Evaluating the impact of population-based and cohort-based models in cost-effectiveness analysis: a case study of pneumococcal conjugate vaccines in infants in Germany.

OBJECTIVE

The objective of this analysis is to evaluate the impact of model choice (closed single-cohort versus population-based) in cost-effectiveness analysis (CEA) using pneumococcal conjugate vaccines (PCVs) in infants in Germany as a case study.

METHODS

Two Markov models were developed: one with a closed single-cohort model and one with a population-based model. Except for the design of the modelled population/cohort, all other inputs and characteristics were kept identical between the models. Comparators included PCV20 under a 3 + 1 vaccination schedule versus PCV13 and PCV15 under a 2 + 1 vaccination schedule. Health and economic outcomes were compared between the two models.

RESULTS

The population-based model demonstrated that PCV20 was cost-saving and provided better health outcomes compared to both PCV13 and PCV15, indicating PCV20 as the dominant strategy with negative ICERs per QALY. In contrast, the closed single-cohort model showed PCV20 was associated with higher total costs compared to PCV13 and PCV15.

CONCLUSION

This analysis highlights the importance of accurately identifying the relevant population when conducting CEAs of vaccines. This is particularly crucial when a vaccine produces indirect effects in individuals who are not directly vaccinated, as this otherwise leads to an underestimation of cost-effectiveness.