Mitigating the impact of influenza on health systems: pandemic hospitalizations and seasonal vaccination behavior

Abstract

Influenza is one of the most widespread respiratory illnesses worldwide with annual seasonal and occasional pandemic outbreaks that excise heavy health and economic tolls on unprepared health systems. Therefore, countries invest considerable resources into combatting both seasonal and pandemic influenza, albeit in dissimilar manners due to their differing natures. Due to the unpredictability of pandemics, health policymakers focus on hospital capacity and resource allocation planning. They need accurate estimates of how hospitalizations, their severity, and costs dynamically change throughout pandemic and post-pandemic waves of infection. Compliance with preventive measures, including vaccination, is key for seasonal influenza. Better understanding of behavioral drivers of influenza vaccination and potential interventions that could increase uptake is crucial. This thesis thus addresses policymakers’ needs to mitigate seasonal influenza by examining the impact of social norms messaging, a behavioral intervention, on vaccination intention (Chapter 2). I find evidence of both bandwagoning and free-riding effects, depending on the level of social norms intensity. I further investigate behavioral drivers of child vaccination uptake given the dual risk-taking parents undergo when making vaccination decisions for themselves and their children (Chapter 3). Parent vaccination is associated with increased child vaccination only for children aged 10-years-old or over. To address policymakers’ needs to mitigate pandemic influenza, I estimate hospital admissions and associated costs due to the 2009 H1N1 pandemic and the 2010/11 post-pandemic flu season in England (Chapter 4). I find 22,123 H1N1 hospitalizations across England, costing an extra £45.4 million GBP. Furthermore, I estimate hospitalization severity, mortality, and time lags between infection and hospitalization (Chapter 5). Hospitalization rates are 34% higher and severity is 20-90% greater during the post-pandemic period compared to the pandemic. The results from this thesis can help inform mitigation strategies to prevent and combat seasonal and pandemic influenza and help policymakers design future healthcare interventions.