Bill Durodié is right to say there is little scientific evidence to indicate that the MMR vaccine causes autism (Letters, THES , January 2).
But most parents are not scientists with specialist knowledge, and when they make their decision they consider the possibility that their child will be harmed. They use a variety of sources for assessing such risks. It is hardly surprising that some parents are cautious and unwilling to accept reassurances that the MMR vaccine is safe. Most parents are familiar with the ways new technologies and new diseases create hazards and that, in the early stages at least, there is no scientific evidence for such "virtual risks". The failures associated with BSE and vCJD are now well documented.
Andy Alaszewski Centre for Health Services Studies University of Kent