Well, there has been a lot of studies and discussions about vaccination the last few years. They have done studies where they have seen that there is a higher risk for autoimmune dis. BUT I have consulted a lot of vets. both in this county and in sweden where I originally am from. The problem they mostly have seen in the studies are thyroids and it is in most breeds, it is still at a point where they can not for certain say if it is due to genetics in certain individuals or if it is a combination of the vaccine and genetics.
What several vets that I have spoke to regarding this, says that to cut short the puppy vaccinations is a way way bigger risk than the potential risks that could be from the vaccine. So always vaccinate the puppy shots, then the recommendation I have gotten is give the next years booster too, but always a one year booster. THEN after that, when you get to the second year of booster (not counting the puppy shots) it would be wise to do a titer and see what the immune system tell, you'll have to do two different titers to cover the info you need. The titers are approx 70 dollars each, but thats when they think it starts to get real important to check wether or not the dogs have enough antibodies or not. The risk seems to be when we keep giving boosters and they already have enough antibodies.
About heartworm meds. I have really not heard anything that makes me hesitate to give the monthly pill. If they do get heartwork that is a serious condition and a very riskfilled treatment.
I am not sure if it helped at all, I have several reports and articles I could send you if you would like to read more about it. pm me if you feel like some rather heavy reading
Marit