17.01.2012
Neue Ansätze der mathematischen Modellierung zeigen, dass beim Einsatz einer Malariaimpfung gerade in Gebieten mit sehr geringen Übertragungsraten Massenimpfungen in Betracht gezogen werden sollten.
Für den Fall, dass ein Malariaimpfstoff, wie der derzeitig vielversprechendste Malariaimpfstoffkandidat RTS,S zugelassen und gebrauchsfertig sein sollte, gilt die Verteilung und Verabreichung des Impfstoffs an drei Monate alte Säuglinge im Rahmen des bestehenden Expanded Programme on Immunization (EPI) der WHO als am wirkungsvollsten. Dies gilt für Gebiete, in denen es eine hohe Malariaübertragung gibt. Im Rahmen einer neuen Studie haben Forscher nun gezeigt, dass gerade in Gebieten mit niedrigeren Malariaübertragungsraten Massenimpfungen alle fünf Jahre besonders wirkungsvoll sind.
In a modelling study led by Thomas Smith from the Swiss Tropical and Public Health Institute in Basel, Switzerland, and published in this week’s PLoS Medicine, the authors used 14 different models that simulated the transmission of the parasite that causes malaria (Plasmodium falciparum) in thousands of hypothetical individuals through different stages of malaria infection. The authors used each model to predict the health benefits over 14 years of the potential malaria vaccine RTS,S given by different vaccination strategies and found that the predicted benefits of giving the malaria vaccine using the EPI strategy were modest and similar over a wide-range of settings. However, EPI with an initial catch-up phase averted the most deaths per vaccine dose in individuals who had over 10 infectious malaria bites a year but in areas where people typically have two or less infectious mosquito bites a year, the authors’ model found that mass vaccination strategies substantially reduced transmission leading to much greater health effects per dose than other strategies, even at modest coverage.
This study only reports the first stages of using ensemble modelling to predict the health effects of RTS,S vaccination, so future studies will need to combine the outputs of multiple models with economic analyses to provide a rational basis for the design of vaccine-containing malaria control and elimination programs.
The authors say: “The ensemble modeling approach provides more robust outcomes than single models, and our analyses suggest that such an approach produces greater confidence in predictions of health effects for lower malaria transmission settings than for higher ones.”
The authors continue: “This study suggests that targeted mass vaccination with RTS,S in low transmission settings may be more efficient than national-level introduction via EPI programs, but there remains a need to analyze the feasibility and economics of such strategies and the circumstances in which vaccination will avert epidemics.”
Link: doi:10.1371/journal.pmed.1001157
Kontakt:
Prof. Dr. Thomas Smith
Swiss Tropical and Public Health Institute
Socinstrasse 57
Basel, CH 4002
Switzerland
+41 (0) 61-284 8273
thomas-a.smith@unibas.ch
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