1. Emergency vaccination benefits ERADICATION of hypothetical introductions of FMD inTO New Zealand
By Kylee Walker on behalf of:
Zhidong Yu, Robert Sanson, Thomas Rawdon, Katie Owen, Katie Hickey, Mary van Andel.
This talk will focus on a subset of the outputs from a piece of modelling work to evaluate the benefits of emergency vaccination for hypothetical introductions of FMD into New Zealand. This work was conducted as part of New Zealand’s readiness programme to prepare for effective and rapid eradication of FMD should it occur to New Zealand. I’ll present on behalf of these authors who are not able to attend the conference.

2. Impact of FMD outbreak in New Zealand
Never had a case of FMD so we know little about how an outbreak would behave in the New Zealand setting
Catastrophic for the country
Market shutdown for animal and animal products
Loss of $16.2bn over 8 years
Damage in life style, reputation and many other factors
New Zealand has never had a case of FMD. As a result we know little on how it might spread should it arrive. What we do know is that an outbreak of FMD in NZ would be catastrophic for our economy and people’s life due to our extraordinary reliance on international trade of animals and animal products for our economy.
A separate piece of work on macroeconomic modelling indicated a loss of $16 billion over 8 years. The real Gross Domestic Production would shrank by 7.8% for the first year. An outbreak would badly affect the life of many and lead to serious damage to New Zealand’s reputation in biosecurity, environment and animal welfare.

3. FMD response policy in New Zealand
Readiness to response primarily relied on stamping-out
New policy: considers vaccination as an adjunct tool from the start of an outbreak
For many years New Zealand’s response policy to FMD incursion was primarily relying on stamping-out with vaccination as the very last choice.
New Zealand has reviewed this policy in light of the progress made in controlling FMD using vaccination, increased animal welfare concerns and further analysis on the pros and cos in using vaccination.
The macro-economic modelling indicated that using vaccination as an additional disease management tool could significantly reduce the overall loss. This work and close interaction with the key industry sectors directly affected by FMD led to adoption of a new FMD vaccination policy which considers using vaccination to minimise the loss from the start of an FMD outbreak.

4. Purpose of the study
Verify benefits of vaccination with extended scenarios
Understand the key factors affecting the effectiveness of vaccination
Suggest a practical vaccination strategy based on resources available
Identify new areas for future study
The aims of this work were three folds:
Verify benefits of vaccination with extended scenarios in New Zealand
understand the key factors affecting the effectiveness of vaccination under New Zealand context of farming, FMD response policy and assume performance of stamping-out and vaccination
assessing a practical vaccination strategy based resources available
Identify new areas for future study to assist vaccination decision-making.

5. Study design (1) Output indicators: Three introduction scenarios:
Infected Premises (IP) numbers
Outbreak duration (days)
Area size under control (AUC)
Three introduction scenarios:
Auckland, Taranaki and Christchurch
Two levels of stamping-out efficacy (compliance rates):
Standard Stamping Out vs
Reduced Stamping Out
Two vaccination efficacy (herd immunity) settings.
InterSpred Plus (ISP) was used in this study. Farm and animal information were derived from AgriBase database.
The efficacy of responding to FMD using SO alone was used as the basis for assessing the additional effect of vaccination. Overall both personnel and vaccine resources were assumed to be unlimited.
The primary outputs from this study are IP numbers, duration and area under control for each outbreak. AUC represented the combined areas affected by the 10 km zones of intensive movement control (surveillance zone), derived by generating 10 km radius zones around all IPs, dissolving the resulting polygons to resolve overlaps and then calculating the combined areas in km2.
Three defined hypothetical introduction scenarios were used. They include South Auckland, Taranake and Canterbury. These are key animal farming areas in New Zealand representing by high density of farms. These introductory scenarios represented differences in farm types, farm density and plausible ways how FMD would be introduced into and detected in NZ.
- A simultaneous incursion in 2 lifestyle blocks with pigs in S. Auckland represent represents an biosecurity attach. Detection is by passive surveillance.
- Introduction in a small pig farm in Taranaki is also detected by passive surveillance.
- The introduction in a sheep farm in South Canterbury represents an 18 days delayed detection.
Two levels of stamping-out efficacy and vaccination efficacy were modelled. High risk and medium risk movement compliance rates were dropped slightly to present less desirable (reduced) SO compliance. High herd immunity setting represent complete resistance to infection six days after vaccination while susceptibility remained at 5% all the time from Day 6 post vaccination.

6. Study design (2) Multiple factors (strategies, start time, etc):
Starting time: 11, 14, 16, 21, 28 days PD or 50 /100 IPs
SV and PV with variable zone sizes
Cattle-only (Taranaki Only)
Impact of personnel resource
Multiple factors relevant to vaccination efficacy were tested. These include
- Different vaccination starting time: 11, 14, 16, 21, 28 days after confirmation of outbreak or when IP reached 50 /100
- Suppressive vaccination (SV) and Protective vaccination (PV) with different vaccination zone sizes. SV is conducted with zone size of 1.5, 3 and 5 km radius in areas immediately surrounding an IP to suppress further outbreak, while PV strategy vaccinated those herds which were separated to an IP by a buffer zone. These buffer zones were 3, 4 or 5 km in diameter. The vaccination area increased with larger buffered zone despite of the same band width.
- Cattle-only vaccination where no other animals apart from cattle are vaccinated was only tested in Taranake.
The impact of personal resources were assessed by varying the resource available to complete vaccination certain number of farms using Taranaki scenarios.
Vaccination priority: ‘outer-to-inner’ for SVs and ‘inner-to-outer’ for PV.
Vaccine applied to all IPs 7 days retrospectively* until eradication
100 iterations for each model configuration
Simulations ran until eradication or stopped after 365 / 180 days for SO / SO + vaccination
Suppressive vaccination
Protective vaccination

7. Effect of vaccination start timeIP
Duration
Area under control
I will only present a subset of the data here and then summarise the overall results. These boxplots compare the number of IPs, duration and area under control for the different start dates of a 3 km suppressive vaccination (SV) zone with a standard stamping-out programme (“0d”), for a Taranaki incursion with airborne spread included. Y axis is IP numbers, epidemic duration in days and areas under control respectively. Vaccination prevents the run-away epidemics and led to significantly lower medians when compared to the SO only programme. Earlier vaccination shows greater reduction. Despite still better than SO alone vaccination was significantly less effective if vaccination starts after IP number hits 50 or 100 IPs.

8. Effect of vaccination strategy and zone sizeIP
Duration
Area under control
These three boxplots compare the number of IPs, duration and area under control for the different types and sizes of vaccination zone compared to a standard stamping-out programme (SO) in Taranaki incursions with airborne spread included (vaccination started on Day 11 after first detection). Overall larger vaccination zone (5, 3 and 1.5 km radius) of SV led to better disease control km PV were even more effective at the expense of both human and vaccine resources.

9. Vaccine dose requirements
The number of vaccine doses used increased markedly as the PV zone sizes increased from 1.5 km to 5 km. This was related to the rapid increase in the area of circular zones by the square of the radius and the rapid increase in the number of farms and animals. Almost 500k doses of vaccines are required for 5-10km PV. Fro scenarios where vaccination starts at Day 11 post detection, vaccine dose for 5-10km PV is approximately 5, 3.5 or 2.5 times more than the other three SV vaccination situations showed in the graph. Large doses of vaccine are required when vaccination is instigated later.

10. Effects of personnel resource on vaccination
y ~ (1/x)
y ~ (1/x)
R2 = 86%
R2 = 78%
These plots are showing the relationship between IP numbers and duration against number of farms that could be vaccinated per day. They indicates that the optimal number of farms required to be vaccinated per day is about 200, with little additional benefit to increasing resources above this threshold for the Taranake scenarios modelled. Below this level, both the numbers of IPs and epidemic duration increased markedly. It is important to point out for larger outbreaks personnel resource requirement is expected to be larger.

11. Key findings summarised
Prevented run-away epidemics and aided control
More effective when used early
More beneficial for larger outbreaks
Better effect for larger vaccination zone
Personnel and vaccine resources influenced outcomes
Cattle-only vaccination promising
Vaccination prevented run-away epidemics and reduced the outbreak size.
It was more effective when used earlier.
More effective for larger outbreaks. Therefore a early call on the potential outbreak situation would be essential for making a robust decision on if or not to use vaccination.
Increased vaccination zone size showed more desirable effect in disease control at the expense of personnel and vaccine resources. The better effect of Protective vaccination over Suppressive vaccination was primarily explained by the increased zone size.
Resources, both personnel and vaccine, could influence the performance of vaccination. It is critical to bring them into consideration when deciding on vaccination strategies.
Cattle-only vaccination was found to be promising in assisting outbreak control. But there are higher uncertainty on the results for two reasons: the data were only derived from scenarios in Taranake and they based on proportion of animals (cattle) to be vaccinated in farms with mixed populations. More work is required to substantiate this finding.

12. Key factors influencing vaccination effects
Air transmission
Incursion scenario (location and detection settings)
Incursion detection time
Vaccination start day
Herd immunity setting
The key factors affecting the vaccination efficacy are: with or without air transmission, incursion scenarios which representing both location of introduction and detection settings, how soon the incursion was found, the time to start vaccination and the level of herd immunity can be achieved by a vaccination programme.
The small reduction in the compliance rates of the control for high and medium risk movements were not found to have significant impact on vaccination. This may simply indicate that the difference allowed in this study wasn’t large enough to cause significant difference. There is no doubt that maintaining effective SO measures are essential for control of an FMD outbreak.

13. Conclusions
Findings consistent with many early studies - vaccination could benefit disease control in New Zealand
3-5 km PV starting from Day recommended
The results from this work are consistent with many studies conducted overseas and our collaborative work with Australia, Canada, UK and the united states.
It demonstrated that using vaccination as an additional tool would aid control should an FMD outbreak occur n New Zealand.
Based on the information obtained so far and our understanding of key factors affect the effectiveness of emergency vaccination as an additional tool in responding to a possible outbreak in New Zealand, protective vaccination with 3-5 km diameter starting at Day post confirmation of outbreak is recommended.

14. Future studies
Recommended further studies to support vaccination decision-making:
cattle-only vaccination,
personnel resource requirements, and
early indicators for potential large outbreaks.
We recommend further studies to provide more information to assist vaccination decision-making. They include the effect of cattle-only vaccination, personnel resources requirements with and without vaccination and early indicators which can be used to make better calls on the potential size of an outbreak at the earliest stage. Insights from these studies will support the important, but difficult decision when the benefits of vaccination in disease control has to be balanced with potential delays in resuming trade under the current OIE policy.

15. Acknowledgements
Andre van Halderen: Contribution in macro-economic modelling and general advice for this study.