FAQ: Vaccination

Is ring vaccination against CSF using a marker vaccine aneffective alternative to ring culling?

Ring vaccination against CSF has not been used in practice yet, but according to modelling studies, the answer is yes. A vaccine takes time (ca two weeks) to become fully effective in the animal, and therefore instant culling is always faster. A 2 km ring vaccination strategy is about as effective (in terms of outbreak size and duration) as a 1 km culling strategy. Wider vaccination rings are more effective and also economically interesting for large outbreaks (indicated by >10 infected farms at the end of the High Risk Period). For the epidemiological study see: Backer et al., submitted to Journal of the Royal Society Interface, June 2008. For the socio-economical aspects of CSF vaccination see: Bergevoet et al. (2007) ISBN/EAN 978-90-8615-168-4.

Does vaccination against CSF or FMD increase the risk of not-detecting seropositive animals?

Modelling studies indeed show that due to vaccination more small within-herd outbreaks occur (on vaccinated farms), because recently-vaccinated animals are not fully protected yet. These small within-herd outbreaks can be missed during the nationwide outbreak. But when the serological "end screening"(required for declaring freedom of disease) is adapted in such a way that more animals are tested on vaccinated farms, the risk of not-detecting seropositive animals at the end screening is not larger than with culling strategies. See Backer et al., submitted to Journal of the Royal Society Interface, June 2008.2

What is the principle of vaccination?

Vaccination is the administration of antigenic material (the vaccine) to produce protective immunity to a disease. Vaccines can prevent or ameliorate the effects of infection by an infectious agent. Vaccination is considered to be the most effective and cost-effective method of preventing infectious diseases. The material administrated can either be live attenuated (weakened) forms of bacteria or viruses, killed or inactivated forms of these pathogens, or purified material such as proteins or nucleic acids.

How effective is vaccination?

The efficacy (efficiency) of vaccination depends on the nature of the disease to be vaccinated against, the kind of vaccine and age and health status of the animal to be vaccinated. In general live attenuated vaccines confer better and quicker protection than inactivated (killed) vaccines.

What are the costs of vaccination?

Vaccination in general is a very cost-effective measure to prevent the outbreak or spread of infectious diseases. Costs largely depend on the type of vaccine and the costs of administering the vaccines. Usually live vaccines are less expensive than inactivated vaccines.

How are vaccinated animals marked?

A common method to mark vaccinated animals is earmarking them.

What are the risks of vaccination?

The majority of vaccines bears no specific risk for the vaccinees. However, there may be side effects with inactivated vaccines, e.g. local or systemic allergic reactions or adverse reactions to adjuvant components. Some attenuated vaccines may cause mild disease or present a risk for pregnant animals.

Why is vaccination against major diseases like FMD and CSF prohibited in the EU?

The Single European Market requires a uniform health status of European livestock. Vaccination of national cattle or pig populations against, e.g., CSF or FMD would cause major trade barriers inside Europe. In addition it would be an impediment for export to Third Countries.

What influence does vaccination have on the export market?

Vaccination of livestock against major infectious diseases would severely hamper export of these animals and their product to other Member States of the EU and to Third Countries, because countries where vaccination is practiced are not considered to be free of a disease.

Are there tests available which differentiate vaccinated from infected animals?

There are a few vaccines licensed as “marker vaccines”. They are accompanied by serological tests, which allow differentiation between infected and vaccinated animals.

How safe is food from vaccinated animals?

Food from vaccinated animals does not pose a risk for the consumer.

Under which circumstances can emergency vaccination programmes be used?

Emergency vaccination can be used when a disease outbreak gets “out of control”, i.e. there is no realistic chance to control the outbreak by culling and movement restrictions only. In the respective EU directives there are criteria laid down that allow qualified decisions to be taken on the initiation of an emergency vaccination campaign. 12

What are the consequences of emergency vaccination regarding trade, etc?

Vaccinated animals and their products are subject to trade restrictions according to EU regulations.

How can wild boar be vaccinated against CSF?

Baits containing attenuated live CSF vaccine are suitable for the prophylactic vaccination of wild boar against CSF. Vaccination campaigns – usually accompanied by hunting measures - have been shown to be effective tools for the reduction of the number of susceptible animals in an endemic area. The application of vaccination might lead to the eradication of CSF in wild boar populations.

How long does it take post vaccination to acquire immunity?

Normally it takes some days or a few weeks after vaccination for immunity to build against a pathogen. Inactivated vaccines do not replicate, and at least one booster is required after initial immunisation. Frequent revaccinations are required to keep the immune response up. In contrast virus particles in modified live vaccines replicate thereby inducing a more intense antigenic stimulus that triggers humoral and cellular responses. Revaccinations are required less often.

How long does immunisation last?

In general modified live vaccines induce a longer immune protection than inactivated vaccines. The protective effect of live vaccines might even last for a lifetime, whereas some vaccines protect for only a few months.