57. Which Incentives Are Best at Boosting Vaccination, and Why?

Summary of 57. Which Incentives Are Best at Boosting Vaccination, and Why?

by Freakonomics Radio + Stitcher

36m•January 18, 2026
Listen to Episode

Overview of 57. Which Incentives Are Best at Boosting Vaccination, and Why?

This episode of No Stupid Questions (Freakonomics Radio + Stitcher) features hosts Stephen Dubner and Angela Duckworth discussing research from the Behavior Change for Good consortium on how to increase vaccine uptake (study used seasonal flu shots as a proxy for a then-future COVID vaccine). The conversation covers which text-message “nudges” worked, why a “dose reserved for you / waiting for you” message outperformed others, how to weigh nudges against larger incentives (lotteries, mandates), and practical implications for policymakers, clinicians, and public-health campaigns. The episode also includes a lighter segment about choosing superpowers (flight vs. invisibility) and what those preferences reveal.

Key takeaways

  • Simple, low-cost nudges can move vaccination behavior meaningfully — even a few percentage points is valuable when the intervention is nearly free and preserves autonomy.
  • A text telling people “a vaccine dose is reserved for you / waiting for you” increased flu vaccination by about 4.6 percentage points (from 42% → 46.6% in the cited test).
  • That phrasing likely works for multiple psychological reasons: default/ status quo bias, endowment effect, loss aversion, personalization (feeling cared for), and waste aversion.
  • Casual, humorous, or interactive text tones tended to perform worse in this study; tone matters and “funny” is not a guaranteed win.
  • Larger incentives (cash, lotteries) and mandates have trade-offs: they can increase uptake but risk signaling higher risk (possible backfire) or provoke political resistance. The best approach in crises is often “both/and”: combine nudges with stronger incentives or mandates where appropriate.
  • Practical problems often reflect two different demand issues: (a) persuasion (people unconvinced vaccines are safe/effective) and (b) follow-through (people intend to vaccinate but don’t). Solutions should address both.

Study details (Behavior Change for Good consortium)

  • Context: Experiment conducted pre-COVID using flu vaccination as the behavior to influence (as proxy for future COVID vaccine messaging).
  • Format: Randomized trials of many different text-message interventions delivered to people already interacting with medical care.
  • Best-performing message: “A vaccine dose has been reserved/waiting for you.”
  • Poor performers: Some casual or humorous messages (example cited: a dog-cat flu joke) and informal/interactive tones often underperformed.
  • Effect size: ~4.6 percentage point absolute increase in vaccination for the “reserved dose” message versus control.

Why the “reserved for you” nudge likely worked

  • Defaults/status quo: Implies the vaccine is already intended for you unless you opt out — leverages inertia.
  • Endowment/ownership: Framing the dose as “yours” gives it perceived value, increasing reluctance to “lose” it.
  • Loss aversion: Failing to claim something already designated as yours feels like a loss.
  • Personalization/caring signal: Even an automated text can feel like special attention, satisfying a desire to be personally noticed.
  • Waste aversion: People dislike seeing resources go unused; the idea that a dose would be wasted can motivate action.
  • Likely multi-causal: Effective interventions often work for several overlapping psychological reasons.

What didn’t work (and why tone matters)

  • Humor and casual tones (e.g., jokes) were poor performers in these tests — not because humor can never work, but because that specific execution failed.
  • Interactive invites (“text back to do X”) and overly informal language sometimes reduced effectiveness.
  • Lesson: test tone and content; “attention-grabbing” is insufficient — messages must align with the psychological levers you intend to pull.

Interpreting the magnitude: small change, big value

  • A ~4.6 percentage-point increase can be substantial when:
    • The intervention is near-zero marginal cost (automated text).
    • It reaches large populations (small percent × millions = many more vaccinated).
    • It preserves choice/autonomy (nudges over coercion).
  • Nudges rarely flip behavior wholesale, but they’re valuable complements to larger policies.

Bigger incentives, lotteries, and mandates — pros, cons, and evidence gaps

  • Lotteries/cash incentives: Can increase uptake; prior evidence shows lotteries can move behavior across many domains. However:
    • Potential backfire: Large payments may signal risk (people infer high payment = higher risk), per research by George Loewenstein and others.
    • Hard to evaluate quickly: State-level policies (e.g., California’s lottery) lack clean control groups, making causal inference difficult.
  • Mandates: Effective at increasing rates but politically contentious and require careful exception handling; appropriate in many institutional contexts.
  • Recommended stance: Use a mix of tools — nudges, low-cost incentives, lotteries, mandates — tailoring to local context and subgroup needs.

Practical recommendations (for policymakers, health systems, clinicians)

  • Combine approaches:
    • Use evidence-based nudges (e.g., “reserved dose”) as default outreach.
    • Offer incentives (small rewards, lotteries) where appropriate to boost motivation.
    • Apply mandates when necessary and feasible, with exceptions managed transparently.
  • Address both persuasion and follow-through:
    • Persuasion: targeted information campaigns, trusted messengers, community engagement to combat misinformation.
    • Follow-through: reduce friction (easy scheduling, walk-ins), reminders, onsite offers when patients already at medical appointments.
  • Personalize and signal care: even automated messages should feel personal; that signal of attention matters.
  • Improve clinic workflows: free clinicians from clerical burdens (data-entry assistants) to strengthen patient-facing interactions and possibly reduce barriers like “white-coat” effects.
  • Test and measure: deploy randomized trials when possible to estimate causal impacts of new incentives or message framings.

Doctor–patient interaction and system design (side discussion)

  • Current clinic architecture (doctors facing screens, turning away from patients) may undermine perceived caring and communication.
  • Simple operational changes (screen positioning, projecting patient name, hiring nonclinical data-entry staff) could improve perceived personalization and clinician satisfaction.
  • Addressing clerical workload could reduce burnout and improve quality of care.

Superpower segment (brief)

  • The hosts debate flight vs. invisibility and use the question as a projective test revealing values/preferences.
  • Angela warns invisibility can tempt immoral behavior (Ring of Gyges, Plato); Stephen considers flying less appealing because airplanes exist — he’d prefer teleportation.
  • Surveys vary: some show flight more popular; others place healing or telepathy high on preferences; choice patterns can reflect pro-social vs. self-serving inclinations.
  • Takeaway: such hypotheticals can reveal priorities (thrill, utility, prosociality, temptation) but are noisy and projective.

Fact-check highlights (from episode’s fact-check segment)

  • White-coat hypertension: 15–30% of patients with elevated office BP may have office-only hypertension; masked hypertension also exists (8–20% untreated adults; up to 61% treated adults).
  • Philadelphia initiative: Since recording, Behavior Change for Good launched a Philadelphia vaccination incentive program (36 vaccinated Philadelphians winning cash up to $50,000; ~ $400k total).
  • Superhero healing powers: Several comic/anime characters have healing/self-healing or healing-others abilities (e.g., Wolverine, Hulk, Deadpool, Elixir, Archangel, Sailor Moon).
  • Ring of Gyges: In Plato’s Republic an ancestor of Gyges finds a ring that grants invisibility, uses it to seduce the queen and seize the kingdom — classical example that invisibility leads to immoral behavior.

Notable quotes

  • “Defaults are enormously powerful.” — Angela Duckworth (explaining mechanisms behind the “reserved for you” message).
  • “Both/and, not either/or.” — Angela Duckworth (advocating combined use of nudges and stronger incentives/mandates in crises).
  • “If you can do it at almost zero cost and nobody’s harmed, it’s…a huge and important effect.” — on the value of small nudges.

Actionable checklist (quick)

  • For vaccine campaigns:
    • Use “dose reserved for you / waiting for you” style texts as part of outreach.
    • Pair nudges with low-cost incentives or lotteries, and mandates where appropriate.
    • Reduce friction for follow-through (easy access, onsite offers, scheduling help).
    • Personalize messages to signal care; avoid casual humor unless tested.
    • Run RCTs or phased rollouts to measure effects where feasible.
    • Improve clinic workflow to allow clinicians to face patients and provide personalized care.

This summary captures the episode’s main evidence, interpretation, policy implications, and memorable side discussions. For references mentioned in the show, see the episode notes at Freakonomics.com/nsq.