Thursday, August 02, 2012

Study: Vaccination and waning immunity.


 2009 Jun 7;276(1664):2071-80. Epub 2009 Mar 4.

Implications of vaccination and waning immunity.

Source

Department of Mathematics, York University, N520 Ross Building, 4700 Keele Street, Toronto, Ontario, Canada M3J 1P3. jmheffer@mathstat.yorku.ca

Abstract

For infectious diseases where immunization can offer lifelong protection, a variety of simple models can be used to explain the utility of vaccination as a control method. However, for many diseases, immunity wanes over time and is subsequently enhanced (boosted) by asymptomatic encounters with the infection. The study of this type of epidemiological process requires a model formulation that can capture both the within-host dynamics of the pathogen and immune system as well as the associated population-level transmission dynamics. Here, we parametrize such a model for measles and show how vaccination can have a range of unexpected consequences as it reduces the natural boosting of immunity as well as reducing the number of naive susceptibles. In particular, we show that moderate waning times (40-80 years) and high levels of vaccination (greater than 70%) can induce large-scale oscillations with substantial numbers of symptomatic cases being generated at the peak. In addition, we predict that, after a long disease-free period, the introduction of infection will lead to far larger epidemics than that predicted by standard models. These results have clear implications for the long-term success of any vaccination campaign and highlight the need for a sound understanding of the immunological mechanisms of immunity and vaccination.
PMID:
 
19324753
 
[PubMed - indexed for MEDLINE] 
PMCID:
 
PMC2677258
 

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