Dog - Vaccination Failures

Vaccinations both for us and our animals are constantly improving but occasionally failures still occur.

Why is this?  

There are five main reasons:

1.  Ineffective vaccine.  In the UK vaccines have to be licensed by DEFRA following stringent testing before they can be marketed.  They are potent at the time they leave the factory but several things may happen to inactivate them.  A common cause of deactivation is that they have been subjected to too high a temperature prior to use.  Veterinary suppliers are careful to ensure that vaccines are always distributed at the correct temperature.  Similarly potency can be severely affected if there is undue delay between preparation of the vaccine and its administration.

2.   Inherent characteristics of the vaccine.  Most of our vaccines have a very high success rate but none can be expected to confer complete protection in every dog vaccinated.

3.  The dog is not healthy.  It is mandatory for the canine immune system to function properly in order to respond to the vaccine challenge.  If the immune system is immature or the patient has an underlying problem that is suppressing its immune system, the required response will not occur. If the dog is pyrexic (has a fever) at the time of vaccination, the immune system will be so 'occupied' with fighting the cause of that fever that it may respond only very poorly to the vaccine challenge.

4.  Breed variation.  Certain breeds of dogs have been found to be particularly susceptible to certain viruses.  For example Rottweilers appear particularly susceptible to canine parvovirus (CPV).  A disproportionate number of Rottweilers that have been properly vaccinated have developed parvovirus infection.

5.   Interference due to maternal antibodies.  At birth a puppy receives maternal antibodies in the milk which will protect it from diseases against which the mother has immunity.  These maternal antibodies only last a few weeks in the puppy; their duration being directly proportional to the level of the dam's immunity (i.e the higher the mothers level of immunity, the longer the protection she passes to the puppies).  If her immunity level against parvovirus, for example, is very high, the parvovirus antibodies which the puppy receives may last up to 4 months whereas if her antibody level is low, protection in the puppy may persist for only 4 or 5 weeks.  Maternal antibodies in the puppy at the time of vaccination can interfere with the build up of the puppy's own immunity, not only to parvovirus but to the other diseases currently inoculated against with combined (multivalent) vaccines (e.g. distemper, parainfluenza, kidney disease, etc.).

With the development of modern vaccines, it is possible to protect puppies even in the face of circulating maternal antibodies but it is important that the manufacturers' recommendations are strictly followed regarding repeat vaccinations and the interval between them.  It is for this reason that should the interval between boosters be too long, the vaccination programme has to be re-started.  In order to avoid possible vaccination failures the course of vaccination for each puppy has to be considered on an individual basis taking into account the amount of infection in the area as well as the breed and type of pup, immune status of the dam etc.  In general terms, with modern vaccines this involves a course of vaccines starting sometimes as early as 4 weeks of age with a final booster at approximately 16-20 weeks.  In order to ensure as high a level of protection as possible it is essential that all dogs receive a multivalent booster covering all the diseases protected against one year after completion of the initial vaccination course.  Then the so-called core vaccines such as distemper, parvovirus etc., may only need booster vaccinations every two or even three years, according to the manufacturers' recommendations.  In areas of high risk vaccination (against kennel cough for example) maybe required even more frequently than every twelve months.

Please contact us if you would like to discuss this further.