SadlyVaccination titres are unreliable, most vets only vaccinated when they have to. We do a full course for dogs then only some bits every 3 yeArs some every 2 and lepto every year- it only just lasts 12 months if that. Cats need yearly boosters as the flu bit doesn't last long and the Leucaemia bit is only 40-60% reliable! In 16 years of small animal practice I have never seen a major reaction to vaccines- sore necks and lumps but nothing life threatening. I have seen many dogs very I'll or die from ' natural' products such as herbal remedies, tea tree oil and garlic.
Nothing is 100% safe and unfortunately not everyone is above board, but conturary to popular belief, vets are not out to harm animals or make mega bucks off people! We spend time every year reviewing our drugs and vaccines to make sure we are using the safest products and not over using them, including antibiotics etc.
Sorry to rant had a rough week!