Vaccination invitations sent by warm and competent medical professionals disclosing risks and benefits increase trust and booking intention and reduce inequalities between ethnic groups.

Objective: We aim to identify vaccination invitations that foster trust and improve vaccination uptake overall, especially among ethnic minority groups who are more at risk from coronavirus disease (COVID-19) and less likely to be vaccinated. Method: In a preregistered 4 × 4 mixed-design experiment, we manipulated how much risk–benefit information the message included within-subjects and the message source between-subjects (N = 4,038 U.K. and U.S. participants, 50% ethnic minority). Participants read four vaccine invitations that varied in vaccination risk–benefit information (randomized order): control (no information), benefits only, risk and benefit, and risk and benefit that mentions vulnerable groups. The messages were sent by one of four sources (random allocation): control (health institution), medical professional (unnamed), warm and competent medical professional (unnamed), and named warm and competent medical professional (Sanjay/Lamar). Participants assessed how much they trusted the message and how likely they would be to book their vaccination appointment. Results: Information about vaccination benefits and risks increased trust, especially among ethnic minority groups—for whom the effect replicated within each group. Trust also increased when the message was sent by a warm and competent medical professional relative to a health institution, but the importance of the source mattered less when more information was shared. Conclusions: Our research demonstrates the positive impact of outlining the benefits and disclosing the risks of COVID vaccines in vaccination invitation messages. Having a warm and competent medical professional source can also increase trust, especially where the message is limited in scope.