CONSIDERATION OF INDIRECT EFFECTS IN NATIONAL VACCINE EVALUATIONS AND RECOMMENDATIONS: A SCOPING REVIEW
Author(s)
Min Huang, PhD1, Weiguang Xue, MSc2, Yanwen Xie, MSc3, Jack Eales, Msc2, Walter A. Orenstein, MD4, Zinan Yi, PhD1, Rachel J. Oidtman, PhD1, Elamin Elbasha, BSc, MA, PhD1, Michael Drummond, MCom, DPhil5;
1Merck & Co. Inc., Rahway, NJ, USA, 2Analysis Group Ltd., London, United Kingdom, 3Analysis Group, Inc., Los Angeles, CA, USA, 4School of Medicine, Emory University, Atlanta, GA, USA, 5Centre for Health Economics, University of York, York, United Kingdom
1Merck & Co. Inc., Rahway, NJ, USA, 2Analysis Group Ltd., London, United Kingdom, 3Analysis Group, Inc., Los Angeles, CA, USA, 4School of Medicine, Emory University, Atlanta, GA, USA, 5Centre for Health Economics, University of York, York, United Kingdom
OBJECTIVES: Guidance from the World Health Organization and other organizations recommends considering indirect effects, such as herd immunity, serotype replacement, and age shift, in vaccine value assessments. This scoping review examined whether and how indirect effects are considered in national vaccine evaluations and recommendations.
METHODS: Vaccine evaluation frameworks from seven national immunization technical advisory groups (NITAGs) were reviewed: US ACIP, UK JCVI, Canada NACI, Australia ATAGI, France CTV, Germany STIKO, and the Netherlands Health Council. Case studies of pneumococcal conjugate vaccine (PCV) and human papillomavirus (HPV) vaccine evaluations by the ACIP and JCVI were assessed. Supplementary searches in MEDLINE and Embase (July 2025) identified publications describing NITAG evaluation practices or perspectives related to indirect effects.
RESULTS: Two NITAGs (JCVI and CTV) did not publish formal evaluation frameworks. Although JCVI generally follows the methodological guidance from the National Institute for Health and Care Excellence for economic evaluation, it does not publish guidelines. Three NITAGs (ACIP, ATAGI, and STIKO) explicitly referenced indirect effects beyond herd immunity, including serotype replacement and age shift. NACI recommended considering positive and negative indirect effects, while the Netherlands Health Council treated herd effects primarily as vaccination goals rather than evaluation criteria. In case studies, ACIP documentation provided limited detail on indirect effects, which were typically addressed through economic evaluations. In contrast, JCVI meeting minutes documented extensive discussion of herd immunity, serotype replacement, and age shift across epidemiological, modeling, and decision-making contexts. Differences in publicly available source materials may explain this contrast. Among 19 studies identified in the supplementary searches, most mentioned indirect effects briefly, and none detailed how NITAGs quantified or weighted them in decision-making.
CONCLUSIONS: Although indirect effects are widely acknowledged, their evaluation in national vaccine decision-making remains inconsistent and methodologically underdeveloped. Clearer guidance on assessing indirect effects could improve cross-country comparability and support evidence generation.
METHODS: Vaccine evaluation frameworks from seven national immunization technical advisory groups (NITAGs) were reviewed: US ACIP, UK JCVI, Canada NACI, Australia ATAGI, France CTV, Germany STIKO, and the Netherlands Health Council. Case studies of pneumococcal conjugate vaccine (PCV) and human papillomavirus (HPV) vaccine evaluations by the ACIP and JCVI were assessed. Supplementary searches in MEDLINE and Embase (July 2025) identified publications describing NITAG evaluation practices or perspectives related to indirect effects.
RESULTS: Two NITAGs (JCVI and CTV) did not publish formal evaluation frameworks. Although JCVI generally follows the methodological guidance from the National Institute for Health and Care Excellence for economic evaluation, it does not publish guidelines. Three NITAGs (ACIP, ATAGI, and STIKO) explicitly referenced indirect effects beyond herd immunity, including serotype replacement and age shift. NACI recommended considering positive and negative indirect effects, while the Netherlands Health Council treated herd effects primarily as vaccination goals rather than evaluation criteria. In case studies, ACIP documentation provided limited detail on indirect effects, which were typically addressed through economic evaluations. In contrast, JCVI meeting minutes documented extensive discussion of herd immunity, serotype replacement, and age shift across epidemiological, modeling, and decision-making contexts. Differences in publicly available source materials may explain this contrast. Among 19 studies identified in the supplementary searches, most mentioned indirect effects briefly, and none detailed how NITAGs quantified or weighted them in decision-making.
CONCLUSIONS: Although indirect effects are widely acknowledged, their evaluation in national vaccine decision-making remains inconsistent and methodologically underdeveloped. Clearer guidance on assessing indirect effects could improve cross-country comparability and support evidence generation.
Conference/Value in Health Info
2026-05, ISPOR 2026, Philadelphia, PA, USA
Value in Health, Volume 29, Issue S6
Code
P15
Topic
Health Technology Assessment
Topic Subcategory
Decision & Deliberative Processes, Value Frameworks & Dossier Format
Disease
No Additional Disease & Conditions/Specialized Treatment Areas, STA: Vaccines