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Vaccination - What exactly do they mean?

by 5m Editor
1 January 2001, at 12:00am

The dreaded 'V' word is now being banded around freely by the UK Government, who only a few weeks ago were stating it was the option of "last resort". Have things got that bad? - Jim Muirhead, Editor of thePigSite.com looks at the facts and highlights some of the reasons behind the indecision.

At first the Governments change in heart could appear rather contradictory, however it is important to understand there are different vaccination protocols that could be employed, and to date these have not being properly explained.

To vaccinate or not to vaccinate?

EU policy is against general/widespread vaccination and there are several good reasons for this.
  1. Vaccines have their inadequacies: A vaccine needs to match the strain of disease in question and does not provide immunity against other strains. As there are several strains, vaccination, even with a multi-strain vaccine, would not guarantee complete immunity from the disease.
  2. Sheer cost: There are literally hundreds of millions of susceptible animals in EU. At least 70% of animals would need to be vaccinated every six to nine months to maintain a level of immunity to prevent a major outbreak. This scale of vaccination would be hugely expensive and as already noted, would still not guarantee full protection.
  3. Vaccinated animals can be carriers: Once vaccinated an animal becomes immune to the disease, however should that animal come into contact with the virus it can 'carry' it and spread it to non-immunised animals. These animals would then catch the disease and have to be slaughtered out. Additionally, current vaccines provide limited immunity in pigs, which also provide the perfect means of spreading the disease.
  4. Lack of distinction: Although it is possible to distinguish antibodies from vaccinated animals and those that have been infected, when a vaccinated animal becomes infected this distinction is usually lost. Thus it is difficult to be sure a vaccinated animal has not come into contact with the disease and is thus a carrier with the potential to spread the disease.
For the reasons above, under international rules the introduction of a general vaccination policy would close off EU exports of all livestock and meat products to FMD-free countries including the USA, Canada and Japan. It would also require the EU to be free from FMD for possibly up to two years following the cessation of general vaccination to regain its FMD-free status.

It is for these reason why both the UK Government and the European Union have previously stated that vaccination was a last resort.

Emergency vaccination

Since then however, the Dutch have had 5 outbreaks and convinced the EU to allow them to Emergency vaccinate. This, along with the ongoing crisis, has prompted the UK Government to review it's policy. So what's the difference?

Emergency vaccination, also called ring vaccination is a process where only the animals around an outbreak are vaccinated, to a depth of say 3km. The vaccine inoculates the animals most in danger and helps to limit the spread of the virus. This helps create a barrier or what has been termed a 'firebreak' around the outbreak while the slaughter process is dealt with.

Used in this fashion emergency vaccination can have a role play and be an effective method for limiting the spread of the disease in isolated cases. Additionally, provided the policy includes the subsequent slaughter of the vaccinated animals, which is the economic key, this process negates most of the problems of general vaccination;
  • Only a relative few animals need to be vaccinated
  • the vaccine need only match the strain involved. Additionally,
  • only one shot of vaccine would probably be required.

But what about those trade restrictions?

This is where the official definition of an FMD-free region or country comes in. Following an outbreak in an FMD-free country, it is necessary (amongst other requirements) to be outbreak free for a period of three months to regain your FMD-free status. If a general vaccination policy is in place this period is currently 12 months but may soon be increased to 24 months. However, the definition allows a 3 month return period (subject to a few other criteria) if the vaccinated animals are slaughtered. Therefore emergency vaccination need not increase the trade penalties beyond those already imposed due to the outbreak itself.

Thus it is possible to use emergency vaccination to help control the disease prior to the animals adjacent to an outbreak being slaughtered. This is what the Dutch are doing, and will probably be what the Germans and other Europeans will do should they also suffer an outbreak.

Muddied UK Picture

In the UK however the picture is not so clear. For emergency vaccination to be effective there has to be no animal movements beyond the vaccinated area. As the UK outbreak was identified in several areas of the UK within a few days of confirmation, emergency vaccination could not have controlled the national spread. That does not mean however, it could not be used as a benefit now. The probable reason the Government is dithering is two fold.
  1. The Governments control policy is one of radial culls around outbreaks with an aim of getting all affected animals slaughtered and disposed of within 24 hour periods. As the vaccine takes a minimum 3 days to become effective and probably longer, it would be redundant if the policy aims are achieved.
  2. There is no clear picture of where to vaccinate due to the widespread nature of the outbreak. This would lead to large areas and numbers of animals needing to be vaccinated. Good logistics will be needed to distribute and administer the vaccines. Tight reporting and identification procedures will be required to document the process and ensure that all the vaccinated animals are subsequently slaughtered. Following the mass cull debacle the Government is most likely keen to have all the pieces of the jigsaw in place before making any formal announcement.

Action needed now

Emergency vaccination could be introduced then as part of a strategic plan. For instance, mass culls are planned around Cumbria to get on top of the disease, but these are simply not happening due to the backlog of infections. The healthy animals in this area designated for slaughter could be vaccinated. This would help to limit the potential spread in the interim period and help to speed up the control process.

The Dutch have highlighted that emergency vaccination is an additional tool that could be used against this disease without the drastic economic implications of general vaccination. It may not be a perfect solution and have it's pitfalls, but any weapon that can be used to help control this dreadful disease must surely be used.

Provided vaccination is used in this way as part of the control strategy it is likely farmers leaders will now be behind the policy. However a policy that includes general vaccination would effectively rule the UK and possibly Europe out of the livestock and meat export market for probably two years and would be much more difficult to get agreement on both at home and in Europe.

Even though the picture is not so clear in the UK, if action is to be taken, the sooner the better.


Additional information on Foot-and-Mouth disease plus up-to-date news on UK, European and World outbreaks can be found at www.thePigSite.com