Get the most out of it: How to use vaccines effectively

Only healthy pigs deliver their full genetic potential. Vaccines against endemic diseases are an important cornerstone for keeping pigs productive. It is a smart approach to make use of the body´s own defence mechanisms by using vaccines that switch on the pig’s immune system. You prepare the pig for the “real” attack of the infectious agent, which leads to a lower impact on production.

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However, a vaccine will not boost your production in all cases. There are a few key facts that are needed for success. A vaccine is specific for a pathogen and must be delivered correctly. Vaccinations must happen in enough time ahead of an infection to allow the body to build immunity. And pigs must be able to respond.

So, how can we get most out of the vaccination programme?

Choice of vaccine

A vaccine is always specific to an organism, that is, it contains material from a specific pathogen called antigen. The antigen in the vaccine determines to the immune system who the “enemy” is. And it needs the complete formulation of the vaccine to trigger an effective immune reaction.

If health problems occur, it is necessary to conduct a meaningful diagnostic work-up to find the cause of disease. Various pathogens and non-infectious factors can cause similar symptoms (see case 1). Starting with a definite diagnosis, vaccination can effectively protect the herd.

Storing and administration

It is of paramount importance to consider the manufacturer’s instructions for storage and use. Incorrect storage – too warm or too cold – can lead to destruction of the antigen and turn the vaccine ineffective. Wrong storage also has the potential risk to increase adverse reactions in the pigs, such as system or injection site reactions. Studies in pig farms revealed that up to one-third of refrigerators used for the storage of vaccines are too warm or too cold. Before use, some vaccines must be allowed to reach room temperature.

Vaccines are for immediate use after opening with very limited time span to keep open vials in use. Light, oxygen and potential contamination lead to ineffectiveness or even cause damage when used (see case 2). However, studies showed, that roughly one- to two-thirds of all interviewed farms, put opened vaccine vials back in fridge for later use.

The vaccine needs to be administered at full dosage in the correct location. According to a study, up to 80% of injections in practice are not placed correctly or under-dosed, in worst cases. This number provides an enormous potential for improvement.

Being self-critical and checking back on storing and administration can get more out of the vaccines you are using.

Timing of application

Vaccination needs to happen well ahead of the expected time of infection, as immunity must build. It takes about 2 to 3 weeks to build or boost immunity after vaccination depending on the product and type of vaccine. For a 2-dose programme this means 2 to 3 weeks after the second shot. The effect of vaccination is long-lasting and continues protecting pigs when they are challenged during the duration of immunity.

Vaccination must happen early enough to protect against natural challenge, but it should not be conducted too soon. On the one hand, maternally derived immunity – mainly maternal antibodies – are transmitted via colostrum and can impair the efficacy of some vaccines given to piglets. On the other hand, although all parts of the piglets’ immune system are developed at birth, it matures over time and will increase its response over weeks. The relationship is linear: The younger the animal, the lower the immune response. The older the animal, the better the immune response.

The status of the animal or its immune system

In case of vaccination, the immune system is the crucial element of success. Several factors can negatively affect an immune response. To name a few: stress, mycotoxins, malnutrition, or a concurrent infection with another organism. A good example in relation to the last point is the porcine reproductive and respiratory syndrome virus (PRRSV). It has been demonstrated that PRRSV infection at the time of vaccination against M. hyopneumoniae (M. hyo; Causing enzootic pneumonia) can reduce the effectiveness of the vaccine. Nutritional state and feed supply must be considered. It requires energy to “train” the immune system and proteins, specific trace elements and vitamins are essential for a solid immune response.

Yet, a vaccine cannot compensate for weak management. Even a well-trained immune system may fail to protect in the face of an overwhelming pathogen challenge due to weak biosecurity, bad ventilation and pig flow management.

Conclusion

Checking vaccination programmes for what, how, when and who is worth a lot, to get most out of the vaccines in use.

Case 1: Wasting pigs in the nursery

Approximately two weeks after weaning, many piglets showed wasting and the group was unevenly thriving. In addition, piglets occasionally had few specific symptoms such as diarrhoea and conjunctivitis. Cough was barely noticeable. The piglets looked like suffering from the systemic disease caused by PCV-2 (PCV2-SD), formerly named postweaning multisystemic wasting syndrome. But those pigs had been vaccinated against porcine circovirus type 2 (PCV-2). A diagnostic investigation was carried out which found PCV-2 in the affected pigs.

Was PCV 2 causing the disease? -> No!
Vaccination does not protect against infection, but against clinical disease. So, the pathogen can also be detected in successfully vaccinated pigs. If PCV-2 causes disease, corresponding changes are also found in tissues. In the present case, however, no tissue lesions could be detected in several piglets examined.

What was the cause?
In the initial investigation, diagnostics were solely aiming to find PCV-2, not checking for other differential diagnosis. In the present case, a more thorough investigation, found PRRSV as cause of the clinical disease.

Case 2: Contaminated vaccine

A producer reported health issues in piglets shortly after weaning until several weeks later. Some of the piglets showed vomiting and a reduced general condition immediately after vaccination against PCV-2 and M. hyo. Later pigs showed wasting. First investigation identified PCV-2-related tissue lesions, thus, PCV-2 as the suspected cause of disease. Piglets were vaccinated against PCV-2.

Did the vaccine fail to work? -> No!
On the one hand, tissue lesions were also found in piglets that had been vaccinated only 1-2 days before and the extent of the lesions suggested that disease must have started earlier. In any case, vaccination would have been too late to protect those pigs.

On the other hand, further investigations showed that the vaccine gun and some of the used vaccine vials were heavily contaminated by bacteria and fungi. In this case, the vaccine was stored openly for several days, attached to the vaccine gun, which was not properly cleaned after use. It can be assumed that the contamination has turned the vaccine ineffective. And beyond that, the injection of the contaminated fluid caused some of the health problems of those piglets.

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24-06 | Article