Hi Gary. If your vets are happy to titre test, then it’s quite reasonable to follow their advice. However, it’s also likely that the vaccine will not provoke a reaction this year. We often find that it varies as vaccines are never the same from batch to batch. Additionally, most of the time an antihistamine, given 10 minutes prior is helpful.

Hi Robin – The issue here is probably both of the variation in vaccine label claims and the preferences of each vet. However, there is also likely to be a price difference based on the bulk price that a vet gives a breeder versus the price for an individual vaccination (which includes a consultation fee).
In your case, a few thoughts come to mind. If the C5 did not include an intranasal kennel cough vaccine, then in fact it needs to be a C5 that is repeated, not a C4 unless you want incomplete vaccination. Of course, kennel cough is not the most essential part of the vaccine, but it is still important.
Secondly, Protech vaccines have a label claim of protection against parvovirus from 10 weeks of age. Therefore, although I certainly recommend a 16 week shot as well, you are welcome to decline a third vaccination based on the label claim. That means if there is a vaccine failure and the vaccine was given under correct circumstances, it is probably the vaccine manufacturer who is liable.
C4 vaccines are rarely used these days as we are either going for full C5 or C3 (in fact our 16 week vaccination is a parvovirus-only vaccine, essentially a C1!)
Lastly, there is probably no great difference in performance between Nobivac and Protech vaccines, although personally I use Nobivac.
I’m sorry if this just makes it all seem more confusing!If it helps, I’ve compared the age for vaccination with different brands here.