Vaccination Nudges Project: Behavioural Nudges From Pharmacists to Increase Influenza and Travel Vaccination Uptake: A Pragmatic Randomized Control Trial.

Study Population Setting This research project will take place in Alberta, Canada and in partnership with Mint Health and Drugs (Mint Pharmacy), an Alberta-based pharmacy corporation. Participants will be recruited through Mint Pharmacy patient records.

Inclusion Criteria 18 years of age and older by September 1, 2025, and visited a Mint Pharmacy site within 1 year of September 1, 2025.

Study Procedures Sampling Size and Strategy Mint Pharmacy will be sending a letter to all active clients (defined as an adult who filled a prescription at their pharmacy in the last year). The investigators estimate this will be 20,000 clients with 10,000 receiving the influenza vaccine nudge and 10,000 receiving the travel vaccine nudge. This population size will allow the investigators to detect an absolute difference of 2% between the two groups with 80% power and α= 0.05.

Recruitment and Screening Mint Pharmacy analysts will pull the study sample from their patient records, including first and last name, date of birth, and sex. The list of participants will be shared with Alberta Strategy for Patient Oriented Research (AbSPOR) analysts for randomization and data linkage. AbSPOR analysts will share the randomized list of participants, including mailing addresses, with the approved mail vendor to print and mail the appropriate nudge letter that the participant has been randomized to receive. The investigators will stratify be geographic zone (North, Edmonton, Central, Calgary, and South) because of the geographic variation in vaccine uptake.

Intervention The Alberta Government provides free influenza vaccines from October through March annually, which corresponds with peak travel vaccine season. Travel vaccines are typically low cost or covered by private insurance. Vaccines are frequently administered by pharmacists in private pharmacies. As a pragmatic trial, there will be no in-person encounters with patients during the trial. The intervention will be delivered through mailed letters with different messages described below, to be delivered in mid-October 2025. The date of the initial letter will be defined as study baseline.