Limits...
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.

Show MeSH

Related in: MedlinePlus

SIA funding hiatus. Effect of a break in SIA funding on year of eradication under different annual budget scenarios. Funding is entirely cut (SIA vaccination coverage is 0%) for 0, 3, 6 and 9 years in either all three countries (a) or Nigeria only (b). In each case, the hiatus begins in 2016, and funding re-commences as normal after the hiatus.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC3198942&req=5

Figure 7: SIA funding hiatus. Effect of a break in SIA funding on year of eradication under different annual budget scenarios. Funding is entirely cut (SIA vaccination coverage is 0%) for 0, 3, 6 and 9 years in either all three countries (a) or Nigeria only (b). In each case, the hiatus begins in 2016, and funding re-commences as normal after the hiatus.

Mentions: As in previous simulations, there is a minimum threshold budget, below which eradication is not possible within the near future. As for the sequential strategy without budget interruption, the minimum threshold budget is $180 million and there is a sharp decline in the number of years required for eradication above this threshold. Beyond a budget of $200 million, increases in budget do not translate into significant differences in time to eradication. In these respects, the results under budget interruption are qualitatively similar to the results under no interruption. However, there are quantitative differences: the time to eradication generally increases under the budget interruption scenario. For budgets greater than the optimal budget of $200 million, interruptions of N years translate to delayed eradication by approximately N years: the baseline case with no interruption achieves eradication by 2024 under a $220 million budget; the case with a 3-year break requires 3 extra years for the same $220 million budget, the case with a 6-year break requires 6 more years for a $230 million budget, and the case with a 9-year break requires 9 more years for eradication for a $230 million budget (Figure 7a). In stark contrast, below the optimal budget of $200 million, the time to eradication increases enormously for relatively small interruptions (Figure 7a). For example, a 3-year break at a budget of $180 million delays the time to eradication of all three diseases from 2030 to 2080, and the setbacks are even greater for 6-year and 9-year breaks.


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

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

SIA funding hiatus. Effect of a break in SIA funding on year of eradication under different annual budget scenarios. Funding is entirely cut (SIA vaccination coverage is 0%) for 0, 3, 6 and 9 years in either all three countries (a) or Nigeria only (b). In each case, the hiatus begins in 2016, and funding re-commences as normal after the hiatus.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

Figure 7: SIA funding hiatus. Effect of a break in SIA funding on year of eradication under different annual budget scenarios. Funding is entirely cut (SIA vaccination coverage is 0%) for 0, 3, 6 and 9 years in either all three countries (a) or Nigeria only (b). In each case, the hiatus begins in 2016, and funding re-commences as normal after the hiatus.
Mentions: As in previous simulations, there is a minimum threshold budget, below which eradication is not possible within the near future. As for the sequential strategy without budget interruption, the minimum threshold budget is $180 million and there is a sharp decline in the number of years required for eradication above this threshold. Beyond a budget of $200 million, increases in budget do not translate into significant differences in time to eradication. In these respects, the results under budget interruption are qualitatively similar to the results under no interruption. However, there are quantitative differences: the time to eradication generally increases under the budget interruption scenario. For budgets greater than the optimal budget of $200 million, interruptions of N years translate to delayed eradication by approximately N years: the baseline case with no interruption achieves eradication by 2024 under a $220 million budget; the case with a 3-year break requires 3 extra years for the same $220 million budget, the case with a 6-year break requires 6 more years for a $230 million budget, and the case with a 9-year break requires 9 more years for eradication for a $230 million budget (Figure 7a). In stark contrast, below the optimal budget of $200 million, the time to eradication increases enormously for relatively small interruptions (Figure 7a). For example, a 3-year break at a budget of $180 million delays the time to eradication of all three diseases from 2030 to 2080, and the setbacks are even greater for 6-year and 9-year breaks.

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