Last Updated: 2003-05-23 10:05:47 -0400 (Reuters Health)

LONDON (Reuters Health) - Britain's medicines agency has condemned as "seriously flawed" a study showing that measles mumps and rubella (MMR) vaccination is associated with a greater risk of autism than diphtheria, tetanus and pertussis (DTP) vaccination.

The study, by U.S. geneticist Dr. Mark Geier and his son, David Geier, based in Silver Springs, Maryland, was widely publicised this week in Britain, where controversy has raged for years over the safety of the triple MMR jab.

It uses data from the United States Vaccine Adverse Event Reporting System, and estimates of doses of MMR and DTP vaccines distributed, to calculate the relative risk of autism and other brain conditions following MMR and DTP vaccination.

The results, published in the journal International Pediatrics, suggest that almost 25 million first doses of MMR were given in the US between 1994 and 2000, compared with 63 million for DTP.

Yet there were 29 reports of autism among boys and eight among girls following MMR -- five times more than with DTP.

British anti-MMR campaigners said the findings vindicated their warnings that MMR vaccination was associated with the rising number of children being diagnosed with autism.

But Professor Alasdair Breckenridge, chairman of the Medicines and Healthcare Products Regulatory Agency, said in a statement: "In no way are the conclusions of the authors of this study justified.

"These data simply cannot be used to determine whether an adverse event is causally linked to vaccination. The data in this study have been misused and the methodology is seriously flawed."

The agency said the study failed to take into account the limitations and biases of the data, including the possibility that adverse events were reported because of publicity about an alleged adverse reaction.

It noted that in the U.S., DTP vaccine is given at 2, 4, 6 and 15-18 months and MMR is first given at 12-15 months. "It is essential that children of similar age are compared," according to the statement. "Indeed, age imbalances in the groups would be sufficient to make the results invalid."