1. Study design and data collection This class pilot study will be conducted in
September 2023 at a nursing home in Taizhou, China. This study has been approved by
the Ethics Committee of Taizhou Hospital, Zhejiang Province, China (approval number:
K20230832). All procedures will be performed in accordance with the guidelines of
our institutional ethics committee and in compliance with the Declaration of
Helsinki. The respondents' information will remain anonymous.

2. Patients and public involvement The study participants will be not involved in the
design, implementation, or reporting of the study.

2.1 Recruitment 2.2.1 Inclusion criteria

1. 60 years old or above

2. Have not been vaccinated for COVID-19 or have not completed the fourth booster shot
of the COVID-19 vaccine

3. Able to communication and willing to participate in the survey voluntarily 2.2.2
Exclusion criteria

(1) People with contraindications to vaccination (2) People with communication disorders
(3) Those who do not want to participate in the survey 2.3.3 Grouping of study
participants We will select four senior care institutions in Taizhou City with a
population of 100 or more residents. We will divide them into intervention and control
groups.

2.4 Sample size The sample size was determined using G*Power software v3.1.9.2
(Heinrich-Heine-Universität Düsseldorf, Düsseldorf, Germany). It will be estimated for
repeated measures between the two groups at a significance level of 0.05, effect size of
0.19, and power of 95%. The final calculated sample size is 182 participants. Assuming a
10% attrition rate over the course of the intervention, we set a target of recruiting 200
participants. Based on the number of repeated measurements, this represented 100
participants in each group.

2.5 Composition of investigators

1. One master's degree in public health

2. Four master's degrees in infection

3. Two physicians in infectious diseases

4. Two trained locals 2.6 Intervention 2.6.1 Control group: traditional health
education In the control group, a conventional intervention will be used, and health
education brochures on the COVID-19 vaccine will be distributed for the study
participants to read on their own time. The contents of the brochure included basic
knowledge concerning the SARS-CoV-2 coronavirus, COVID-19 vaccine, herd immunity,
and precautions for vaccination.

2.6.2 Self-determination theory-based health education measures The intervention group
received self-determination theory-based interventions, with targeted interventions
proposed based on the self-determination theory-including health-related talks and
sharing sessions. To ensure that older individuals with varying levels of literacy
understood the intervention, the process was conducted in the local native dialect.
Health lectures will be conducted to elicit and acknowledge the perspectives and emotions
of our cohort of older adults toward vaccination, support their choices and initiatives,
and provide a rationale for vaccination-related recommendations while communicating with
them to better understand their major barriers toward vaccination. This will be done with
the idea of meeting the autonomy and competence needs of our cohort, based on one of the
basic premises of self-determination theory. Health-related lectures empower older adults
to make autonomous decisions through cognitive reframing . It has been found that
successful vaccination planning relies on people acquiring appropriate and adequate
health-related knowledge. The three basic psychological needs of older adults will be met
through communication and interaction, both with them and with significant members of
their lives (e.g., caregivers, family members, doctors, and nurses) during sharing
communication sessions. We also will seek to motivate the participants by asking them
questions and awarding them gifts during each health lecture and sharing session.
Competence needs will be met by developing challenges for our participant cohort . The
entire intervention will last 6 weeks, and will be followed by a face-to-face
questionnaire.