TINY Sam Muschamp was the picture of health when his doting father allowed a promotional photograph to be taken as he was given a vaccine for mumps, measles and rubella (MMR).

His distraught father, David, is now convinced that the vaccination was a terrible mistake, and, as a direct result his son developed autism. He is now a bitter opponent of the MMR jab. But Bolton's public health officer, Dr Robert Aston -- a leading expert on immunisation -- is one of the UK's strongest advocates of the vaccination.

He too has suffered a personal tragedy that could have shaken his faith in the safety of the jab. It did not. Health reporter Gayle Evans speaks to both men