Modelling the Impact on Greenhouse Gas Emissions From Using a High Dose Compared With a Standard Dose Influenza Vaccine in Adults Aged 65 Years and Older in France

Background: The healthcare system accounts for 8% of total carbon dioxide emissions in France. Vaccines are proven to mitigate the burden of infectious diseases and reduce healthcare utilization. This study aimed to assess the environmental impact on the French healthcare system of using a high-dose (HD) influenza vaccine instead of a standard-dose (SD), by modelling greenhouse gas (GHG) emissions in the care pathway for 65+ in France. Methods: A model was developed applying GHG emission factors to avoided health outcomes through HD instead of SD vaccination, considering the increased GHG emissions from vaccine production. Outcomes from a health economic model populated with French epidemiological data were used, estimating avoided influenza-related primary care visits, emergency visits, and hospitalizations for the HD vaccine based on superior vaccine efficacy (24.2% higher for the HD vaccine than the SD vaccine). A vaccination coverage rate of 60% was used as a baseline and 75% as an exploratory scenario in line with World Health Organization (WHO) targets. Two hospitalization approaches were considered: 1/ based on influenza hospitalizations and 2/ including cardio-respiratory complications triggered by influenza. Emissions factors from France were used for hospitalizations, while UK data were adjusted and used for primary care visits and emergency visits. Results: During an average season, if 60% of older adults were vaccinated with HD instead of SD, 5.0 kilotons of carbon dioxide equivalent (kt CO ₂ eq) could be avoided per year considering hospitalizations for influenza, and 32.2 kt CO ₂ eq when cardio-respiratory complications are included. At the 75% WHO target, from 6.2 to 40.2 kt CO ₂ eq would be avoided. Avoided hospitalizations represented up to 95% of the avoided carbon emissions. The higher GHG emissions from HD vaccine production were compensated by avoided GHG emissions from prevented health outcomes in the approach for influenza hospitalizations, and the intervention exceeded the carbon-efficiency threshold when including cardio-respiratory complications. Conclusions: Despite a higher carbon footprint from vaccine production, the use of an HD vaccine rather than an SD vaccine reduced GHG emissions throughout the care pathway and is therefore at least carbon efficient while delivering tangible public health benefits for 65+.