THE 1998 Lancet paper which sparked off public concern about the MMR jab, is etched in my mind.

Not that I have a particular interest in the controversy, though I am alarmed about the effect on vaccination rates. It's just that I had to review the paper for a public health exam. There were 12 hours of writing, over two days. In the last session of the second sweltering June day, in the centre of London, I had to pick over the study, commenting on its strengths and weaknesses, the implications of the findings and formulating a public health response. Quite a challenge !

The paper is in the headlines again. This time, because it is claimed that at the time, lead researcher Dr Wakefield, was also being paid to investigate possible grounds for legal action by parents of children allegedly damaged by vaccination.

This clearly raises the possibility of a conflict of interest that could have introduced bias, even sub-consciously, into his research.

But such potential conflicts of interest do occur from time to time in research.

The real problem is that if the funding allegation is true, it was not disclosed when the paper was published.

This omission would represent a serious error of judgement on the part of Dr Wakefield.

A public health colleague no doubt has another paper etched in his mind, as a result of sitting the same exam a few weeks ago.

The research to be reviewed on that occasion was an analysis of the health impact of passive smoking, as a result of living with a smoker.

Published in the prestigious British Medical Journal last year, the paper concluded that passive smoking is not harmful.

However, this research seems to have had very little effect in changing the consensus of scientific opinion that passive smoking increases the risk of lung cancer and heart disease by about 25 per cent in non-smokers who live with smokers.

One big difference between the papers is that the BMJ now has a policy requiring all contributors to declare any potential conflict of interest.

At the end of the passive smoking paper the authors declared some of their research to be funded by tobacco companies.

Interpreting the results of scientific research needs to consider the context in which it is carried out.

Honest declaration of potentially conflicting interests is a healthy development.