-19 vaccine. The independent determinants of the acceptance of the fourth dose of the COVID-19 vaccine were as follows: age groups 26–35 years (OR: 1.73, 95%CI: 1.00–3.01), 36–45 years (OR: 2.65, 95%CI: 1.35–5.21), and over 45 years (OR: 3.68, 95%CI: 2.05–6.63); working as a healthcare worker (OR: 2.03, 95%CI: 1.11–3.69); having a chronic disease (OR: 1.71, 95%CI: 1.07–2.73), history of COVID-19 infection (OR: 1.64, 95%CI: 1.12–2.41), perceived susceptibility to COVID-19 (OR: 1.31, 95%CI: 1.09–1.57) and perceived benefits of the booster vaccine (OR: 1.27, 95%CI: 1.04–1.56). The acceptance of the fourth COVID-19 vaccine booster in Indonesia remained low, despite substantial evidence demonstrating its effectiveness and safety, particularly in protecting vulnerable populations. Vaccine coverage could be improved by campaigns based on key determinants of acceptance such as age, chronic disease, COVID-19 infection history and perceptions of vulnerability to infection and benefits of the vaccine.