One of the greatest frustrations occurs when a dog develops a disease against which it has been vaccinated. There are six primary reasons for this.
The vaccines made by government-licensed manufacturers are potent when they leave the factory, but several things may happen to inactivate them. The most common cause of vaccine inactivation is warming during shipping and handling. Temperature control is critical in maintaining potency. If the vaccine gets too warm during shipment to the distributor or storage at the distributor, it is inactivated. This is a common problem associated with vaccines purchased by mail order, the internet, or from feed stores. The buyer has no way to determine whether the vaccines were correctly handled during shipment to non-veterinary suppliers. Veterinarians routinely refuse to accept vaccine shipments if the vaccines are not stored with cold packs upon arrival.
"Veterinarians routinely refuse to accept vaccine shipments if the vaccines are not stored with cold packs upon arrival."
The opposite problem can occur if a vaccine is mishandled. The vaccine can become virulent (poisonous) or cause the infection it is intended to prevent.
Inherent characteristics of the vaccine
Although most of our vaccines have a very high success rate in dogs, none produces immunity in 100% vaccinated dogs. While vaccine programs are designed to maximize immunity, it is important to recognize that they do not provide 100% immunity against the disease.
The dog is not healthy when vaccinated.
The dog’s immune system must function properly to respond appropriately to a vaccine challenge. If the immune system is immature, it cannot do so. If the dog has a disease that suppresses the immune system or takes immuno-suppressive medication, it will not respond. If the dog has a fever, the immune system will be so "occupied" with the fever that it will respond poorly to the vaccine. It is important to discuss any health concerns with your veterinarian before vaccination.
Certain breeds of dogs appear to be especially susceptible to certain viruses. This has been observed for years, but recently it has been most evident in Rottweiler dogs and the canine parvovirus vaccine. Despite proper vaccination, a small but disproportionate number of Rottweiler puppies have reportedly developed parvovirus enteritis.
Interference due to maternal antibodies
When a puppy is born, she receives immunity-producing proteins, called maternal antibodies, from her mother. Maternal antibodies protect the newborn from the diseases her mother is protected against. Maternal antibodies last only a few weeks in the puppy; their duration is directly proportional to the mother dog’s immunity level. If her immunity level against rabies, for example, is very high, the maternal antibodies for rabies may last up to four months. If her level is low, they may persist for only five or six weeks. As long as these antibodies are present, the puppy is passively protected; however, those antibodies also block the ability to respond to a vaccine challenge. If a puppy receives a vaccination for rabies before the maternal rabies antibodies are gone, the vaccination is blocked, and no immunity develops. The same is true for the other components of the vaccines—the temporary immunity received from the mother can interfere with all the vaccinations.
"If a puppy receives a vaccination for rabies before the maternal rabies antibodies are gone, the vaccination is blocked, and no immunity develops."
Parvovirus seems to provide maternal immunity that lasts for quite a long time, up to four months in some dogs. For this reason, your veterinarian may recommend an additional parvovirus booster vaccination, given after the puppy series of vaccinations has been completed, usually at about 18 to 20 weeks of age.
Ideally, vaccinations should be given shortly after the maternal antibodies are gone but before the puppy is exposed to infectious organisms. There is no practical way to determine when the maternal antibodies are gone for each possible disease. Although theoretically, it is possible, it would be costly. Instead, the puppy is given a series of vaccinations at regular intervals, and protection is effective in most situations. However, if the maternal antibodies have waned after one vaccination and the puppy is exposed to the disease-causing virus or bacterium before the next vaccination occurs, the puppy will likely develop the disease.
The solution to this dilemma would be to give more vaccinations in the series. If it is known that the puppy’s environment is infected with a particular disease-causing agent, vaccinating every fourteen days from six weeks to sixteen weeks of age may be recommended. The disadvantage of such a plan is the expense. Instead of giving three vaccinations in the series, six or eight would be given. This would result in more than double the cost of the routine vaccine series. The potential benefits and risks of extra vaccinations can be discussed with your veterinarian.
Dogs and puppies can be exposed to large amounts of viruses or bacteria, especially in overcrowded or unsanitary conditions. In these circumstances, vaccine failures may occur.