Vaccination has long been one of the greatest weapons in the battle against a range of potentially fatal diseases. Millions of lives have been saved worldwide, and Britain has played a major role in helping to combat new pandemics. But, rarely, things do go wrong and people develop serious side-effects. In the UK, the Government's Vaccine Damage Payment Scheme is supposed to help those left severely disabled as a result. Among those currently arguing their case are the families of children who developed an incurable and devastating sleep disorder after being immunised against swine flu. But, to date, most have received nothing and Ministers have now gone to the Court of Appeal to try and establish a less generous interpretation of the pay-out rules. Lawyers for the families say the whole scheme is outdated and unfit for purpose. Are they right? Jenny Chryss investigates. Reporter: Jenny Chryss Producer: Ruth Evans.