Impact of funding on influenza vaccine uptake in Australian children.

Objectives and importance of study: Young children are at higher risk for serious influenza outcomes but, historically, Australian children aged less than 5 years have had low seasonal influenza vaccine uptake. In 2018, most Australian jurisdictions implemented funded influenza vaccine programs targeted at improving vaccine uptake in this age group. Our aim was to determine how successful these programs were at improving self-reported seasonal influenza vaccine uptake at the community level by comparing vaccination rates in each Australian jurisdiction before and after the introduction of funded vaccines for children aged 6 months to less than 5 years, as well as other age groups. STUDY TYPE Volunteer observational cohort study. METHODS Flutracking is an email-based surveillance tool for influenza-like illness that collects information about symptoms and influenza vaccination. We used historical data from 2014 to 2017 to estimate baseline vaccination status before funding of childhood influenza vaccines was introduced. We compared self-reported vaccine uptake in children younger than 5 years, children aged 5-17 years and adults (18-64 years, and 65 years and older) in 2018 and 2019 by state or territory. Mixed effects logistic regressions were used to measure the association between vaccination and a number of predictors, including whether the child was eligible for free vaccines, and whether adults resided with children or not. RESULTS We found large increases in vaccine uptake for children younger than 5 years in 2018 in all jurisdictions except Western Australia (where vaccines were already funded) and the Northern Territory (where funded vaccines were not introduced until 2019) that coincided with vaccine policy changes. Self-reported vaccination rates for young children in 2018 increased 2.7-4.2-fold in jurisdictions that funded the vaccine (compared with the previous, unfunded period). Being eligible for the funded vaccine was associated with much higher odds (odds ratio [OR] 4.75; 95% confidence interval [CI] 4.57, 4.79) of a young child being vaccinated. Older children and adults younger than 65 years were also more likely to receive the vaccine following policy changes. CONCLUSION The seasonal influenza vaccine is an important protective measure for those at risk of serious outcomes, including young children. Flutracking data demonstrates that government-funded vaccines can lead to an almost five-fold increase in self-reported vaccine uptake of the targeted age group, as well as previously unreported flow-on effects to older children. This suggests that funded vaccines for young children may encourage caregivers to also vaccinate themselves and their older children.