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Evaluating the costeffectiveness of vaccination programmes: A dynamic perspective
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UNSPECIFIED (1999) Evaluating the costeffectiveness of vaccination programmes: A dynamic perspective. STATISTICS IN MEDICINE, 18 (23). pp. 32633282. ISSN 02776715.
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Abstract
Although there are many models which are used to calculate the health benefits (and thus the costeffectiveness) of vaccination programmes, they can be divided into two groups: those which assume a constant force of infection, that is a constant persusceptible rate of infection; and those which assume that the force of infection (at time t) is a function of the number of infectious individuals in the population at that time (dynamic models). In constant force of infection models the persusceptible rate of infection is not altered, whereas in dynamic models mass immunization results in fewer infectious individuals in the community and thus a lower force of infection acting on those who were not immunized. We take an example of each of these types of model examine their underlying assumptions and compare their predictions of the costeffectiveness of a mass immunization programme against a hypothetical close contact infection, such as measles. We show that if cases of infection are the outcome of interest then the constant force of infection model will always underestimate the costeffectiveness of the immunization programme except at the extremes when no one or everyone is immunized. However, unlike the constant force of infection model, the dynamic model predicts an increase in the average age at infection after immunization which could impact on the estimate of the costeffectiveness of the programme if the risk of developing serious disease is a function of the age at infection (as, for instance, is the case for congenital rubella syndrome). Taking cases of infection as the outcome measure and using the dynamic model, the undiscounted costeffectiveness ratio will tend to decline over time and approach a constant value, as the system moves from pre to postimmunization equilibrium. We go on to show how the costeffectiveness of a fixedterm immunization programme might change over time, and discuss why, under most circumstances, decision makers should not assume that elimination (permitting termination of mass immunization) will occur. Copyright (C) 1999 John Wiley & Sons, Ltd.
Item Type:  Journal Article  

Subjects:  Q Science > QH Natural history > QH301 Biology R Medicine > RA Public aspects of medicine > RA0421 Public health. Hygiene. Preventive Medicine R Medicine Q Science > QA Mathematics 

Journal or Publication Title:  STATISTICS IN MEDICINE  
Publisher:  JOHN WILEY & SONS LTD  
ISSN:  02776715  
Official Date:  15 December 1999  
Dates: 


Volume:  18  
Number:  23  
Number of Pages:  20  
Page Range:  pp. 32633282  
Publication Status:  Published 
Data sourced from Thomson Reuters' Web of Knowledge
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