Objectives: (1) To develop methods for conducting cluster randomised trials of text messaging interventions utilising routine electronic health records at low cost; (2) to assess the effectiveness of text messaging influenza vaccine reminders in increasing vaccine uptake in patients with chronic conditions. Design: Cluster randomised trial with general practices as clusters. Setting: English primary care. Participants: 156 general practices, who used text messaging software, who had not previously used text message influenza vaccination reminders. Eligible patients were aged 18-64 in 'at-risk' groups. Interventions: Practices were randomly allocated to either an intervention or standard care arm in the 2013 influenza season (September to December). Practices in the intervention arm were asked to send a text message influenza vaccination reminder to their at-risk patients under 65. Practices in the standard care arm were asked to continue their influenza campaign as planned. Blinding: Practices were not blinded. Analysis was performed blinded to practice allocation. Main outcome measures: Practice-level influenza vaccine uptake among at-risk patients aged 18-64 years. Results: 77 practices were randomised to the intervention group (76 analysed, n at-risk patients=51 121), 79 to the standard care group (79 analysed, n at-risk patients=51 136). The text message increased absolute vaccine uptake by 2.62% (95% CI -0.09% to 5.33%), p=0.058, though this could have been due to chance. Within intervention clusters, a median 21.0% (IQR 10.2% to 47.0%) of eligible patients were sent a text message. The number needed to treat was 7.0 (95% CI -0.29 to 14.3). Conclusions: Patient follow-up using routine electronic health records is a low cost method of conducting cluster randomised trials. Text messaging reminders are likely to result in modest improvements in influenza vaccine uptake, but levels of patients being texted need to markedly increase if text messaging reminders are to have much effect. Trial registration number: ISRCTN48840025.
Bibliographical noteFunding Information:
The authors would like to thank Dr Tim Collier for performing randomisation, the LSHTM Clinical Trials Unit, in particular Professor Diana Elbourne and Dr Elizabeth Allen for their contributions to study design and the final manuscript, Noclor, Public Health England, the Cabinet Office, the Primary Care Research Network, the Department of Health, the Clinical Practice Research Datalink, ResearchOne, and iPLATO for their guidance and support. This work was supported by the Wellcome Trust grant number 098504/Z/12/Z and Public Health England.