The studies are published. They have to be made available to us.
Three-year duration of immunity in dogs following ... [Vet Ther. 2005] - PubMed result Evaluation of the efficacy and duration of immunit... [Vet Ther. 2004] - PubMed result
These pups weren't even given a dose at an old enough age to ensure protection.
The vets I know (several) who use the newer protocol aren't all young and they don't just change their ways without a good reason.
I almost lost my girl to a vaccine. That isn't to say we shouldn't vaccinate. I do and will continue to. But I won't do it as often as some vets are suggesting. Just in the last decade halothane is being used less and less. I'm really glad to see things like that. It has been replaced by something newer - and much better. So in that way, I'm very happy to see that vets will move ahead.
We do need to be careful about undervaccinating. And it's definitely not wrong to listen to our vets.. But I hope those vets are listening to the experts on this issue and every other issue.
Yes, there is a chance that a dog vaccinated every 3 years could get distemper and parvo. There is also a chance that a dog vaccinated annually could also.