This has come up quite a bit on the forum lately, so I have put an article on this topic, on the main site today. It's called Labrador health: medicines and their side effects.
Re: Side effects of medicines, wormers, vaccinations etc That is very useful Pippa, thanks. An emotive subject not just for animals. I think the point about herd immunity is really important, and was illustrated in the human population not so long ago with the measles outbreak (resulting sadly in UK deaths). I have heard a lot about "over-immunisation" in veterinary practice, and that may well be the case, but better this than under-immunisation which puts not only your own dog at risk, but also others. I personally, would rather not take the risk for major disease such as those covered by the conventional vaccinations, but might be more inclined to weigh up the pros and cons of flea and tick treatments and wormers, or at least their frequency of use, basing it on prevalence factors and local veterinary advice. Expert local knowledge goes a long way in keeping us and our furry friends protected.