Most recently Dr Farrington, a lecturer in the Open University's Department of Statistics, has helped prove there is no link between the controversial measles, mumps and rubella vaccine (MMR) and autism or Crohn's Disease.
A behind-the-scenes number-cruncher who proves the theories and makes sense of the facts and figures, he is the expert who took all the medical data and calculated that in the hundreds of cases examined there was no link between the vaccine and the diseases.
Dr Farrington's interest in infectious diseases was fired while working at the Public Health Laboratory Service in London, and since then he has analysed the incidence and prevalence of such conditions as diphtheria, tetanus, hepatitis, CJD and HIV.
He believes strongly that statistics are a way of solving practical problems at a time when the public is often overwhelmed by conflicting messages.
"I don't think it's good for the medical establishment to tell people what to do all the time without any explanation. There has been a growth in the number of pressure groups both for and against vaccines and I welcome that," he says.
"It's my view that all establishments should be kept on their toes. It is terribly difficult for people who have to make a choice to know which expert to believe.
"This is the biggest study and not only did we find no evidence of a link - but the evidence is also very strong."
Dr Farrington used his own new method of statistical analysis when examining the MMR data. The study was launched following a report two years ago which suggested there was a link between the vaccine and autism. That study was based on 12 cases of autism - the new study looked at 498, the largest research programme undertaken to date.
Dr Farrington says the findings of his analysis are unequivocal: "The statistical evidence is quite clear and quite strong. While you can never prove there is not a link all you can ever say is that we have looked very hard and we haven't found a link."
After the initial report two years ago suggesting a connection there was a dramatic decline - from 90 per cent to 75 per cent - in the number of babies and young children being vaccinated.
Dr Farrington says he believes it would have been disastrous to allow the numbers to fall further:
"If that had continued then almost certainly we would have seen a resurgence in diseases such as measles. In the last epidemic before MMR 17 children died, but because vaccination programmes are so successful people don't see infectious diseases as a problem. The focus shifts away from the disease being the problem to the vaccine," he says.
Dr Farrington enjoys working on vaccine-related statistics because his results can impact directly on people's lives - for the better.
He is currently researching the spread of infectious diseases in the human population and looking at further new methods of statistical analysis. Also simmering away on the back burner is a book he is writing on Statistical Methods and Infectious Diseases.
"It's the book I would like to have had when I started work in this field - a recipe book for statisticians."