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The potential impact of immunization campaign budget re-allocation on global eradication of paediatric infectious diseases.

Fitzpatrick T, Bauch CT - BMC Public Health (2011)

Bottom Line: However, mathematical modeling is required to understand the potential extent of this effect.We also find that the time to eradication of all three diseases is not necessarily lowest when the least transmissible disease is targeted first.Relatively modest differences in budget allocation strategies in the near-term can result in surprisingly large long-term differences in time required to eradicate, as a result of the amplifying effects of herd immunity and the nonlinearities of disease transmission.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Mathematics and Statistics, University of Guelph, Canada.

ABSTRACT

Background: The potential benefits of coordinating infectious disease eradication programs that use campaigns such as supplementary immunization activities (SIAs) should not be over-looked. One example of a coordinated approach is an adaptive "sequential strategy": first, all annual SIA budget is dedicated to the eradication of a single infectious disease; once that disease is eradicated, the annual SIA budget is re-focussed on eradicating a second disease, etc. Herd immunity suggests that a sequential strategy may eradicate several infectious diseases faster than a non-adaptive "simultaneous strategy" of dividing annual budget equally among eradication programs for those diseases. However, mathematical modeling is required to understand the potential extent of this effect.

Methods: Our objective was to illustrate how budget allocation strategies can interact with the nonlinear nature of disease transmission to determine time to eradication of several infectious diseases under different budget allocation strategies. Using a mathematical transmission model, we analyzed three hypothetical vaccine-preventable infectious diseases in three different countries. A central decision-maker can distribute funding among SIA programs for these three diseases according to either a sequential strategy or a simultaneous strategy. We explored the time to eradication under these two strategies under a range of scenarios.

Results: For a certain range of annual budgets, all three diseases can be eradicated relatively quickly under the sequential strategy, whereas eradication never occurs under the simultaneous strategy. However, moderate changes to total SIA budget, SIA frequency, order of eradication, or funding disruptions can create disproportionately large differences in the time and budget required for eradication under the sequential strategy. We find that the predicted time to eradication can be very sensitive to small differences in the rate of case importation between the countries. We also find that the time to eradication of all three diseases is not necessarily lowest when the least transmissible disease is targeted first.

Conclusions: Relatively modest differences in budget allocation strategies in the near-term can result in surprisingly large long-term differences in time required to eradicate, as a result of the amplifying effects of herd immunity and the nonlinearities of disease transmission. More sophisticated versions of such models may be useful to large international donors or other organizations as a planning or portfolio optimization tool, where choices must be made regarding how much funding to dedicate to different infectious disease eradication efforts.

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Time series of prevalence under sequential strategy. Predicted disease prevalence in India (a), Nigeria (b), and Afghanistan (c), such that routine vaccination is introduced in 1960, SIAs begin in 1990, and reallocation occurs according to the sequential strategy in 2010, eradicating diseases in the order: A, B, then C. Cumulative incidence for India (d), Nigeria (e), and Afghanistan (f) is also shown for the same scenario.
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Figure 2: Time series of prevalence under sequential strategy. Predicted disease prevalence in India (a), Nigeria (b), and Afghanistan (c), such that routine vaccination is introduced in 1960, SIAs begin in 1990, and reallocation occurs according to the sequential strategy in 2010, eradicating diseases in the order: A, B, then C. Cumulative incidence for India (d), Nigeria (e), and Afghanistan (f) is also shown for the same scenario.

Mentions: In the case of the sequential strategy with the same annual budget of US $180 million, the time evolution is the same as for the simultaneous strategy until budget reallocation begins in 2010. Under the sequential strategy, the model predicts a very different time evolution of future incidence (Figure 2). All three diseases are eradicated by 2030: Disease A is eradicated first in 2021, followed by Disease B in 2024, and finally Disease C in 2030 (by comparison, under the simultaneous strategy for the same budget, no disease is eradicated in the foreseeable future). Figure 3 shows a time series of SIA vaccination coverage in each country under the sequential strategy, and the changing vaccine coverage due to budget re-allocation is apparent.


The potential impact of immunization campaign budget re-allocation on global eradication of paediatric infectious diseases.

Fitzpatrick T, Bauch CT - BMC Public Health (2011)

Time series of prevalence under sequential strategy. Predicted disease prevalence in India (a), Nigeria (b), and Afghanistan (c), such that routine vaccination is introduced in 1960, SIAs begin in 1990, and reallocation occurs according to the sequential strategy in 2010, eradicating diseases in the order: A, B, then C. Cumulative incidence for India (d), Nigeria (e), and Afghanistan (f) is also shown for the same scenario.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3198942&req=5

Figure 2: Time series of prevalence under sequential strategy. Predicted disease prevalence in India (a), Nigeria (b), and Afghanistan (c), such that routine vaccination is introduced in 1960, SIAs begin in 1990, and reallocation occurs according to the sequential strategy in 2010, eradicating diseases in the order: A, B, then C. Cumulative incidence for India (d), Nigeria (e), and Afghanistan (f) is also shown for the same scenario.
Mentions: In the case of the sequential strategy with the same annual budget of US $180 million, the time evolution is the same as for the simultaneous strategy until budget reallocation begins in 2010. Under the sequential strategy, the model predicts a very different time evolution of future incidence (Figure 2). All three diseases are eradicated by 2030: Disease A is eradicated first in 2021, followed by Disease B in 2024, and finally Disease C in 2030 (by comparison, under the simultaneous strategy for the same budget, no disease is eradicated in the foreseeable future). Figure 3 shows a time series of SIA vaccination coverage in each country under the sequential strategy, and the changing vaccine coverage due to budget re-allocation is apparent.

Bottom Line: However, mathematical modeling is required to understand the potential extent of this effect.We also find that the time to eradication of all three diseases is not necessarily lowest when the least transmissible disease is targeted first.Relatively modest differences in budget allocation strategies in the near-term can result in surprisingly large long-term differences in time required to eradicate, as a result of the amplifying effects of herd immunity and the nonlinearities of disease transmission.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Mathematics and Statistics, University of Guelph, Canada.

ABSTRACT

Background: The potential benefits of coordinating infectious disease eradication programs that use campaigns such as supplementary immunization activities (SIAs) should not be over-looked. One example of a coordinated approach is an adaptive "sequential strategy": first, all annual SIA budget is dedicated to the eradication of a single infectious disease; once that disease is eradicated, the annual SIA budget is re-focussed on eradicating a second disease, etc. Herd immunity suggests that a sequential strategy may eradicate several infectious diseases faster than a non-adaptive "simultaneous strategy" of dividing annual budget equally among eradication programs for those diseases. However, mathematical modeling is required to understand the potential extent of this effect.

Methods: Our objective was to illustrate how budget allocation strategies can interact with the nonlinear nature of disease transmission to determine time to eradication of several infectious diseases under different budget allocation strategies. Using a mathematical transmission model, we analyzed three hypothetical vaccine-preventable infectious diseases in three different countries. A central decision-maker can distribute funding among SIA programs for these three diseases according to either a sequential strategy or a simultaneous strategy. We explored the time to eradication under these two strategies under a range of scenarios.

Results: For a certain range of annual budgets, all three diseases can be eradicated relatively quickly under the sequential strategy, whereas eradication never occurs under the simultaneous strategy. However, moderate changes to total SIA budget, SIA frequency, order of eradication, or funding disruptions can create disproportionately large differences in the time and budget required for eradication under the sequential strategy. We find that the predicted time to eradication can be very sensitive to small differences in the rate of case importation between the countries. We also find that the time to eradication of all three diseases is not necessarily lowest when the least transmissible disease is targeted first.

Conclusions: Relatively modest differences in budget allocation strategies in the near-term can result in surprisingly large long-term differences in time required to eradicate, as a result of the amplifying effects of herd immunity and the nonlinearities of disease transmission. More sophisticated versions of such models may be useful to large international donors or other organizations as a planning or portfolio optimization tool, where choices must be made regarding how much funding to dedicate to different infectious disease eradication efforts.

Show MeSH
Related in: MedlinePlus