Viral interference was discovered about 60 years ago. Molecular epidemiology revealed that this phenomenon possesses important biological implications, it can reduce the epidemic spread of certain viruses from time to time (influenza and enteroviruses) and the efficiency of live vaccination can be impaired, too. Phenomena observed during the last 80 years in Hungary are analyzed. It is suggested to concentrate the distribution of MMR vaccines to seasons of limited influenza and enterovirus circulation. Interference seems to impair the progress of wild poliovirus eradication in the endemic tropical countries. It is recommended to enhance enterovirus surveillance in the region of European countries, since the exchange of the oral poliovirus vaccine to the enhanced inactivated polio vaccine might result in enhanced circulation of non-polio enteroviruses leading to the increase in the number of type I (juvenile) diabetes patients.