Limits...
Vaccination against foot-and-mouth disease: do initial conditions affect its benefit?

Porphyre T, Auty HK, Tildesley MJ, Gunn GJ, Woolhouse ME - PLoS ONE (2013)

Bottom Line: In particular, we tested whether changes in the location of the incursion and the delay of implementation would affect the epidemiological benefit of such a policy in the context of Scotland.The results show that the decision to vaccinate, or not, is not straightforward and strongly depends on the underlying local structure of the population-at-risk.However, if a decision to vaccinate is made, we show that delaying its implementation in the field may markedly reduce its benefit.

View Article: PubMed Central - PubMed

Affiliation: Epidemiology Group, Centre for Immunity, Infection and Evolution, University of Edinburgh, Ashworth Laboratories, Edinburgh, United Kingdom.

ABSTRACT
When facing incursion of a major livestock infectious disease, the decision to implement a vaccination programme is made at the national level. To make this decision, governments must consider whether the benefits of vaccination are sufficient to outweigh potential additional costs, including further trade restrictions that may be imposed due to the implementation of vaccination. However, little consensus exists on the factors triggering its implementation on the field. This work explores the effect of several triggers in the implementation of a reactive vaccination-to-live policy when facing epidemics of foot-and-mouth disease. In particular, we tested whether changes in the location of the incursion and the delay of implementation would affect the epidemiological benefit of such a policy in the context of Scotland. To reach this goal, we used a spatial, premises-based model that has been extensively used to investigate the effectiveness of mitigation procedures in Great Britain. The results show that the decision to vaccinate, or not, is not straightforward and strongly depends on the underlying local structure of the population-at-risk. With regards to disease incursion preparedness, simply identifying areas of highest population density may not capture all complexities that may influence the spread of disease as well as the benefit of implementing vaccination. However, if a decision to vaccinate is made, we show that delaying its implementation in the field may markedly reduce its benefit. This work provides guidelines to support policy makers in their decision to implement, or not, a vaccination-to-live policy when facing epidemics of infectious livestock disease.

Show MeSH

Related in: MedlinePlus

Resilience of vaccination benefit to delays in field implementation.(A) Map showing the location of Aberdeenshire and Ayrshire as examples for the different dynamics identified in Scotland. (B) Effect of delaying the implementation of vaccination in the field on its benefit (VB) for epidemics generated from a single premise in Ayrshire (red) and Aberdeenshire (blue). (C) Risk ratio in VB for each infected premise (IP) increase prior to first detection. (D) Variations in the rate of VB loss for each day increase in delaying its implementation in the field. Values of VB in B, C and D were computed over the number of IP (dark symbols) and the duration (light symbols) of generated epidemics. The probability of severe epidemics was defined as the probability of epidemics either showing >100 IPs (dark symbols) or lasting >60 days (light symbols). Grey dashed line in B indicates the  benefit. Note that x-axis in B are in log-scale.
© Copyright Policy
Related In: Results  -  Collection


getmorefigures.php?uid=PMC3815046&req=5

pone-0077616-g005: Resilience of vaccination benefit to delays in field implementation.(A) Map showing the location of Aberdeenshire and Ayrshire as examples for the different dynamics identified in Scotland. (B) Effect of delaying the implementation of vaccination in the field on its benefit (VB) for epidemics generated from a single premise in Ayrshire (red) and Aberdeenshire (blue). (C) Risk ratio in VB for each infected premise (IP) increase prior to first detection. (D) Variations in the rate of VB loss for each day increase in delaying its implementation in the field. Values of VB in B, C and D were computed over the number of IP (dark symbols) and the duration (light symbols) of generated epidemics. The probability of severe epidemics was defined as the probability of epidemics either showing >100 IPs (dark symbols) or lasting >60 days (light symbols). Grey dashed line in B indicates the benefit. Note that x-axis in B are in log-scale.

Mentions: When investigating the effect of delaying the field implementation of vaccination on its benefit, we restrict our analyses to incursions occurring either in Ayrshire or in Aberdeenshire. These counties were chosen since they are both areas with a high density of premises and animals and represent good examples of the different patterns seen in the southern and northern counties of Scotland (Figure 5A). For both counties, highest VB values were obtained when no delay in implementing the policy occurs (Figure 5B). Obviously this has marked implications when incursions occur in Aberdeenshire, where implementing vaccination shows inherently little benefit. Indeed, waiting 10 days to implement the policy would produce little additional epidemiological benefit for Aberdeenshire incursions, as most epidemics would be finished (Figure 5B, Table 1). Again, vaccination is of most value in reducing the extent of severe epidemics (Figure 3). This means that vaccination is still beneficial for Ayrshire incursions (where the risk of severe epidemics is higher) even if there is a large delay in implementation (Figure 5B).


Vaccination against foot-and-mouth disease: do initial conditions affect its benefit?

Porphyre T, Auty HK, Tildesley MJ, Gunn GJ, Woolhouse ME - PLoS ONE (2013)

Resilience of vaccination benefit to delays in field implementation.(A) Map showing the location of Aberdeenshire and Ayrshire as examples for the different dynamics identified in Scotland. (B) Effect of delaying the implementation of vaccination in the field on its benefit (VB) for epidemics generated from a single premise in Ayrshire (red) and Aberdeenshire (blue). (C) Risk ratio in VB for each infected premise (IP) increase prior to first detection. (D) Variations in the rate of VB loss for each day increase in delaying its implementation in the field. Values of VB in B, C and D were computed over the number of IP (dark symbols) and the duration (light symbols) of generated epidemics. The probability of severe epidemics was defined as the probability of epidemics either showing >100 IPs (dark symbols) or lasting >60 days (light symbols). Grey dashed line in B indicates the  benefit. Note that x-axis in B are in log-scale.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3815046&req=5

pone-0077616-g005: Resilience of vaccination benefit to delays in field implementation.(A) Map showing the location of Aberdeenshire and Ayrshire as examples for the different dynamics identified in Scotland. (B) Effect of delaying the implementation of vaccination in the field on its benefit (VB) for epidemics generated from a single premise in Ayrshire (red) and Aberdeenshire (blue). (C) Risk ratio in VB for each infected premise (IP) increase prior to first detection. (D) Variations in the rate of VB loss for each day increase in delaying its implementation in the field. Values of VB in B, C and D were computed over the number of IP (dark symbols) and the duration (light symbols) of generated epidemics. The probability of severe epidemics was defined as the probability of epidemics either showing >100 IPs (dark symbols) or lasting >60 days (light symbols). Grey dashed line in B indicates the benefit. Note that x-axis in B are in log-scale.
Mentions: When investigating the effect of delaying the field implementation of vaccination on its benefit, we restrict our analyses to incursions occurring either in Ayrshire or in Aberdeenshire. These counties were chosen since they are both areas with a high density of premises and animals and represent good examples of the different patterns seen in the southern and northern counties of Scotland (Figure 5A). For both counties, highest VB values were obtained when no delay in implementing the policy occurs (Figure 5B). Obviously this has marked implications when incursions occur in Aberdeenshire, where implementing vaccination shows inherently little benefit. Indeed, waiting 10 days to implement the policy would produce little additional epidemiological benefit for Aberdeenshire incursions, as most epidemics would be finished (Figure 5B, Table 1). Again, vaccination is of most value in reducing the extent of severe epidemics (Figure 3). This means that vaccination is still beneficial for Ayrshire incursions (where the risk of severe epidemics is higher) even if there is a large delay in implementation (Figure 5B).

Bottom Line: In particular, we tested whether changes in the location of the incursion and the delay of implementation would affect the epidemiological benefit of such a policy in the context of Scotland.The results show that the decision to vaccinate, or not, is not straightforward and strongly depends on the underlying local structure of the population-at-risk.However, if a decision to vaccinate is made, we show that delaying its implementation in the field may markedly reduce its benefit.

View Article: PubMed Central - PubMed

Affiliation: Epidemiology Group, Centre for Immunity, Infection and Evolution, University of Edinburgh, Ashworth Laboratories, Edinburgh, United Kingdom.

ABSTRACT
When facing incursion of a major livestock infectious disease, the decision to implement a vaccination programme is made at the national level. To make this decision, governments must consider whether the benefits of vaccination are sufficient to outweigh potential additional costs, including further trade restrictions that may be imposed due to the implementation of vaccination. However, little consensus exists on the factors triggering its implementation on the field. This work explores the effect of several triggers in the implementation of a reactive vaccination-to-live policy when facing epidemics of foot-and-mouth disease. In particular, we tested whether changes in the location of the incursion and the delay of implementation would affect the epidemiological benefit of such a policy in the context of Scotland. To reach this goal, we used a spatial, premises-based model that has been extensively used to investigate the effectiveness of mitigation procedures in Great Britain. The results show that the decision to vaccinate, or not, is not straightforward and strongly depends on the underlying local structure of the population-at-risk. With regards to disease incursion preparedness, simply identifying areas of highest population density may not capture all complexities that may influence the spread of disease as well as the benefit of implementing vaccination. However, if a decision to vaccinate is made, we show that delaying its implementation in the field may markedly reduce its benefit. This work provides guidelines to support policy makers in their decision to implement, or not, a vaccination-to-live policy when facing epidemics of infectious livestock disease.

Show MeSH
Related in: MedlinePlus