Governments must be deadly serious regarding what they tell us Yet throughout history, immunisation campaigns have also inspired suspicion because of the fear that governments may place the interests of the state above those of the individual by exaggerating the benefits and minimising the risks. It was these fears that triggered the MMR scare, when people believed they were not getting the full facts about the MMR vaccine and its alleged link with autism, causing vaccination rates to plunge and measles infections to soar over the past decade. Medical experts held firm, the allegations of autism were eventually discredited and public trust has gradually been restored. But the episode illustrates the fragility of that trust. Now the Government's position is again under assault from what is claimed to be the most comprehensive review of the efficacy of the flu vaccine published anywhere in the world by the US Centre for Infectious Disease Research and Policy (Cidrap) and, separately, from the Cochrane Collaboration of experts. They say the vaccine is less effective than has been claimed, especially in the elderly, who are most at risk, because the immune response triggered by it varies in different age groups and because the protection provided depends on how well matched the vaccine is to circulating strains of the virus. Professor Michael Osterholm, the author of the "gold-standard" Cidrap study, absolves governments of deliberately misleading the public, on the grounds that the information about the vaccine's effectiveness has only recently become available. But, he says, they need to be "much more cautious" about what they say. The single most important currency governments have is public trust. If we lose that, we lose the most important currency for protecting public health," he says. Douglas Fleming, the British flu expert, echoes that view. Governments must give accurate and appropriate information about vaccines. It is a difficult message to convey: that the flu vaccine provides limited protection but is the best we have against what can be a deadly illness. However, the consequences of over-promoting it, in a desire to boost vaccination levels, risk doing untold damage to the most potent weapon the world has available against infectious disease.