What are the main factors affecting the demonstration of cost-effectiveness of respiratory sincitial virus vacunes for adults above 60 years of age

Demonstrating the cost-effectiveness of respiratory syncytial virus (RSV) vaccines for adults aged 60 years and above depends on a convergence of epidemiological, clinical, economic, and programmatic factors. A robust analysis must specifically consider:1. Accurate Estimation of Disease BurdenA central input for any cost-effectiveness model is the true incidence and severity of RSV in the target population. Older adults experience significant RSV disease burden: pooled analyses reveal that RSV accounts for around 4.7–7.8% of symptomatic respiratory infections in adults ≥60, with case fatality rates reaching 8.2% in this age group[1]. Hospitalization rates are substantial, averaging 157 per 100,000 person-years in industrialized countries, with hospital mortality rates of 6–9%[2][3]. Critically, RSV leads to hospital stays that are both frequent and associated with high resource use, comparable to or exceeding influenza[2][4]. However, disease burden estimates are likely underreported due to diagnostic underuse in adults and variability in surveillance, which can lead to underestimation of vaccine benefit and thus reduced apparent cost-effectiveness[1][3].2. Clinical Effectiveness and Duration of ProtectionEfficacy evidence from recent phase 3 trials demonstrates that approved RSV vaccines show moderate to high protective effectiveness against lower respiratory tract illness and hospitalization in the target age group, with rates exceeding 60% for acute respiratory illness and up to 85% for more severe disease manifestations[5][6][7]. While the initial efficacy is promising, the duration of vaccine-induced protection is a critical modeling assumption. Some phase 1 data suggest immune responses can persist for at least two years post-immunization, potentially reducing the need for frequent revaccination[8]. However, real-world effectiveness over multiple RSV seasons remains an open question, especially given age-related immune decline[3][7].3. Cost Inputs: Direct Medical and Programmatic CostsHospitalization represents the major cost driver in RSV management among older adults. In the US alone, the annual direct cost burden attributable to RSV hospitalizations in adults ≥60 is estimated at $1.5–$4.0 billion[9]. Per-hospitalization costs for RSV are at least as high as for influenza ($16,034 \text{for} \text{RSV} vs$15,163 for influenza)[4]. Cost-effectiveness is highly sensitive to the unit cost per vaccine dose and the costs of implementation, including administration, outreach, and monitoring[9]. Moreover, country- and region-specific cost data are often lacking, presenting challenges to generalizability of economic assessments[9].4. Target Population, Risk Stratification, and UptakeCost-effectiveness improves when vaccination targets high-risk subgroups—such as those ≥75 years or with comorbidities—who exhibit the highest rates of severe RSV and resultant healthcare use[1][10][3]. Updated recommendations reflect this risk stratification: universal recommendation for adults ≥75 and continued stratification for those 60–74 at increased risk[10]. Vaccine uptake in real-world settings, influenced by healthcare delivery channels and patient acceptance, exposes further uncertainty—low uptake will erode population-level benefits even if per-person cost-effectiveness is favorable[10].5. Modeling Choices and Key AssumptionsEconomic evaluations of RSV vaccines for older adults rely on several critical assumptions:

• Incidence and severity of RSV used as input values (often underestimated due to underdiagnosis)
• Vaccine effectiveness over time, including waning immunity and possible need for repeat dosing (annual, biennial, or otherwise)[5][8][7]
• Discount rate for future costs and health outcomes (commonly 3–5%)
• Quality-adjusted life year (QALY) gains and how quality-of-life decrements due to RSV are valued—especially as comorbidities and baseline frailty in older adults complicate attribution[9][1].
• Exclusion or limited consideration of indirect costs, such as lost productivity and caregiver burden, which are typically less pronounced for this age demographic[9].

6. Real-world Effectiveness & Safety ConsiderationsWhile clinical trials indicate safety and robust efficacy, rare or very late adverse events—as well as actual vaccine effectiveness in diverse real-world populations—need ongoing assessment[6][10][3]. This dynamic will impact both public acceptability and the net benefit calculation in cost-effectiveness frameworks.7. Comparative Opportunity Cost and Budget ImpactCompeting health priorities and limited health budgets mean RSV vaccination must demonstrate not only favorable cost-effectiveness ratios compared to established thresholds, but also relative to other vaccination and preventive health programs targeting similar populations (e.g., influenza, pneumococcal vaccination)[10][9].8. Implementation FeasibilityIntegrating RSV vaccination into existing immunization programs can reduce incremental delivery costs and improve reach, but logistical complexities and overlapping campaigns must be managed[10][9].

In summary:The demonstration of cost-effectiveness for RSV vaccination in adults ≥60 is fundamentally linked to: accurate recognition of the disease burden (including overcoming underdiagnosis), validated estimates of vaccine efficacy (and duration of protection), high direct medical and societal costs (especially for severe outcomes such as hospitalization), rational prioritization of high-risk populations, realistic assumptions in health economic modeling, ongoing real-world safety/effectiveness surveillance, and streamlined implementation. Addressing data gaps—especially regarding true incidence, outcomes stratified by comorbidity status, and cost variance across healthcare systems—remains essential for maximizing the policy value and public health impact of RSV vaccination in older adults[5][1][10][9][3][7].