Burden of Influenza and Cost-Effectiveness Analysis of Introduction of an Influenza Vaccination Programme Among Older Adults in India.

BACKGROUND: In India, no publicly funded seasonal influenza immunization is ongoing, partly because cost-effectiveness is yet to be established. We estimate the cost-effectiveness and budgetary impact of introducing seasonal influenza vaccination among adults aged ≥ 60 years in India, a known high-risk group. METHODS: Estimates of disease burden including disability adjusted life years (DALYs) were generated from 3-year community cohorts and hospital-based study set up at four sites to estimate incidence of symptomatic acute respiratory infections (ARI), health care utilization, costs and outcomes and applied to India's 2021 estimated population. We used a decision analysis model from an abridged societal perspective for implementation of an inactivated trivalent influenza vaccination programme for older adults (aged ≥ 60 years) using either facility-based or outreach-based approaches. We estimated incremental cost-effectiveness ratio (ICER) per DALY averted and used India's per capita gross domestic product of US 2238 for 2021 as the cost-effectiveness threshold. We performed deterministic and probabilistic sensitivity analyses. We also estimated ICER for immunizing all those above 65 years or with comorbidities. Using financial cost of the vaccination programme and the direct medical cost of disease averted we estimated its budgetary impact. RESULTS: In 2021, older adults in India had 5. 3 (95% CI: 3. 6-7. 7) million influenza-ARIs resulting in 36, 149 (95% CI: 30, 076-43, 268) hospitalizations and 84, 613 (95% CI: 39, 895-155, 454) deaths. It amounted to a total of 974, 019 DALYs and US 66. 6 million. As compared with no vaccination, facility-based and outreach-based influenza vaccination had an ICER of US1979 and US1851, respectively, below the cost-effectiveness threshold. In all sensitivity and scenario analyses, ICER estimates were below the threshold and vaccinating those above 60 years with specified comorbidities using a passive approach was found to be most cost-effective with least budgetary impact. CONCLUSION: Annually vaccinating older adults against influenza was found to be cost-effective in the majority of scenarios considered in the study. Given the budgetary implication, it might be prudent to focus on those with co-morbidities.