The vaccine is meant to protect people with asthma by desensitizing them to allergens -- such as animal fur or dust -- that cause them to suffer an asthma attack. That's achieved by injecting them with minute amounts of the offending substance, BBC News Online reports.

This basic approach is not new, but has previously been dangerous because it carried the risk of causing a serious asthma attack.

The British scientists believe they've created a safe vaccine by modifying the protein allergens -- the basic ingredients of the vaccine. They divided the protein allergens into smaller units.

These smaller units are less likely to cause a serious asthma attack. But they're still large enough to be recognized by the immune system, which is essential in reducing sensitivity to asthma triggers, the scientists say.

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-- Robert Predit, Scott Roberts and Jean Patman