COST-EFFECTIVENESS OF PNEUMOCOCCAL CONJUGATE VACCINATION IN THE IMMUNOCOMPROMISED

Purpose: Pneumococcal disease is a leading cause of mortality and morbidity, particularly in immunocompromised persons, but the currently recommended pneumococcal polysaccharide vaccine (PPSV) has limited effectiveness in this group. Some evidence suggests that the pneumococcal conjugate vaccine (PCV), newly approved for adults and more costly than PPSV, is effective in the immunocompromised, but its cost-effectiveness is unknown.

Method: We used a Markov model to estimate the cost effectiveness of 4 vaccination strategies in immunocompromised persons: no vaccine, a single PPSV, two PPSV doses 5 years apart (the CDC recommendation), and a single PCV. We considered, over a 15-year time horizon, immunocompromised persons aged 18-64 years (average life expectancy 11.7 years). Pneumococcal disease rates were obtained from US databases, as were childhood vaccination indirect effect projections. PCV effectiveness was estimated by a Delphi expert panel; PPSV protection was modeled relative to PCV effectiveness. In the model, both vaccines prevented invasive pneumococcal disease (IPD), but only PCV prevented nonbacteremic pneumococcal pneumonia (NPP), consistent with published data. Illness costs were obtained from the Nationwide Inpatient Sample and utilities taken from the literature. We used 2006 US costs, took a societal perspective, discounted costs and effectiveness 3%/yr, and used a $100,000/QALY cost-effectiveness criterion.

Result: Compared to no vaccination, PCV cost $70,900/QALY gained if PPSV relative effectiveness compared to PCV was <53%; if PPSV relative effectiveness is >72%, single-dose PPSV was favored. Extended dominance eliminated two-dose PPSV in all analyses. In HIV patients, who have longer life expectancy (22.5 years), PCV was favored unless PPSV effectiveness is >93% of PCV's. A major driver of results was PCV effectiveness against NPP, which is unclear, particularly in the immunocompromised; PCV is not favored in the base case if its NPP effectiveness relative to its IPD effectiveness was ≤49% (expert estimate 70%, dashed line in figure). The Figure depicts a 2-way sensitivity analysis, varying PPSV relative effectiveness (x-axis) and PCV effectiveness against NPP (y-axis). Probabilistic sensitivity analyses supported these results.  

Conclusion: PCV in immunocompromised patients appears to be economically reasonable; however, the decision is sensitive to assumptions regarding overall PPSV effectiveness and PCV effectiveness against NPP. PCV is more strongly favored in HIV patients, due to their longer life expectancy. A two-dose PPSV strategy, as recommended by the CDC, is dominated.