Advocates of childhood immunisation consistently argue that there is no evidence to suggest that vaccines are dangerous. Claims that the MMR (measles, mumps, rubella) vaccine in particular causes autism has never been established. In fact, they say, every study has shown conclusvely there is no causal link.
Most of the studies 'proving' the safety of vaccines have tended to be small - often involving hundreds of children - and over quite short time frames.
So a group of parents in the USA have got together to do the job properly. Generation Rescue has been formed by parents whose children have been diagnosed with neurological disorders - and, as concerned parents, they want to know why.
But instead of just accepting the consoling words of doctors and scientists, they decided to do the job themselves. And they did it in style, raising enough money to fund a research study that has involved 17,000 vaccinated and unvaccinated children in the states of Oregon and California, making it one of the largest ever research projects into the health implications of childhood vaccines. They also tracked the health of the children right up to the age of 17.
They discovered that in the younger age group, which included the four-year-olds, vaccinated children were two-and-a-half times more likely to have a neurological disorder than children who were not vaccinated, while vaccinated boys were more than twice as likely to have ADHD (attention deficit, hyperactivity disorder), and 61 per cent more likely to have autism.
The differences became more marked in the older children, aged from 11 to 17. In this group, a vaccinated child was more than three times more likely to have ADHD than his non-vaccinated counterpart, and 112 per cent more likely to have autism.
The study suggests that the vaccine can have a longer-term effect than researchers thought, which might explain why they were unable to discover a connection within the days and weeks they were monitoring the children following vaccination.
So, why haven't we heard anything about this study, which is a significant addition to the debate? Well, it was carried out by parents, it wasn't published in a peer-reviewed journal, and it wasn't funded by a manufacturer of one of the vaccines, a combination that guarantees media obscurity.