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Synthesis

What we know about increasing vaccination uptake

From SMS reminders to small incentives to default scheduling — what raises vaccination rates and what produces precisely-estimated zeros.

4 experiments synthesized · 3 positive, 0 mixed, 1 null, 0 negative

Vaccination is unusual among behavioral targets in that the outcome is binary, easy to measure, and the action required is brief. That makes it one of the most rigorously studied behaviors in public health — and one where the gap between theory and evidence is largest. Many interventions that 'should' work do not, and the magnitude of effects from those that do is modest.

The clearest pattern is that interventions which remove a logistical barrier (reminder + appointment, default scheduling, mobile vaccination units) produce reliable 5–15 percentage point gains. Interventions that aim to change minds at the point of decision — informational campaigns, generic reminders without an action — typically produce precisely-estimated zeros.

The Rhode Island COVID booster SMS trial, with 700,000 recipients and a precisely null result, is one of the most informative null findings in recent public health. It is also a model for how agencies should handle interventions that don't work: run them honestly, report the null, save the next million dollars.

Takeaway

Treat any vaccination intervention claim with the prior that 'reminder + appointment' moves the needle and 'message campaign' does not — and run a small pilot before scaling either.

The underlying experiments

Positive findings

3 experiments

Null findings

1 experiment

Related policy areas

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