Why would a puppy vaccinated on the recommended schedule of 8, 12 , and 16 weeks get parvo? Were the vaccines bad? Is the puppy a mutant?
Probably not. The most common reason vaccinated puppies get parvo is because the system nature designed to protect them worked exactly as intended.
If a mother dog has sufficient immunity from diseases, she essentially vaccinates her puppies for those same diseases via colustrum (early milk) in the first 24 hours of life (Niewiesk, 2014). These maternal antibodies protect puppies from disease but they also block vaccinations.
A typical puppy vaccination schedule is 8, 12 and 16 weeks. This is not because the puppy needs all those vaccines. In fact, the puppy only needs ONE. However, since we do not know when the maternal antibodies will be low enough to allow the vaccine to work, we vaccinate across the weeks in which the maternal antibodies are thought to be waning.
This 8-12-16 week schedule, unfortunately, offers a false sense of security.
First, utilizing that schedule will likely create windows of susceptibility.
For example, imagine that the 12-week parvo vaccine was blocked by the maternal antibodies — this is totally reasonable and realistic, by the way. But the maternal antibodies continue to decline and are low enough at 14-weeks to leave a puppy unprotected against parvo. The next vaccine — the one that will work — is two weeks away, offering a nice bit of time for the puppy to get sick.
The second reason the 8/12/16 week schedule may offer a false sense of security is because a final parvo vaccination at 16-weeks may be too soon. Considering parvo vaccination and failure, Decaro, Buonavoglia, and Barrs (2020) note “…there is some evidence that some pups can still not be immunised at 16 weeks…” (p. 2).
FYI: Not a puppy.
So what do we do to keep our puppies safe — and minimize unnecessary and ineffective vaccinations? Here are a couple of related strategies that are effective and evidenced-based.
Determine expected levels of maternal antibodies.
A Canine Nomograph measures the expected level of maternal antibodies in puppies, providing guidance on effective use of vaccinations. It involves a blood test on a pregnant dog that is sent to a research lab at the University of Wisconsin-Madison, and results in an individualized schedule for vaccinations.
FYI: An individualized vaccination protocol is a safe and reasonable alternative to a one-size-fits-all vaccination schedule, and is supported by the American Animal Hospital Association (see, for example, https://www.aaha.org/aaha-guidelines/vaccination-canine-configuration/vaccination-canine/).
Use Titers.
A titer test tells us if a vaccination is protecting the dog from the disease; I have also used titer testing to determine when maternal antibodies are low enough in a puppy for a vaccine to work.
The same lab that does the Canine Nomograph offers titer testing and it is a screaming deal. Two of my puppy people were quoted a price for titers in the hundreds of dollars by their vets — the UW lab charges $44.
So back to our question: Why would a puppy vaccinated on the recommended schedule of 8, 12 , and 16 weeks get parvo?
Assuming the vaccine was not bad**, the most likely explanation is because 16-weeks was too soon for the final parvo vaccination in that puppy. Maternal antibodies were likely still in place, protecting the puppy from both the disease — and the vaccine.
The solution is simple: Whatever puppy vaccination schedule you decide to use, always run a titer test at least two weeks (three is better) after the last vaccination to make sure the puppy is protected.
Easy Peasy.
Work Cited
Decaro, N, Buonavoglia, C, & Barrs, V.R. (2020). Canine parvovirus vaccination and immunisation failures: Are we far from disease eradication? Veterinary Microbiology, 247, 108760.
Niewiesk, S. (2014). Maternal Antibodies: Clinical Significance, Mechanism of Interference with Immune Responses, and Possible Vaccination Strategies. Frontiers in Immunology, 5, 446.
**Let your veterinarian do vaccinations, please. This maximizes the chances of optimal handling of those vaccines, and it helps build your relationship with your veterinarian.