Researchers at Cardiff University say preventing a form of diabetes could become a reality, if trials prove successful.
It aims to slow - or stop - the destruction of insulin-making cells using a vaccine-type treatment.
In the UK, Type 1 diabetes is on the increase.
David Wood reports.
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More than a thousand riders will be taking part in a series of events in and around the town.
Some warm spells of sunshine will develop, although scattered heavy and thundery showers are also expected during the afternoon.
A yellow 'be aware' warning has been issued by the Met Office for much of Wales.