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Figure Out Why Vaccines Fail – for Sep. 6, 2010

I have always said farmers put a lot of effort, along with their veterinarians, into selecting their annual vaccination protocol. They should. Vaccines cost money and effort is required to administer them. We must maximize the immune response to get maximum protection of our livestock. This is good from both a biosecurity standpoint as well as an economic one. Clinical disease such as scours, pneumonia outbreaks or abortions all affect our bottom line.

Despite all that effort, vaccines do sometimes fail. This article will attempt to outline why this happens and what you can do to prevent it. Often it only takes a small effort, a bit of planning, and adhering to a few principles to be sure you get the maximum benefit from your vaccination program.

The first place to check is your application technique. Gone are the days when farmers only administer blackleg. It was a fairly tough vaccine with a high level of efficacy and immunity. In short, it was hard to muck it up unless the vaccine had expired or was exposed to the elements.

Nowadays with multiple vaccines, some of them pretty fragile and given in all kinds of weather, extra care must be taken.

With multiple shots now being given it probably is best to first establish which diseases you are most concerned about and then select the products that give you the best response with the fewest number of shots. Multiple shots do increase the chances of making a mistake.

When giving multiple vaccines I adhere to several principles that minimize the chances of a blunder.

First off, keep a cooler or Styrofoam box around to avoid overheating of the product in summer and, even more important, freezing in winter. You can place ice packs in the cooler in summer and warm water bottles in winter.

You know the saying about the weather changing quickly, so be prepared. Warm sunny days can turn into blustery winter ones in a heartbeat. Those are the times when an insulated container can save the day. Depending on how hot or cold it is even the syringe loaded with vaccine needs to be protected. Ideally we want the outside temperature to be in the 5-15 range before administration. Keep in mind it is going into an animal with a 38-39 (approx. 100 F) temperature so warmer is better then cooler. If any freezing or crystallization occurs the vaccine is lost and must be disposed of.

It is no use giving inactivated, substandard vaccine when so much depends on it working properly.

Storing it in an insulated container also keeps the vaccine out of the sunlight, which is a good thing.

If more than one person is vaccinating split the shots over both sides of the neck. Inject subcutaneously wherever possible. It is absolutely imperative that the automatic guns don’t get mixed up halfway through processing. With the majority of vaccines now at two cc, dosage guns are often refilled at the same time and mix-ups can occur.

For example, if you were giving a blackleg vaccine (they often have formalin in the bacterin) and then refilled it with a four-way modified live vaccine even the very small amount of blackleg vaccine left in the syringe would inactivate the viral vaccine. The next full syringe of 25 doses would be useless. To avoid this I closely note the colour of the vaccine and often write the vaccine’s name on the syringe. I keep the refill bottles together with the vaccine gun and if two or more shots are given on the same side I carefully separate the guns on the table so it is harder for me to mix them up.

Likewise, the injection sites need to be separated as well. I recommend at least 10 cm between injection sites, the further the better.

Should you every need to do a follow up on a vaccine reaction, it’s a lot easier to keep track if you always give one vaccine high on the neck the other low. The secondary site is behind the shoulder or elbow.

Be cognisant of those times when there is lots of back-flow of the vaccine, or you go in and out and squirt vaccine into the air. If in doubt revaccinate these animals right away.

Monitor the usage to make sure the gun is dispensing the right amount and make sure the air is out of the syringe. And, always change bent, burred, dull or dirty needles.

Vaccine reactions (lumps or swellings) are normal. What we want to avoid are infected sites or putting the vaccine intradermal (between the skin layers) or intramuscular if it is supposed to be subcutaneous.

A number of vaccines can be given either subcutaneously or intramuscularly, so if an attempted subcutaneous shot ends up intramuscular it’s still okay.

Clean the syringes with warm water, no soap or disinfectant unless they are going to be thoroughly washed and dried.

When using modified live vaccine don’t mix up more than you can use in the next hour, and discard any unused product at the end of the day.

If killed vaccines and bacterins are drawn out in a sterile fashion, they can be held over for one week.

You should be aware of how the vaccine has been stored before you purchase it and are on the way home. We send purchases home with ice packs in summer and only use pharmaceutical suppliers we can trust. One fault in this supply chain can render the vaccine inactive. Many producers bring in a cooler when purchasing large quantities of vaccine so the temperature is maintained.

When handling cattle try to be diligent and vaccinate every animal. When you have escapees try your best to rerun them as they have not been treated.

To develop an immune response cattle must be healthy, in good nutrition and as free of stress as possible when they are vaccinated. The vaccine is only as protective as the response the animal can muster. Poor health and stress are two common reasons why vaccinations fail.

Always check expiry dates. I had one producer tell me he thought vaccines lose about 10 per cent of their efficacy for every year past expiry. No wonder he had a blackleg outbreak using vaccine that had expired nine years previously.

With so many different combination products out there make sure the diseases you want to protect against are in the vaccines. Producers sometimes think everything is in an eight-way vaccine — it isn’t.

Vaccinate according to label instructions, have the cattle healthy and you can expect maximum protection. I believe vaccines are the most integral part of any biosecurity program. If you hold back on vaccinating for diseases in your area eventually there will be consequences. Your veterinarian can give you a list of the diseases you should be worried about.

About the author


Roy Lewis is an Alberta-based veterinarian specializing in large-animal practice. He is also a part-time technical services vet for Merck Animal Health.



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