Vaccination is the single greatest success story of 20th-century medicine. It has saved millions of lives around the world – from smallpox, polio, diphtheria, typhoid, tetanus, measles - and flu.
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 last 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 flu vaccine published anywhere in the world by the US Centre for Disease Research and Policy 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, author of the “gold standard” CIDRAP study absolves governments of deliberately misleading the public, on the grounds that the information about the vaccine’s effectivenss has only recently become available. But “from here on out”, 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. “In order to maintain public trust, Government’s must give accurate and appropriate information about vaccines including the extent of protection to be expected.”
It is a difficult message to convey: that flu vaccine provides limited protection but is the best we have against what can be a deadly illness. But 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.