Why vaccines sometimes do not work

We have probably all had a situation where we have vaccinated against a particular disease but have still had the odd bird getting the disease against which we vaccinated.

Why does this happen?

If the odd bird gets the disease after vaccination..........

Was that bird in the loft at the time of vaccination?

Was the vaccine administered correctly?

It can happen that:

The vaccine was injected onto the skin instead of into the skin.

The needle was pushed right through both layers of the neck skin. The vaccine is then deposited on the other side of the pigeon's neck.

Automatic syringes with leaking seals will suck in air. This will result in air being injected under the skin instead of vaccine.

If many birds still get the disease after vaccination....

Has the vaccine expired?

Was the vaccine allowed to become hot during transport from Manufacturer to Wholesaler or from Wholesaler to Retailer or from Retailer to Fancier to loft?

Live vaccines that have to be mixed must be used in the shortest possible time. This applies with some of the Pox vaccines. Was the vaccine used long after mixing? With any vaccine, if the vaccination process is going to take a long time the vaccine that is still to be used should be kept in a cool box. With a vaccine that needs to be mixed (a live vaccine) keeping the vaccine cool is not really going to prolong its useful life. You still need to use it in the shortest possible time.

When a new strain of virus emerges the existing vaccine does not offer full protection. This has happened to us many times with Pox. New Pox vaccine needs to be developed every decade or so.

During an outbreak of Paramyxo, for example we vaccinate the birds as soon as possible but despite this vaccination we still get cases of Paramyxo. We see this as a vaccination failure but what has in fact happened is that the natural disease is developing quicker than the immunity provided by the vaccine. Oil based vaccines can take up to nine weeks to provide the pigeon with a COMPLETE immunity. When vaccinating against Paramyxo during an outbreak we have to accept to odd case of Paramyxo until a full immunity develops. For this reason it is important to vaccinate youngsters as soon as possible after weaning and not wait until the disease appears.

If the birds are not 100% healthy when they are vaccinated it can happen that they do not develop a full immunity. This is particularly true when a bird has an underlying Circovirus infection. While they have this infection they are incapable of producing immunity to the disease being vaccinated against.

After all the above criteria have been met it can still happen that the odd vaccinated bird still gets the disease. It is unfortunately a known fact that no vaccine is 100% effective. A very small percentage of birds can still show what is called vaccine breakthroughs.

by DR. R.C CONRAD

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