There are few estimates of the effectiveness of long-standing vaccination programs in developed countries. To fill this gap, we investigate the direct and indirect effectiveness of childhood vaccination programs on mortality at the population level in the Netherlands.
We focused on three communicable infectious diseases, diphtheria, pertussis, and poliomyelitis, for which we expect both direct and indirect effects. As a negative control, we used tetanus, a noncommunicable infectious disease for which only direct effects are anticipated. Mortality data from 1903 to 2012 were obtained from Statistics Netherlands. Vaccination coverage data were obtained from various official reports. For the birth cohorts 1903 through 1975, all-cause and cause-specific childhood mortality burden was estimated using restricted mean lifetime survival methods, and a model was used to describe the prevaccination decline in burden. By projecting model results into the vaccination era, we obtained the expected burden without vaccination. Program effectiveness was estimated as the difference between observed and expected mortality burden.
Each vaccination program showed a high overall effectiveness, increasing to nearly 100% within 10 birth cohorts. For diphtheria, 14.9% (95% uncertainty interval [UI] = 12.3%, 17.6%) of mortality burden averted by vaccination was due to indirect protection. For pertussis, this was 32.1% (95% UI = 31.3%, 32.8%). No indirect effects were observed for poliomyelitis or tetanus with −2.4% (UI = −16.7%, 7.1%) and 0.6% (UI = −17.9%, 10.7%), respectively.
Vaccination programs for diphtheria and pertussis showed substantial indirect effects, providing evidence for herd protection.
From the aCentre for Infectious Disease Control, National Institute for Public Health and the Environment, Bilthoven, the Netherlands; bUnit of PharmacoTherapy, -Epidemiology and -Economics, Groningen Research Institute of Pharmacy, University of Groningen, Groningen, the Netherlands; cInstitute of Science in Healthy Aging & healthcaRE (SHARE), University Medical Center Groningen (UMCG), Groningen, the Netherlands; and dDepartment of Medical Statistics and Bioinformatics, Leiden University Medical Center (LUMC), Leiden, the Netherlands.
Submitted March 22, 2017; accepted October 27, 2017.
Code and Data: The data are not yet available for replication because they will be made publically available through the Dutch National Institute for Public Health and the Environment at a later date. Code used in the analysis is available upon request.
M.v.W. obtained, extracted, and analyzed the data; searched the scientific literature; and wrote the first draft of the manuscript. M.v.W., S.A.M., H.E.d.M., M.J.P., and J.W. designed the study and revised the manuscript. M.J.P. and J.W. conceived the project.
This work was supported by the Dutch Ministry of Health, Welfare and Sport.
Disclosure: M.J.P. received grants and honoraria from various pharmaceutical companies, including GlaxoSmithKline, Pfizer, and Sanofi Pasteur MSD, who are potentially interested in the subject matter of this article. The other authors have no conflicts to report.
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Correspondence: Maarten van Wijhe, Center for Infectious Disease Control, National Institute for Public Health and the Environment, PO Box 1, 3720 BA Bilthoven, the Netherlands. E-mail: firstname.lastname@example.org.