COVID-19 Vaccination SMS Reminders
Rhode Island Department of Health · Rhode Island, USA · 2021
Summary
A statewide RCT with 700,000 participants found that SMS nudges had vanishingly small effects on COVID vaccination. The absolute difference between the best and worst message was 0.2 percentage points. The study is an important corrective: the power of nudges is context-dependent, and when the primary barrier is not awareness or forgetfulness but deeper hesitancy or access constraints, SMS reminders accomplish little. The null result is as valuable as any positive finding.
Research question
"Can SMS nudges with varied message frames increase COVID-19 vaccination uptake?"
Methodology
Intervention
Multiple SMS message frames tested: loss/gain framing, social norms, personal benefit, civic duty
Assignment
Randomized controlled trial (individual)
Sample size
~700,000 Rhode Island residents
Primary outcome
COVID-19 vaccination rate within 30 days
Effect estimate
Largest effect: +0.2 pp (2.0% control vs. 2.2% best treatment arm) — statistically significant but practically small
Decision
SMS campaigns deprioritized for vaccination; insights redirected toward in-person and community-based outreach
Result
Null
Largest effect: +0.2 pp (2.0% control vs. 2.2% best treatment arm) — statistically significant but practically small
Evidence strength
Strong
Randomized trial, replicated across multiple sites or studies.
Replication status
Replicated
Institution
Rhode Island Department of Health
Location
Rhode Island, USA
Year
2021
Policy area
Public Health
Mechanism
Information