Wang, B.Andraweera, P.Danchin, M.Blyth, C.C.Vlaev, I.Ong, J.J.Dodd, J.Couper, J.Sullivan, T.R.Cuthbert, A.R.Rak, A.Herewane, K.Paparo, L.Karnon, J.Spurrier, N.Cusack, M.Mordaunt, D.Simatos, D.Dekker, G.Carlson, S.et al.2025-10-152025-10-152025Journal of Public Health, 2025; fdaf097-1-fdaf097-121741-38421741-3850https://hdl.handle.net/2440/147796OnlinePubl. Available online 6 August 2025Background: Non-coercive ‘nudge’ interventions have shown the potential to promote health behaviours. This study aimed to evaluate the impact of nudge interventions on COVID-19/influenza vaccine uptake among children with medically at-risk conditions. Methods: Randomized controlled trials (RCTs) were conducted, and participants were randomized (1:1) to standard care or intervention. The multicomponent nudge interventions included three text messages with video links, developed using the MINDSPACE framework. Results In the COVID-19 RCT, 554 were randomized to intervention and 552 to standard care, with 15.3% opting out of text messages. Over 3 months, eight children in the intervention group (1.4%) and nine in the standard care group (1.6%) received at least one dose of COVID-19 vaccine (odds ratio (OR): 0.89; 95% confidence interval (CI): 0.34–2.35). In the influenza RCT, 564 were randomized to intervention and 567 to standard care. There was no difference in the percentage vaccinated against influenza between the intervention (25.7%) and standard care (23.8%) groups (OR: 1.11; 95% CI: 0.85–1.45). Conclusions: The nudge interventions were ineffective at increasing COVID-19/influenza vaccine uptake. The study included mostly unvaccinated children, and low vaccination rates during the study likely impacted the evaluation results. Nudges may need to evolve with changes to public trust in technology and communications.en© The Author(s) 2025. Published by Oxford University Press on behalf of the Faculty of Public Health. All rights reserved. For commercial re-use, please contact reprints@oup.com for reprints and translation rights for reprints. All other permissions can be obtained through our RightsLink service via the Permissions link on the article page on our site—for further information please contact journals.permissions@oup.com.children; COVID-19; infectious diseaseJournal article10.1093/pubmed/fdaf097747861Andraweera, P. [0000-0003-2434-8370]Couper, J. [0000-0003-4448-8629]Karnon, J. [0000-0003-3220-2099]