Protocol version 2.7, 11/02/2014 Page 1 of 16 Protocol: A cluster randomised trial of text messaging reminders for influenza vaccine in patients under 65 in clinical risk groups in English primary care 1 Administrative information 1.1 Title A cluster randomised trial of text messaging reminders for influenza vaccine in patients under 65 in clinical risk groups in English primary care. 1.2 Trial registration Registered on clinicaltrials.gov. 1.3 Protocol version Version 2.7, 11 th February 2014 1.4 Funding Wellcome Trust Senior Clinical Fellowship award. 1.5 Roles and responsibilities Authors contributing to this protocol:  Emily Herrett, LSHTM  Liam Smeeth, LSHTM  Tjeerd van Staa, LSHTM  Diana Elbourne, LSHTM  Elizabeth Allen, LSHTM  Joanna Sturgess, LSHTM  Caroline Free, LSHTM  Hugo Harper, Cabinet Office  Michael Hallsworth, HMRC  Anna Sallis, Department of Health  Tim Collier, LSHTM  Tim Chadborn, Public Heath England