Can a Vaccinated Dog Get Parvovirus?

The reason you may be asking whether a dog with vaccinations can contract parvovirus is because of reports suggesting this may be the case^[1]. These reports were due to an increase in cases of parvo in American hospitals. Veterinarians report diagnoses of various diseases and send the information to the manufacturing laboratories or agencies responsible for creating the drugs.

There are various theories as to why this has occurred. Canine parvovirus is a viral disease which starts with symptoms of severe vomiting and bloody diarrhea. There is no cure, so treatment requires management of the symptoms. It has a high mortality rate.

Due to such high mortality, vaccinations against parvovirus are considered essential veterinary medicine. They are administered by giving an injection under the skin. Administration of these vaccinations is recommended for all dogs. Why then are more cases being reported and how are vaccinated dogs being affected?

One of the hypotheses being considered as to why vaccinated dogs are contracting parvovirus is the presence of a new strain of the disease. Viruses can change over time and mutate into different strains. Such a modification is likely to render the current vaccine ineffective.

However, it does not appear that this theory is correct. The virus has been changing since its discovery and different strains are already known to scientists. These differences are minimal and researchers have been aware of this current strain for years. In fact, the strain with which the spike in canine parvo virus cases have been registered is the one which has had the greatest presence of late.

While it is true that this specific strain is not included in the current vaccine, considering it is the most prevalent strain, many more dogs would be contracting the disease if it were ineffective. This shows that the current vaccine does offer protection against the current strain. However, the creation of vaccines is a perpetually evolving process. Current studies are investigating how small modifications in strains affect the efficacy of the vaccine.

The parvo vaccination is administered as a combination vaccine known as DHLPP. You can learn more about the other diseases they are protected against in our article about the DHLPP vaccination for dogs.

With the information currently available, one theory of why vaccinated dogs are contracting parvovirus is due to the interference of maternal antibodies. Female dogs transmit antibodies to their offspring via their first milk, known as colostrum. This is a rich form of milk which is designed to help give puppies the best start in life since they are at their most vulnerable. The antibodies passed on to the puppies stays with them for about 12 weeks of age. However, these antibodies are also known to interfere with the efficacy of vaccinations.

This problem a mother's milk affecting the efficacy of canine vaccines is one of the reasons we ask is vaccinating a pregnant dog safe? I general, it is best to not only wait until after the pregnancy, but also after the mother has weaned her puppies.

The goal of vaccinations is to stimulate the immune system. Stimulation results in the body being able to make antibodies against a particular pathogen in the future. This means a vaccinated dog should be ready to defend itself when it comes in contact with parvovirus. When an interference in these antibodies has occurred, their immune system may not be able to react effectively.

There are other factors which might affect the efficacy of the immune system. Some breeds are known to have propensity towards immunological deficiencies. This means individual dogs may be more likely to contract parvovirus, even if they have bee immunized.

One of the spikes in parvovirus cases has occurred during the recent COVID-19 pandemic. Another reason it is possible there are mor cases of parvovirus is a practical issue. Canine vaccinations do not work for the lifetime of the dog. They will need booster injections to retain immunity. Since people have not been able to take their dogs to veterinarians except in emergency cases, they may not have been able to take the dog for these repeat vaccinations.

One way to improve the effectiveness of the parvovirus vaccine is to simply adapt the dog's vaccination schedule. Typically, the first vaccinations given to puppies are completed around 12 weeks of age. As we have seen, it is possible that some puppies at that age still have maternal antibodies that will affect the effectiveness of the vaccine. Therefore, the current trend is to delay the first vaccination and give the last vaccine at 16 weeks. At this point, maternal antibodies are no longer present.

With the aim of improving the efficacy of vaccination, the possible interaction that occurs when the parvovirus and Leptospira vaccines are administered at the same time is being studied. It seems that when administered together, it may decrease efficacy against parvo. Amendments to vaccination schedules may be necessary for some dogs.

This effect will not have repercussions in all dogs, but in those in which vaccination does not stimulate high levels of antibodies. While further research is required, it may be important to take this information into account. The schedule being considered prioritizes administering essential vaccines against viral diseases and leaving those for Leptospira or Bordetella for 18-22 weeks of life.

You definitely do still need to vaccinate your dog against parvovirus. Despite the fact a vaccinated dog can contract parvovirus under the circumstances we have described above, all dogs would still be much more vulnerable without it. While the vaccination may not be 100% effective, it still provides needed protection against a potentially fatal disease.

Additionally, veterinarians have enough information to adjust puppy vaccination guidelines in order to improve the effectiveness of each vaccine. It is important, to achieve this, that we put ourselves in the hands of a trusted professional. Knowing how viruses spread and how to combat them not only helps our dog, but future generations of animals.

To know more about canine vaccinations in general, check out our video below:

This article is purely informative. AnimalWised does not have the authority to prescribe any veterinary treatment or create a diagnosis. We invite you to take your pet to the veterinarian if they are suffering from any condition or pain.

If you want to read similar articles to Can a Vaccinated Dog Get Parvovirus?, we recommend you visit our Viral diseases category.