Indirect Effects in Health Economic Models of Vaccines: Should We Include Them, and How Do We Model Them?

This peer-reviewed current opinion article discusses whether and how indirect effects of vaccination should be incorporated into health economic models. Drawing on examples from rotavirus and pneumococcal vaccines, the article compares static models and dynamic transmission models, highlighting how methodological choices can influence estimates of vaccine impact and cost-effectiveness. 

Key findings and insights

• Indirect effects, including herd protection, serotype replacement, and age shifts, can substantially affect the estimated health and economic value of vaccination programs.
• Static models can incorporate indirect effects through simplified assumptions, but results are often highly sensitive to the magnitude, duration, and data sources used for these assumptions.
• Dynamic transmission models can more directly capture population-level transmission effects, but require greater technical expertise, more detailed data, and careful validation.
• The article’s examples show that different assumptions about indirect effects can lead to divergent cost-effectiveness conclusions, even for the same vaccine comparison.
• The authors call for better surveillance data, clearer methodological guidance, standardized reporting, and ongoing model validation after vaccine introduction.

Thumbnail image credit: Gavi