METHODS: This paper covers detailed explanation on the various developmental and validation process stages of the CAB zoonotic disease questionnaire development. The development phase comprised thorough literature search, focus group discussion, expert panel assessment and review. The validation process included pre-test and pilot testing, data analysis of results, analysis of internal consistency and the development of the final version of the questionnaire. Participants selected represented main ethnicities, gender, levels of education and population type (urban/rural) in the Klang Valley area.

RESULTS: The items in the questionnaire has undergone various changes in structurally and linguistically. The final refined CAB questionnaire consists of 14 items cognitive (no items removed at pilot phase), nine items affective (one item removed at pilot phase) and five items behaviour (no items removed from pre-test phase), respectively. Reliability analysis revealed Cronbach's alpha values were 0.700 (cognitive) and 0.606 (affective) which indicated good internal consistency after item reduction.

METHODS: A randomised controlled experiment was conducted from 29 April to 7 June 2021, which coincided with the early phases of the national vaccination programme when vaccine uptake data were largely unavailable. 5784 Malaysians were randomly allocated into 14 experimental arms and exposed to one or two messages that promoted COVID-19 vaccination. Interventional messages were applied alone or in combination and compared against a control message. Outcome measures were assessed as intent to both take the vaccine and recommend it to healthy adults, the elderly, and people with pre-existing health conditions, before and after message exposure. Changes in intent were modelled and we estimated the average marginal effects based on changes in the predicted probability of responding with a positive intent for each of the four outcomes.

RESULTS: We found that persuasive communication via several of the experimented messages improved recommendation intentions to people with pre-existing health conditions, with improvements ranging from 4 to 8 percentage points. In contrast, none of the messages neither significantly improved vaccination intentions, nor recommendations to healthy adults and the elderly. Instead, we found evidence suggestive of backfiring among certain outcomes with messages using negative attribute frames, risky choice frames, and priming descriptive norms.

CONCLUSION: Message frames that briefly communicate verbatim facts and stimulate rational thinking regarding vaccine safety may be ineffective at positively influencing vaccine-hesitant individuals. Messages intended to promote recommendations of novel health interventions to people with pre-existing health conditions should incorporate safety dimensions.