Introduction
The most effective and practical strategy for maintaining the health of elderly individuals against infectious diseases is prevention through vaccination. Despite the production of numerous vaccines worldwide and the beneficial effects of vaccination, the success of vaccination relies on public acceptance. In recent years, there has been significant advertising against vaccination by various groups in Iran, particularly targeting the elderly community. The vaccine attitude scale (VAX) is a short 12-item tool that measures attitudes toward vaccination. This study translates and determines the validity and reliability of the Persian version of the VAX among Iranian elderly individuals.

Methods & Materials 
This cross-sectional study aimed at validating and psychometrically assessing the scale was conducted on 240 Persian-speaking elderly individuals visiting health centers in Abadan County, Iran, and health stations established in 2023, using convenience sampling. The sample size for assessing reliability through test-retest and inter-rater reliability was set at 30 individuals each. The inclusion criteria included being at least 60 years old, communicating verbally and audibly, having an acceptable cognitive level (scoring 7 or higher on the abbreviated mental test), proficiency in speaking and understanding Persian, not taking medications affecting consciousness, and providing informed consent. Meanwhile, the exclusion criteria included unwillingness to continue participation after the research process began and incomplete questionnaire responses. The data were collected using demographic questionnaires, the VAX, and the COVID-19 vaccine anxiety scale (Co-VASA) scale for adult attitudes toward the COVID-19 vaccine. The data were analyzed using the Cronbach α coefficient, confirmatory factor analysis, content validity index (CVI), and face validity index using the SPSS software, version 22, and AMOS software, version 22.

Results 
 The mean age of the elderly participants was 67 years, with 61.3% being male. The standard deviation for age was reported as 8.06 for females and 6.38 for males. The face and content validity of the questionnaire were confirmed, and the translated version of the tool included 12 items. In qualitative face validity, modifications based on feedback from the target group (elderly) were made to 5 items, and to facilitate responses, the Likert scale was changed from a 6-point to a 5-point scale to include a neutral option. In quantitative face validity, all items received a face validity index score above 0.8 and were retained for further analysis. In content validity, the CVI was calculated based on the Waltz and Basel formula, with all items receiving a CVI score above 0.8, thus confirming their retention. Convergent validity between the VAX questionnaire and Co-VASA was reported with a Spearman correlation coefficient of -0.78. Confirmatory factor analysis indicated that the four factors proposed by the tool’s creator were confirmed, and the resulting model fit was adequate. Meanwhile, reliability was calculated using the Cronbach α coefficient, internal consistency, and inter-rater reliability as 0.89, 0.9, and 0.71, respectively.

Conclusion
VAX measures individuals’ attitudes towards vaccination through 12 items. During face validity assessment, to facilitate response options, the response scale was changed from a 6-point to a 5-point Likert scale to allow for a neutral midpoint. The calculated CVI for each item indicates that these items can effectively measure elderly individuals’ attitudes toward vaccination. The correlation between the VAX and Co-VASA was calculated at -0.78. The results from confirmatory factor analysis testing the structural model proposed by the tool’s creator showed that the tool has a four-factor structure, each containing three items. The Cronbach's alpha and test-retest reliability reported in this study are at an excellent level, and the calculated kappa coefficient is considered good and acceptable.

Ethical Considerations
Compliance with ethical guidelines
This study was approved by Ethics Committee of University of Social Welfare and Rehabilitation Sciences, Tehran, Iran (Code:IR.USWR.REC.1402.046). 

Funding
This study is the result of Nastaran Talavari's master's thesis in the field of geriatric health, Faculty of Social Health, University of Social Welfare and Rehabilitation Sciences. This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors.

Authors' contributions
All authors contributed equally to the conception and design of the study, data collection and analysis, interpretation of the results, and drafting of the manuscript. Each author approved the final version of the manuscript for submission.

Conflicts of interest
The authors declared no conflict of interest.

Acknowledgments
We would like to thank the elderly participants in the study, as well as the respected colleagues at Abadan University of Medical Sciences and Health Services who helped the research team in some way in conducting this study.

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