Extended Duration Vaccine Protocols

Dr. John Ellis is a professor of Veterinary Microbiology at the University of Saskatchewan's Western College of Veterinary Medicine and a well-known expert on vaccine safety and efficacy. In the following interview, Dr. Ellis gives his thoughts about the debate surrounding new vaccine protocols.

DVMvac.org Fort Dodge Animal Health announced in March the USDA's approval of Duramune® Adult. What does this product mean for the vaccine debate?

Dr. Ellis I think that remains to be seen, because I believe that it will only be after veterinarians change their recommendations en masse that we will be able to actually draw conclusions from use of any particular vaccine or protocol.

DVMvac.org While there are no specific numbers, industry observers are reporting a growing trend of veterinarians who are using modified vaccination schedules. Do you believe that this is true? How do you view the professional approach to new vaccine guidelines?

Dr. Ellis I believe that the vast majority of veterinarians have not changed their recommendations with regard to annual vaccination. And again, I don't think we'll be able to draw any conclusions about the new protocol until virtually everyone starts using it. It's under those conditions that all the other factors related to population biology come into play.

DVMvac.org Any idea how long that will take?

Dr. Ellis I would predict it's going to be quite a while. I don't think most people are going to change. Certainly, the current market research that I've seen indicates that about 70-80% of the veterinarians haven't altered their recommendation for annual vaccination.

DVMvac.org Nonetheless, do you believe more practitioners are now questioning the need for annual vaccinations?

Dr. Ellis I think that that's a correct observation.

DVMvac.org And that's based primarily on concerns about the safety of annual vaccinations?

Dr. Ellis Well, I think it's ironic that one of the reasons that people are concerned is that vaccination has worked so well so that there's a very low prevalence of many infectious diseases in animal populations. So people can tend to focus on adverse events.

DVMvac.org What do you think about attempts by vaccine manufacturers to adapt to changing protocols, both feline and canine?

Dr. Ellis Frankly, I think that a large part of the debate regarding how frequently to vaccinate has been based on the ignorance, for lack of a better word, of young graduates with regard to infectious disease. They simply don't have experience with infectious disease because they haven't seen them. They've been fortunate to grow up in a time when most pets have been vaccinated pretty regularly. So I think the driver in a lot of this is a lack of experience with infectious disease, along with expert opinion that's been based on not very much data.

DVMvac.org What does the USDA approval of Duramune® Adult give veterinarians that they didn't have before?

Dr. Ellis I think what the challenge data will provide for some people is a degree of security about protocol change. It's another piece in a very complex puzzle.

DVMvac.org Will veterinarians view the development of Duramune® Adult as an effort by Fort Dodge Animal Health to support them in the use of vaccines?

Dr. Ellis Yes, they've changed the vaccine to improve it, I believe, and they do have some challenge data to support the idea that the vaccine will provide longer duration of immunity.

DVMvac.org Eventually data will emerge from the use of these vaccines, and over time this information will presumably support the contention that there is extended immunity, or not.

Dr. Ellis That's correct, but we won't really be able to assess the success of the change until everyone adopts the protocol. Otherwise, you still have the majority of the people using the old protocol, and as a result, you don't have enough of the population that's been vaccinated every three years to really assess it.

DVMvac.org Can't you isolate those that have vaccinated every three years to determine efficacy?

Dr. Ellis Not really. That makes sense at first glance, but probably the most important factor in the way that vaccines work is by affecting herd immunity, and if most of your population is vaccinated every year or about every year, you really can't draw any conclusions about those that aren't even vaccinated at all, because if you have the majority of the population vaccinated at a different interval, then they're providing some level of herd immunity in the overall population.

DVMvac.org Do you think at some point extended vaccine intervals will be common?

Dr. Ellis That may be. It's difficult to say. I think as the population of veterinarians change and the older veterinarians retire in the next, maybe five or ten years, then more people may go to three-year protocol. But after that, it may take five, 10 or even 20 years to actually see the effect. So it's a long-term proposition.

DVMvac.org Bottom line, where do you come down on this? Do you think it makes sense to begin that migration, at least in a preliminary way with a product like this? Or are you not at all convinced the data is there and therefore would prefer to stay with annual vaccination for the foreseeable future?

Dr. Ellis Well, from a scientific standpoint, I'm all for testing a new protocol. But again, the only way that's going to really provide any relevant information is if everyone does it. So from a scientific perspective, yes, I'm all for changing protocols to see if they work at a population level. But on the other hand, I'm also against it because the recommendation for annual vaccination has served us so well without much in the way of adverse reactions.

DVMvac.org With vaccines that offer extended duration of immunity, many pet owners may think annual vaccinations are simply no longer necessary. How can veterinarians clearly and effectively communicate to pet owners that many diseases, such as lepto, Lyme and others, still require annual vaccination?

Dr. Ellis That's a very difficult proposition because what it gets to is the complexity of infectious disease. It's going to become a challenge for the average practitioner to educate their clients about infections and disease, and how they relate to the lifestyle of the pet, and based on that make a good decision about how frequently to vaccinate. Veterinarians will have an even greater responsibility to play a more nuanced role than in the past with respect to protocols.