OBJECTIVES: Influenza vaccine availability is crucial for managing seasonal influenza, especially with 7.2 million patients on NHS waiting lists for elective care. Increased influenza-related hospitalizations would worsen this crisis. Seasonal variations and manufacturing processes can cause vaccine shortages. Relying on single-supplier poses risks if they cannot meet demand. This study assesses the clinical and financial impact of influenza vaccine shortage on the NHS and workforce productivity.

METHODS: A static decision-tree model was used to quantify changes in disease burden from influenza vaccine shortages in England and Wales. At-risk population included 9.5 million individuals aged 18-64 and 11.1 million aged 65+. The model used UKHSA's 2021-22 season vaccine coverage rates of 53% for at-risk individuals aged 18-64 and 82% for those aged 65+, to calculate a full supply scenario.

Influenza hospitalizations were calculated using age-stratified rates from a Hospital Episodic Statistics study. Analysis included age-adjusted, influenza-related primary care and emergency department (ED) visits, hospitalizations, mortality data, and productivity loss, simulating the effects of reduced influenza vaccine supply over a season. 2022 NHS tariffs informed the associated costs.

RESULTS: From a baseline of 749,836 cases, every 20% reduction in vaccine supply results in an approximately 12% increase for each measured outcome. In absolute numbers, this is an increase of 93,772 influenza cases, 2,526 influenza-related ED visits, 1874 hospitalizations, 25,039 GP visits and 359,810 lost workdays. Increases in healthcare utilisation has financial consequences, e.g. Each 20% reduction in supply results in an additional £1,051,638 spent on GP visits.

CONCLUSIONS: The findings highlight the risks of a single-supplier model and the adverse impact of shortages on influenza incidence, healthcare utilisation, and workforce productivity. This analysis uses static model; indirect impact of increased disease transmission of supply shortages is not considered. A reliable supply through multi-supplier approach is critical for healthcare-system resilience during influenza seasons.