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Review
. 2022 May;20(3):395-404.
doi: 10.1007/s40258-021-00711-y. Epub 2022 Jan 10.

Herd Immunity Effects in Cost-Effectiveness Analyses among Low- and Middle-Income Countries

Siyu Ma  1 , Tara A Lavelle  2   3 , Daniel A Ollendorf  2   3 , Pei-Jung Lin  2   3
Affiliations
Review

Herd Immunity Effects in Cost-Effectiveness Analyses among Low- and Middle-Income Countries

Siyu Ma et al. Appl Health Econ Health Policy. 2022 May.

Abstract

Background: Herd immunity (HI) is a key benefit of vaccination programs, but the effects are not routinely included in cost-effectiveness analyses (CEAs).

Objective: This study investigated how the inclusion of HI in CEAs may influence the reported value of immunizations in low- and middle-income countries (LMICs) and illustrated the implications for COVID-19 immunization.

Methods: We reviewed immunization CEAs published from 2000 to 2018 focusing on LMICs using data from the Tufts Medical Center CEA Registries. We investigated the proportion of studies that included HI, the methods used, and the incremental cost-effectiveness ratios (ICERs) reported. When possible, we evaluated how ICERs would change with and without HI.

Results: Among the 243 immunization CEAs meeting inclusion criteria, 44 studies (18%) included HI. Of those studies, 11 (25%) used dynamic transmission models, whereas the remainder used static models. Sixteen studies allowed for ICER calculations with and without HI (n = 48 ratios). The inclusion of HI always resulted in more favorable ratios. In 20 cases (42%), adding HI decreased the ICERs enough to cross at least one or more common cost-effectiveness benchmarks for LMICs. Among pneumococcal vaccination studies, including HI in the analyses decreased seven of 24 ICERs enough to cross at least one cost-effectiveness benchmark.

Conclusion: The full value of immunization may be underestimated without considering a scenario in which HI is achieved. Given the evidence in pneumococcal CEAs, COVID-19 vaccine value assessments should aim to show ICERs with and without HI to inform decision-making in LMICs.

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Conflict of interest statement

The authors report grants from the Gates Foundation during the conduct of this study. The authors are affiliated with the CEA Registry, which receives unrestricted sponsorships from a number of government, private foundation, and pharmaceutical industry sponsors (list is available at https://cevr.tuftsmedicalcenter.org/sponsorship). DAO and SM report grants from GlaxoSmithKline, outside of the submitted work. DAO reports personal fees from the Center for Global Development, EMD Serono, Amgen, Analysis Group, Aspen Institute/University of Southern California, GalbraithWight, personal fees from Cytokinetics, Executive Insight, Sunovion, University of Colorado, AstraZeneca, Neurocrine, Alkermes, outside of the submitted work. TAL reports personal fees from Merck, outside of the submitted work. PJL reports no additional competing interests.

Figures

Fig. 1
Fig. 1
Literature review flow diagram. HIC high income country
See this image and copyright information in PMC

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