Influenza vaccination in children with special risk medical conditions

Abstract

A considerable number of Australian children are at increased risk of disease or complications from influenza due to a medical condition. Focusing on the health of these children is a public health priority. Vaccination against influenza has been recommended in Australia for people with special risk medical conditions (SRMC) since 1991 (funded 2010). Despite this, vaccination coverage has not been routinely or uniformly measured. The primary aim of this thesis was to identify barriers to coverage in children identified at increased risk of influenza and translate this into interventions that could address low coverage. This PhD thesis comprises five peer-reviewed published papers and one manuscript that present results from a systematic review and three observational studies. The systematic review assessed the current evidence of disease severity, complications and resource use experienced by children with SRMC who were hospitalised with influenza infection compared to healthy children. The first observational study was conducted with parents of children with a confirmed SRMC and examined confirmed influenza vaccination and reporting to Australian Immunisation Register (AIR). The second observational study used data from the 2016 South Australian Health Monitor survey to examine parental awareness of influenza vaccine recommendations. The third utilised a cross-sectional survey and qualitative interviews with the general practitioners (GP) and paediatric specialists, who were identified by parents as the children’s (from observational study 1) treating doctors. Additionally, an intervention to address barriers identified in this thesis was designed. Compared to healthy peers, children with SRMC hospitalised with influenza infection had higher odds of ICU admission [pooled odds ratio (OR) 1.66 (95% confidence interval (CI): 1.25–2.21)], mechanical ventilation [pooled OR 1.53 (95% CI: 0.93–2.52)], death [pooled OR 1.34 (95% CI: 0.74–2.41)] suspected bacterial pneumonia (crude OR 1.7; 95% CI: 1.1–2.6) and experienced prolonged hospital length of stay [adjusted rate ratio 1.75 (95% CI: 1.44–2.11)]. In children with SRMC (n=410) confirmed influenza vaccine receipt at least once in the last two years was 50%. Characteristics associated with uptake included: receiving a specialist (adjusted OR [aOR] 15.80, CI 6.69–37.29) or GP recommendation (aOR 6.76, CI 2.99–15.29) or annual parental receipt (aOR 11.12, CI 5.36–23.06). Sensitivity of the AIR to reflect a child’s influenza immunisation status was low (32.6%) and 78% of parent reported vaccinations were able to be substantiated by a provider with good (κ = 0.677) to very good agreement (κ = 0.814) for 2014 and 2015 respectively. Overall, 33% of parents in the community were aware that all children (<5 years) were recommended influenza vaccine annually, with this knowledge associated with an awareness of the recommendation for children with a SRMC (aOR 9.72, CI 4.14-22.82), living in a metropolitan area (aOR 2.67, CI 1.15-6.22) and being born in Australia (aOR 3.11, CI 1.12-8.65). Overall 51.9% of parents were aware of the recommendation that children with SRMCs should receive the vaccine annually, with this awareness associated with knowledge of the influenza recommendation for children <5 years (aOR 10.22, CI 4.39-23.77) or not being born in Australia [UK/ Ireland (aOR 7.63, CI 1.86- 31.31). The most influential cue to future receipt was a GP recommendation. Only 38.4% of medical practitioners reported they ‘always’ recommended influenza vaccine and less (19.5%) were very confident in understanding all SRMCs.