Abstract
This study evaluates the efficacy of social media influencer endorsements for COVID-19-prevention public service announcements (PSAs) on Instagram and its underlying mechanisms. An online experiment (N = 239) tested how influencer tier (mega-influencer versus nano-influencer) and message construal (independent versus interdependent versus collective) of the PSA influenced individuals' attitudes toward the PSA and their behavioral intentions regarding COVID-19 prevention. Participants perceived mega-influencers and nano-influencers to possess similar expertise, trustworthiness, and attractiveness. However, participants regarded nano-influencers to possess greater homophily than mega-influencers. Participants exposed to a nano-influencer's PSA displayed greater intention to engage in COVID-19 prevention behaviors than those exposed to a mega-influencer's PSA. Participants' perceived homophily with the nano-influencer also mediated its effect on participants' attitudes toward the PSA and behavioral intentions regarding COVID-19 prevention. In addition, participants evaluated the PSA with collective message construal more favorably than the PSA with independent message construal. Theoretical contributions, managerial implications, and directions for future research are provided.