Updated

British health officials have warned doctors of possible similarities between the new H1N1 vaccine and a shot linked to 25 deaths in the U.S. in the 1970s.

The British government’s Health Protection Agency (HPA), said in a letter to neurologists that they needed to look out for increases in cases of a brain disorder that might follow the launch of the immunization program.

The letter has been sent because of concerns sparked by studying of the swine flu vaccination campaign in the U.S.

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In 1976, Washington rushed in a mass immunization program against a similar swine flu outbreak that was confined to a single military base.

Several hundred cases of a rare, lethal, paralyzing neurological disease called Guillain-Barré syndrome (GBS) were reported afterwards, and although no clear link was ever found to the vaccine, the incident made many mistrustful of immunizations.

Although the H1N1 vaccine now close to completion is different from the one used in 1976, the HPA said the earlier incident nevertheless highlighted a possible area of concern.

"The vaccines used to combat an expected swine influenza pandemic in 1976 were shown to be associated with GBS and were withdrawn from use," Prof. Elizabeth Miller, head of the HPA’s immunization department, wrote in the letter sent last month to neurologists.

Click here for more on this story from the Sunday Times of London.