When do people believe, check, and share health rumors on social media? Effects of evidence type, health literacy, and health knowledge.

Vaccine rumors on social media endanger public health. This study examined how evidence types influenced perceived persuasiveness and relevance and engagement intentions of vaccine rumors. We conducted a 2 (evidence type: anecdotes vs. anecdotal statistics) × 2 (stance: pro-vaccine rumor vs. anti-vaccine rumor) online experiment ( = 551) and surveyed participants' health literacy and vaccine knowledge. Anecdotal statistics were perceived as more relevant than anecdotes and indirectly influenced perceived persuasiveness and behavior intentions. This finding was confirmed when vaccine rumors were pro-attitudinal. Health literacy positively predicted perceived persuasiveness; health knowledge negatively predicted relevance and behavior intentions. Practical implications and future research directions are discussed.