If vets are directly advising against the guidelines provided by the vaccine manufacturer, that is slightly concerning. It can definitely cause problems with insurance - I've seen that happen, refusing to pay out on a respiratory condition because vaccines had lapsed - no proof that the condition was to do with flu, in fact almost certain it wasn't, but flu vacc had lapsed so no cover. I have also seen animals where vaccines have lapsed have confirmed diagnoses of lepto, cat flu and feline leukaemia virus too. Titre testing has it's limitations, and costs a lot more than the vaccines themselves, as well as requiring a blood sample which can be more stressful on the animal than a quick injection - it's not unusual to need to sedate cats for a blood sample. So for me it comes down to - what reasons are there to not follow the vaccine manufacturers' guidelines? Either money - well, the alternatives have the potential to be a lot more costly. And actually at my practice, for existing clients, we don't charge extra for restarting the course, we charge an 'amnesty' rate which is the same as a single annual booster (and a lot of client's objections to a restart vanish when they realise it doesn't cost them any more). A fear of side effects? Side effects are vanishingly rare, clearly we would not be using something regularly for our own animals if we believed there was a significant risk of doing them harm. So unless someone has a philosophical objection or suspicion of vaccination in general, surely the rational decision is to stick to the guidelines we have, until we come up with updated ones when or if further evidence is beyond doubt.
FWIW, if a client asks me this question, I will have this very conversation, openly and without judgement. I have clients who choose not to vaccinate and I respect that and don't pester them about it, simply confirm their position when I see them etc. I still recommend an annual physical as a minimum, without which we can't prescribe POM parasite control
etc, and I vaccinate my own pets according to up to date manufacturers guidelines.
Btw one misconception on this thread - our quarantine regulations are nowhere near as strict as Australia. If they were then we might have avoided introducing babesiosis from the continent. A lot of us also consider it somewhat inevitable that an animal carrying rabies will get through sooner or later, it will probably be a fancy pedigree puppy imported underage with fudged paperwork from central/eastern Europe and sold on gumtree. That's a whole other thread though!