Vaccination uptake SMS + appointment scheduling

What we already know

Generic vaccination-information SMS produces precisely-estimated null effects (see Rhode Island COVID booster trial, 700k recipients). What does work is reminder + actionable scheduling: an SMS that includes a specific appointment the recipient can confirm without phoning the clinic moves uptake by 5–15 percentage points across multiple replications.

Hypothesis

Eligible recipients who receive an SMS with a pre-scheduled appointment will be 5–10 percentage points more likely to complete the vaccination within 60 days than recipients who receive a generic SMS reminder.

Intervention

Three-arm design: (1) no contact (control), (2) generic reminder SMS ('You are eligible for X vaccine; visit our clinic'), (3) reminder + pre-scheduled appointment ('Your appointment is reserved for Tuesday 4pm. Reply YES to confirm, CHANGE to reschedule, NO to decline').

Comparison / control

No SMS contact. Standard clinic outreach (if any) continues as usual.

Outcomes

Primary

Vaccination completion within 60 days of the intervention (binary).

Secondary

• Appointment confirmation rate
• Show rate among confirmed appointments
• Subsequent vaccination uptake (within 1 year)

Required sample size

Computed for α = 0.05, 80% power, balanced allocation. Pick the row whose baseline best matches your jurisdiction, then size at the MDE you can defend.

Need a custom value? Use the sample-size calculator.

Randomization

1. Identify the eligible-but-not-yet-vaccinated population from clinic / health-plan records.
2. Stratify by age band, primary language, and prior vaccination history.
3. Randomize 1:1:1 within each stratum.
4. Time appointments to spread across clinic hours so no single slot is oversubscribed.

Data collection

1. Vaccination outcomes from clinic / health-plan immunization records at 30, 60, and 365 days.
2. SMS engagement logs (sent, delivered, confirmed, changed, declined).
3. Show / no-show at appointment.

IRB / ethics

Public-health intervention research with minimal risk is usually exempt or expedited review. The intervention provides information and an appointment; recipients can opt out at any step. Consult your IRB and ensure compliance with HIPAA / equivalent privacy law when joining SMS records to clinical outcomes.

Common pitfalls

• Phone number quality varies dramatically by population. Validate before launch; report bounce rates.
• Language: localize the SMS for the dominant non-English languages in your population. Translation matters for effect size.
• Clinic capacity: pre-scheduling can flood appointments. Coordinate with clinic operations before launch.

Anchor evidence — registry entries this template draws from

• Vaccination Reminders and Incentives — India

  J-PAL / Seva Mandir · Rajasthan, India · 2010 · Effect: Control: 6% fully immunized; reliable schedule only: 17%; schedule plus lentil incentive: 38%

• SMS Reminders for Childhood Vaccination — Meta-Analysis

  Systematic review (international) · Global (multiple countries) · 2024 · Effect: RR = 1.11 (95% CI: 1.05–1.17); effect consistent across income settings

• COVID-19 Vaccination SMS Reminders

  Rhode Island Department of Health · Rhode Island, USA · 2021 · Effect: Largest effect: +0.2 pp (2.0% control vs. 2.2% best treatment arm) — statistically significant but practically small

Adopt this template

Tell us your context and we'll adapt the template to your jurisdiction and help you launch. No obligation. Small pilots are typically free.