Yes Tony there are dangers and much of it is found to be allergies, immune systems that cannot cope 100% with immunisation properties but I believe that to be able to address this problem lies in the proper understand of our personal DNA which will eventually give each individual access to prevention of disease.
In respect of declining rates in prevention has many answers, one of them being that people do not know that there are preventative measures that can be taken. Take in the UK for instance people fly off into exotic places WITHOUT protection or even the knowledge of it, so one cannot account for their ignorance or their attitude towards their health.