Background: Older adults aged 65 years and above have declines in their health status, being exposed to more diseases including infections with more severe cases at older age. Aim: Current disease management strategy against respiratory infection is investigated to identify and measure the economic paradox of more infection, more cost, less health gain in the more aged people. Method: Modelling considers the heterogenous condition of the ageing population related to demography Fage, sex), health condition, place of living, exposure to respiratory infection, care given, cost, and quality health lost. Outcome is expressed as a cost, a Quality Adjusted Life Year (QALY)-loss, a Cost/ QALY-loss (C/Q), and an economic paradox index being the ratio of C/Q for a specific subgroup over a reference group. Sensitivity analysis assesses the paradox level through changes in specific mortality, infection rate, disease duration, and cost. Results: A 1-year population model, called the AMAI-model, for the year 2023 of the Flemish County is built with all the characteristics known of the aging population (65y+, n = 1 430 423). The model illustrates the paradox of technical inefficiency that is essentially driven by 2 variables: specific mortality rate at younger age causing critical survival loss and the high cost of hospitalisation in the very aged population (Cost/QALY-loss: 11,327€ and 106,498€ respectively for Young and Old age-groups). The paradox index goes up to 9.4 for the Old age-group compared to the Young aged group. Changing survival loss to no specific deaths leads to the disappearing of the paradox, while increasing the infection rate (+5%) and hospital cost (+20%) marginally accentuate the paradox. Conclusion: An economic paradox of respiratory infection exposure is likely to be present in ageing adults in the Flanders. It will be accentuated over time without specific new intervention as the 65y+ population is naturally growing in ageing.