The clinical and economic value of enhanced influenza vaccines for the elderly in Argentina

Background: Enhanced influenza vaccines are the best option for the elderly. In 2021, Argentina introduced the MF59-adjuvanted inactivated influenza vaccine (aIIV) for individuals aged 65 years. and above, in the national immunization program. High dose inactivated influenza vaccine (HD-IIV) is also currently registered. This study evaluates the clinical and economic outcomes of these noted enhanced influenza vaccines for the elderly in Argentina.

Methods: Using a static decision-tree model and adopting the payer's perspective during an average influenza season, the analysis incorporated influenza epidemiological data from pre-pandemic Argentinian seasons (2014-2019), strain distribution, vaccination uptake, influenza-related costs and Quality-Adjusted Life-Years (QALYs) gained. Results include two relative vaccine effectiveness (rVE) scenarios from two published meta-analyses, due to reported rVE variability, although without statistical significance expected between enhanced vaccines. Vaccination acquisition costs were obtained from aIIV manufacturer, while HD-IIV costs were estimated using local (Argentinian private sector) and international public sector data (Europe). This assessment considered one GDP per-capita (US$13,696) as a cost-effectiveness threshold and included multiple sensitivity analysis.

Results: With an expected lower vaccine cost and non-significant higher rVE for aIIV vs HD-IIV (3.2 %), aIIV generated 41.4 QALYs gained and US$8.7 M savings to the Argentinean public health system. In this scenario aIIV resulted as a dominant strategy over HD-IIV. On a second scenario, where HD-IIV has a non-significant higher rVE compared to aIIV (15.9 % and 13.9 % for HD-IIV and aIIV, respectively, both vs standard-dose IIV), HD-IIV would only result cost-effective compared to aIIV if its public price is up to 25 % the incremental cost in relation to the standard-dose IIV acquisition price.

Conclusions: In Argentina, the use of enhanced influenza vaccines in the elderly can increase vaccine effectiveness, reduce mortality and disease-related costs. Based on comparable effectiveness, the economic advantage of aIIV over HD-IIV confirms the current vaccination strategy employing aIIV in Argentina.