Monday , 25 September 2017

To Vaccinate or Not to Vaccinate…

By: Dr. Amanda Glew

To vaccinate or not to vaccinate, that is the question.

When I first graduated (and that was a few years ago), we vaccinated with everything, every year. However, similar to human medicine, it became more and more apparent that yearly vaccines are not required (we went from tetanus shots once per 5 years, to once per 10 years in humans). A huge debate ensued about the interval in between vaccinations, and which vaccines are required and when.  One of the big questions is duration of immunity (DOI) which really can only be answered by challenge studies. One of the problems  in doing these studies is the control group has to be the same as the challenge group- which for a DOI study of rabies vaccines, well you can imagine, keeping a group of control animals for 3 years then submitting to a supposedly 100% lethal dose of rabies is rather difficult even for researchers.

Add to this the now known event of “acquired immunity” – that with age animals immune system may develop an immunity to a potentially fatal virus (which makes sense for survival means) – then challenge studies are even more difficult to accomplish.

So what do we know? Well, we know that we are lucky to have excellent vaccines that provide almost 100% protection when the animal is exposed to these fatal diseases. These include distemper/parvo/rabies in dogs and panleukopenia in cats. These are what we call “core vaccines” and all of our pets should get at least one of these vaccines past the age of 14 weeks.  So why do we start at 8 weeks of age? Because the maternal immunity blocks the development of immunity, and we don’t know when a puppy/kitten will get their own immunity. By 14 weeks, it is pretty sure they will. However, if it drops earlier (9-10-11 weeks), then they are potentially exposed. Hence the  reasoning for a booster every 3-4 weeks booster until 14 weeks of age. These vaccines will provide an immunity within 48-72 hours, but we recommend a minimum of 1-2 weeks before exposing the young animal to a risk situation (dog parks, other dogs, groomers, surgery at the vets). Does an animal over 14 weeks of age need a booster 3-4 weeks later? Probably not, but it is recommended anyway.

There are some animals who never “seroconvert” (develop an immunity). This is one of the reasons for apparent vaccine failure- Rottweillers were one of these breeds who had this issue. But natural selection weaned these out of the breeding line pretty quickly, so this happens much less now. How do we know who converts? Only by doing titer tests- which up to now, were only available at quite some cost at laboratories.

I have forever been predicting that a company should have a “bed-side” test to quickly evaluate titers levels of animals- and sure enough, Aventix has come up with one. This means that we can now offer clients who are concerned about “over vaccinating” a titer level to see 1. If the puppy has seroconverted and 2. After a few years, does he or she require a booster or not. Currently this is only for the core vaccines, and only for dogs- but it is a start.

A summary of what I would recommend is as follows for core vaccines:

8-12-16 weeks DAPP dogs, rabies (R) 4-6 months – follow up with a titer test to ensure seroconversion, then a year later, either a booster DAPP-R or another titer test. Then rabies every 3 years, and titers every 1-2 years. If your animal has an allergic reaction to the vaccines, then he likely has a lifelong immunity, so why risk another vaccine? Titers again

8-12-16 weeks FVRCP cats, R 4-6 months. Booster one year later FVRCP-R. Then every 3 years FVRCP, every 3 years if using an appropriate 3 year rabies vaccine, but if concerned about sarcomas, then purevax vaccine is currently licensed for 1 year only (this is another discussion in itself). Titers can be done, but not in –house at this time.

The main thing is to have the last core vaccine after 14 weeks of age, unless you do a titer level.

Next blog, I will discuss “non-core” vaccines, and current thought on these.

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