{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,5,5]],"date-time":"2026-05-05T23:47:14Z","timestamp":1778024834026,"version":"3.51.4"},"reference-count":34,"publisher":"American Medical Association (AMA)","issue":"2","content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["JAMA Netw Open"],"abstract":"Importance<\/jats:title>Prior studies found that financial incentives have small, positive direct effects in increasing COVID-19 vaccination rates, but unmeasured social spillovers (ie, changes in outcomes among untreated individuals who are socially exposed to policy beneficiaries) may diminish the overall effect of such policies.<\/jats:p><\/jats:sec>Objective<\/jats:title>To assess the spillover effects of a COVID-19 vaccination financial incentive and assess whether incorporating estimates of spillover meaningfully affects broader evaluations of policy effectiveness.<\/jats:p><\/jats:sec>Design, Setting, and Participants<\/jats:title>This population-level, address-cluster randomized clinical trial was conducted in November 2021. Participants were all adult (aged \u226518 years) residents of Ravensburg, Germany, who were randomly assigned to the treatment or control group. One resident in each address cluster was randomly selected to be an address-cluster representative. Address-cluster representatives in the treatment group received the treatment letter; all other cohabitants at that same address received the control letter. All individuals in addresses randomly assigned to the control group were mailed a control letter. Intention-to-treat data analysis was conducted from January 2022 to May 2024.<\/jats:p><\/jats:sec>Intervention<\/jats:title>Control letters informed recipients about 7 upcoming free COVID-19 vaccination events. Treatment letters were identical to control letters, except they also offered \u20ac40 (US $41.46) for getting vaccinated at one of the events.<\/jats:p><\/jats:sec>Main Outcome and Measure<\/jats:title>Primary and booster COVID-19 vaccination uptake was observed and recorded on site during the public vaccination events. Primary vaccinations were defined as either the first dose of a 1-dose vaccine or the first or second dose of a 2-doses vaccine. Boosters were defined as any dose after primary vaccination. Three types of commonly used treatment effects were analyzed: direct, spillover, and overall.<\/jats:p><\/jats:sec>Results<\/jats:title>Among 41\u202f548 Ravensburg residents (mean [SD] age, 49.96 [19.04] years; 51.3% female), 796 (1.9%) were vaccinated at 1 of the 7 public vaccination events. The direct, spillover, and overall effects of receiving a financial incentive on primary vaccinations were all nonsignificant. For booster vaccinations, the direct effect was negative but not statistically significant (\u22120.32 percentage points [95% CI, \u22120.77 to 0.14 percentage points]; P<\/jats:italic>\u2009=\u2009.17), whereas the overall effect (\u22120.30 percentage points [95% CI, \u22120.51 to \u22120.09 percentage points]; P<\/jats:italic>\u2009=\u2009.006) was significantly negative. The spillover effect was significantly negative (\u22120.29 percentage points [95% CI, \u22120.53 to \u22120.06 percentage points]; P<\/jats:italic>\u2009=\u2009.01), but only for the first vaccination events.<\/jats:p><\/jats:sec>Conclusions and Relevance<\/jats:title>This trial found null direct effects on COVID-19 vaccination uptake and negative effects on booster uptake among individuals who did not receive but were indirectly exposed to the financial incentives. The timing of this spillover suggests that cohabitants of financial incentive recipients postponed booster vaccination, thereby undermining the potential effectiveness of this policy.<\/jats:p><\/jats:sec>Trial Registration<\/jats:title>ISRCTN identifier: ISRCTN59503725<\/jats:ext-link><\/jats:p><\/jats:sec>","DOI":"10.1001\/jamanetworkopen.2024.58542","type":"journal-article","created":{"date-parts":[[2025,2,7]],"date-time":"2025-02-07T16:32:35Z","timestamp":1738945955000},"page":"e2458542","source":"Crossref","is-referenced-by-count":3,"title":["Financial Incentives for COVID-19 Vaccination"],"prefix":"10.1001","volume":"8","author":[{"given":"John","family":"Ternovski","sequence":"first","affiliation":[{"name":"Office of Labor and Economic Analysis, Department of Economics and Geosciences, Air Force Academy, Colorado Springs, Colorado"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Sebastian","family":"Jilke","sequence":"additional","affiliation":[{"name":"McCourt School of Public Policy, Georgetown University, Washington, DC"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Florian","family":"Keppeler","sequence":"additional","affiliation":[{"name":"Department of Political Science, Aarhus University, Aarhus, Denmark"},{"name":"Department of Political and Social Sciences, Zeppelin University, Friedrichshafen, Germany"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Dominik","family":"Vogel","sequence":"additional","affiliation":[{"name":"Department of Administrative Sciences, Harz University of Applied Sciences, Halberstadt, Germany"}],"role":[{"role":"author","vocabulary":"crossref"}]}],"member":"10","published-online":{"date-parts":[[2025,2,7]]},"reference":[{"issue":"1","key":"zoi241635r1","doi-asserted-by":"publisher","first-page":"21","DOI":"10.1001\/jama.2019.18061","article-title":"Moving toward evidence-based policy: the value of randomization for program and policy implementation.","volume":"323","author":"Venkataramani","year":"2020","journal-title":"JAMA"},{"issue":"1","key":"zoi241635r2","doi-asserted-by":"publisher","first-page":"35","DOI":"10.1186\/s12961-017-0192-x","article-title":"Evidence-based policymaking is not like evidence-based medicine, so how far should you go to bridge the divide between evidence and policy?","volume":"15","author":"Cairney","year":"2017","journal-title":"Health Res Policy Syst"},{"issue":"7999","key":"zoi241635r3","doi-asserted-by":"publisher","first-page":"491","DOI":"10.1038\/s41586-023-06972-y","article-title":"Optimally generate policy-based evidence before scaling.","volume":"626","author":"List","year":"2024","journal-title":"Nature"},{"key":"zoi241635r4","doi-asserted-by":"publisher","DOI":"10.1016\/j.eclinm.2022.101632","article-title":"Crowdsourcing interventions to promote uptake of COVID-19 booster vaccines.","volume":"53","author":"B\u00f6hm","year":"2022","journal-title":"EClinicalMedicine"},{"issue":"2","key":"zoi241635r5","doi-asserted-by":"publisher","first-page":"1037","DOI":"10.1287\/mnsc.2022.4405","article-title":"Incentives and defaults can increase COVID-19 vaccine intentions and test demand.","volume":"69","author":"Serra-Garcia","year":"2023","journal-title":"Manage Sci"},{"key":"zoi241635r6","doi-asserted-by":"publisher","first-page":"75","DOI":"10.1016\/j.ypmed.2015.03.001","article-title":"Personal financial incentives for changing habitual health-related behaviors: a systematic review and meta-analysis.","volume":"75","author":"Mantzari","year":"2015","journal-title":"Prev Med"},{"issue":"3","key":"zoi241635r7","doi-asserted-by":"publisher","DOI":"10.1371\/journal.pone.0090347","article-title":"The effectiveness of financial incentives for health behaviour change: systematic review and meta-analysis.","volume":"9","author":"Giles","year":"2014","journal-title":"PLoS One"},{"issue":"1","key":"zoi241635r8","doi-asserted-by":"publisher","first-page":"1059","DOI":"10.1186\/s12889-019-7407-8","article-title":"Changing health behaviors using financial incentives: a review from behavioral economics.","volume":"19","author":"Vlaev","year":"2019","journal-title":"BMC Public Health"},{"issue":"15","key":"zoi241635r9","doi-asserted-by":"publisher","first-page":"1451","DOI":"10.1001\/jama.2019.2560","article-title":"The uncertain effect of financial incentives to improve health behaviors.","volume":"321","author":"Thirumurthy","year":"2019","journal-title":"JAMA"},{"issue":"8","key":"zoi241635r10","doi-asserted-by":"publisher","DOI":"10.1001\/jamanetworkopen.2021.22581","article-title":"Addition of financial incentives to mailed outreach for promoting colorectal cancer screening: a systematic review and meta-analysis.","volume":"4","author":"Facciorusso","year":"2021","journal-title":"JAMA Netw Open"},{"issue":"6569","key":"zoi241635r11","doi-asserted-by":"publisher","first-page":"879","DOI":"10.1126\/science.abm0475","article-title":"Monetary incentives increase COVID-19 vaccinations.","volume":"374","author":"Campos-Mercade","year":"2021","journal-title":"Science"},{"issue":"7944","key":"zoi241635r12","doi-asserted-by":"publisher","first-page":"526","DOI":"10.1038\/s41586-022-05512-4","article-title":"Financial incentives for vaccination do not have negative unintended consequences.","volume":"613","author":"Schneider","year":"2023","journal-title":"Nature"},{"issue":"6","key":"zoi241635r13","doi-asserted-by":"publisher","first-page":"411","DOI":"10.1037\/hea0001288","article-title":"The effectiveness of nonfinancial interventions and monetary incentives on COVID-19 vaccination: a meta-analysis.","volume":"42","author":"Huang","year":"2023","journal-title":"Health Psychol"},{"key":"zoi241635r14","doi-asserted-by":"publisher","DOI":"10.1016\/j.ypmed.2023.107538","article-title":"The effectiveness of financial incentives for COVID-19 vaccination: a systematic review.","volume":"172","author":"Khazanov","year":"2023","journal-title":"Prev Med"},{"key":"zoi241635r15","doi-asserted-by":"publisher","DOI":"10.1016\/j.jhealeco.2020.102386","article-title":"It runs in the family\u2014influenza vaccination and spillover effects.","volume":"74","author":"Bouckaert","year":"2020","journal-title":"J Health Econ"},{"key":"zoi241635r16","doi-asserted-by":"publisher","first-page":"c2220","DOI":"10.1136\/bmj.c2220","article-title":"Improving immunisation coverage in rural India: clustered randomised controlled evaluation of immunisation campaigns with and without incentives.","volume":"340","author":"Banerjee","year":"2010","journal-title":"BMJ"},{"issue":"1","key":"zoi241635r17","doi-asserted-by":"publisher","first-page":"95","DOI":"10.1257\/pol.20170067","article-title":"Direct and spillover effects of middle school vaccination requirements.","volume":"11","author":"Carpenter","year":"2019","journal-title":"Am Econ J Econ Policy"},{"key":"zoi241635r18","first-page":"745","article-title":"The cost of price incentives: an empirical analysis of motivation crowding-out.","volume":"87(4)","author":"Frey","year":"1997","journal-title":"Am Econ Rev"},{"issue":"4","key":"zoi241635r19","doi-asserted-by":"publisher","first-page":"191","DOI":"10.1257\/jep.25.4.191","article-title":"When and why incentives (don\u2019t) work to modify behavior.","volume":"25","author":"Gneezy","year":"2011","journal-title":"J Econ Perspect"},{"issue":"3","key":"zoi241635r20","doi-asserted-by":"publisher","first-page":"791","DOI":"10.1162\/003355300554917","article-title":"Pay enough or don\u2019t pay at all.","volume":"115","author":"Gneezy","year":"2000","journal-title":"Q J Econ"},{"key":"zoi241635r21","doi-asserted-by":"publisher","first-page":"c332","DOI":"10.1136\/bmj.c332","article-title":"CONSORT 2010 statement: updated guidelines for reporting parallel group randomised trials.","volume":"340","author":"Schulz","year":"2010","journal-title":"BMJ"},{"issue":"1","key":"zoi241635r23","doi-asserted-by":"publisher","first-page":"332","DOI":"10.1093\/ije\/dyx201","article-title":"Spillover effects in epidemiology: parameters, study designs and methodological considerations.","volume":"47","author":"Benjamin-Chung","year":"2018","journal-title":"Int J Epidemiol"},{"issue":"1","key":"zoi241635r24","doi-asserted-by":"publisher","first-page":"65","DOI":"10.1111\/j.1745-9125.2012.00290.x","article-title":"Foot patrol in violent crime hot spots: the longitudinal impact of deterrence and posttreatment effects of displacement.","volume":"51","author":"Sorg","year":"2013","journal-title":"Criminology"},{"issue":"1","key":"zoi241635r25","doi-asserted-by":"publisher","first-page":"1901","DOI":"10.1038\/s41598-024-51590-x","article-title":"Policy makers believe money motivates more than it does.","volume":"14","author":"Jilke","year":"2024","journal-title":"Sci Rep"},{"issue":"8019","key":"zoi241635r27","doi-asserted-by":"publisher","first-page":"179","DOI":"10.1038\/s41586-024-07591-x","article-title":"Megastudy shows that reminders boost vaccination but adding free rides does not.","volume":"631","author":"Milkman","year":"2024","journal-title":"Nature"},{"issue":"31","key":"zoi241635r28","doi-asserted-by":"publisher","DOI":"10.1073\/pnas.2302725120","article-title":"Reminders, but not monetary incentives, increase COVID-19 booster uptake.","volume":"120","author":"Chang","year":"2023","journal-title":"Proc Natl Acad Sci U S A"},{"issue":"5","key":"zoi241635r29","doi-asserted-by":"publisher","DOI":"10.1371\/journal.pone.0248372","article-title":"Attitudes on voluntary and mandatory vaccination against COVID-19: evidence from Germany.","volume":"16","author":"Graeber","year":"2021","journal-title":"PLoS One"},{"issue":"4","key":"zoi241635r30","doi-asserted-by":"publisher","DOI":"10.1371\/journal.pone.0266659","article-title":"The COVID-19 vaccine: trust, doubt, and hope for a future beyond the pandemic in Germany.","volume":"17","author":"Fiske","year":"2022","journal-title":"PLoS One"},{"issue":"16","key":"zoi241635r31","first-page":"1","article-title":"Coronavirus conspiracy beliefs in the German-speaking general population: endorsement rates and links to reasoning biases and paranoia.","volume":"52","author":"Kuhn","year":"2021","journal-title":"Psychol Med"},{"issue":"36","key":"zoi241635r32","doi-asserted-by":"publisher","DOI":"10.1073\/pnas.2109543118","article-title":"Incentives can spur COVID-19 vaccination uptake.","volume":"118","author":"Kl\u00fcver","year":"2021","journal-title":"Proc Natl Acad Sci U S A"},{"issue":"14","key":"zoi241635r33","doi-asserted-by":"publisher","first-page":"1343","DOI":"10.1001\/jama.2020.3413","article-title":"Priorities for the US health community responding to COVID-19.","volume":"323","author":"Adalja","year":"2020","journal-title":"JAMA"},{"issue":"1","key":"zoi241635r34","doi-asserted-by":"publisher","first-page":"1882","DOI":"10.1186\/s12889-021-11925-z","article-title":"Public health preparedness and response synergies between institutional authorities and the community: a qualitative case study of emerging tick-borne diseases in Spain and the Netherlands.","volume":"21","author":"de Vries","year":"2021","journal-title":"BMC Public Health"},{"key":"zoi241635r22","unstructured":"German Federal Statistical Office. Type of communication with public authorities. Focus on the digitalization of the Federal Statistical Office\u2019s life situation survey. 2021. Accessed August 12, 2024. https:\/\/www.amtlich-einfach.de\/DE\/Ergebnisse\/Buerger2021\/Digitalisierung\/Digitalisierung_node.html"},{"key":"zoi241635r26","unstructured":"Gerber? AS, Green? DP. Field experiments: design, analysis, and interpretation. 2012. Accessed August 12, 2024. https:\/\/external.dandelon.com\/download\/attachments\/dandelon\/ids\/CH001CB8AFC4CB182BA9AC1257BC70035C7C0.pdf"}],"container-title":["JAMA Network Open"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/jamanetwork.com\/journals\/jamanetworkopen\/articlepdf\/2830030\/ternovski_2025_oi_241635_1738258971.19522.pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2025,2,7]],"date-time":"2025-02-07T16:32:41Z","timestamp":1738945961000},"score":1,"resource":{"primary":{"URL":"https:\/\/jamanetwork.com\/journals\/jamanetworkopen\/fullarticle\/2830030"}},"subtitle":["A Cluster Randomized Clinical Trial"],"short-title":[],"issued":{"date-parts":[[2025,2,7]]},"references-count":34,"journal-issue":{"issue":"2","published-print":{"date-parts":[[2025,2,3]]}},"URL":"https:\/\/doi.org\/10.1001\/jamanetworkopen.2024.58542","relation":{},"ISSN":["2574-3805"],"issn-type":[{"value":"2574-3805","type":"electronic"}],"subject":[],"published":{"date-parts":[[2025,2,7]]}}}