A randomised controlled trial to increase influenza vaccine uptake in children

Abstract

Background and Aims: Influenza is a leading infectious cause of childhood hospitalisation in Hong Kong. Children aged from 6 months to 12 years are recommended to receive influenza vaccine to prevent disease and reduce the impact of its complications. Influenza vaccine is not included in the Hong Kong Government’s Childhood Immunisation Programme but eligible children can receive subsidized vaccine through the Childhood Influenza Vaccination Subsidy Scheme (CIVSS). This study examined whether a simple intervention package can increase influenza vaccine uptake in Hong Kong children. Methods: Families of children who were enrolled in a previous knowledge, attitudes and practices study were invited to participate in this trial when the children reached 6 months of age. Children who had already received influenza vaccine were excluded. After enrollment, subjects were randomly allocated to control and intervention groups using block randomisation. At recruitment (11 November 2014-13 June 2015), subjects in the control group received the publically available leaflets from the Centre for Health Protection about the CIVSS. Subjects in the intervention group additionally received the following: (i) a concise information sheet about influenza and its vaccine; (ii) semi-completed consent forms to utilise vaccination subsidy if required; (iii) reminders and (iv) contacts of specific practitioners and clinics participating in CIVSS. At around 1 year of age (3 August-19 October 2015), mothers in both groups were contacted by phone so as to obtain their children's influenza vaccination history. Intention-to-treat analysis was used with missing status of influenza vaccination taken as no vaccination. Chi-square test was performed to compare influenza vaccine uptake between control and intervention groups using statistical software R version 3.2.1. Results: 208 subjects (44% of 493 mother-infant pairs from PDKAP cohort) were recruited with 104 subjects in each arm. Copies of immunisation records were obtained in 189 subjects (93%). One control subject (1%) and 28 intervention subjects (27%) received influenza vaccine before 1 year of age (p-value <0.001). Conclusions: A simple intervention package of concise information, pre-filled consent forms, reminders and practitioner contact details increased influenza vaccine uptake in Hong Kong children before 1 year of age.