This could definitely be explained better but I’m short on time, so apologies if I’m unclear or confusing in my explanation
I was taught whilst studying vet nursing that for a vaccine to be effective you need to have had each component of the vaccination twice. Most puppies will be given a C3 initially, then a C5 then another C5, until they have had that last vaccination they are not covered for every component of the vaccination. There is also the issue of mother’s immunity and when it runs out. Some vets will argue that you should wait to 16 weeks for the last vaccination as in most dogs the mothers immunity will have run out therefore the last vaccination will be effective (as if you vaccinate when the mothers antibodies are still in the pup the reduces the effective of the puppy to create its own immune response to those diseases).
We did out last vaccination at 14weeks and took him walking 10 days later, I discussed this matter with my Vet and he did not feel that we had anything to worry about in regards to having him vaccinated at 14 rather then 16 weeks. However I was aware of the risks and decided to take that risk and we have not had any issues.
Vets all have differing opionions on vaccinations, there are also many different brands and types of vaccinations so I still feel the best thing you can do is discuss the matter with your vet and see what he/she has to say after all they are the ones trained in this field.
I highly recommend also enrolling your puppy in puppy class we found it to be such a wonderful way to socialise Marley, our last dog was not socialised properly and we paid for it… he was terrified of other dogs! Marley is now so confident and friendly with other dogs it was worth the money we paid. They also discussed everything from worming and vaccinations through to grooming.