Vaccination Failures in Dogs

Why would a vaccine fail?

Vaccines are designed to protect against disease, so it is frustrating when that doesn’t happen and a dog develops a disease against which it has been vaccinated. Vaccine failures are rare, but they can occur. There are six primary reasons why a vaccine may not work.

1. Ineffective vaccine

Vaccines made by government-licensed manufacturers are potent (active) when they leave the factory but may lose their potency on their way to the veterinarian. Most commonly, warming during shipping and handling can inactivate a vaccine. 

Temperature control is critical in maintaining potency. This problem is often associated with vaccines purchased directly by pet owners via mail order, internet, or feed stores, because the buyer does not know whether the vaccines were correctly handled during shipment. Veterinarians do not accept vaccine shipments unless the vaccines are stored with cold packs.

2. Inherent characteristics of the vaccine

Most vaccines have a very high success rate in dogs, but none produce immunity in 100% of vaccinated dogs. Vaccine programs are designed to maximize immunity, but it is important to recognize that no vaccine provides 100% immunity.

3. The dog is not healthy when vaccinated

The dog’s immune system must function properly to respond appropriately to a vaccine. If the immune system is immature or is suppressed by disease or medication, it will not respond. If the dog has a fever, the immune system may respond poorly to the vaccine because it is already responding to the fever. It is important to discuss any health concerns with your veterinarian before your dog is vaccinated.

4. Breed predisposition

Certain dog breeds appear particularly susceptible to certain viruses. Most recently, this susceptibility has been evident in Rottweilers with the canine parvovirus vaccine. Despite proper vaccination, a small but disproportionate number of Rottweiler puppies have reportedly developed parvovirus enteritis.

5. Interference of maternal antibodies

When puppies are born, they receive immunity-producing proteins, called maternal antibodies, from their mother. Maternal antibodies protect the newborn from diseases the mother is protected against. How long maternal antibodies stay protective in the puppy can vary widely from five or six weeks to four months. Maternal antibodies protect a puppy against infection, but that also includes blocking the effects of a vaccine. This prevents a vaccinated puppy from building their own protection against the disease until the maternal antibody number decreases.

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 exactly when maternal antibodies disappear for each possible disease. 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.

If a puppy is considered to be at higher risk for exposure to a pathogen, such as during an outbreak situation, your veterinarian may recommend vaccinating more frequently. You can discuss the potential benefits and risks of extra vaccinations with your veterinarian.

Maternal immunity for parvovirus seems to last a long time, up to four months in some dogs. For this reason, your veterinarian may recommend an additional parvovirus booster vaccination after the initial series of vaccinations is complete, usually at about 18 to 20 weeks of age.

6. Overwhelming exposure

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.