By Simon Cox
Radio 4's The Report
A new vaccine for swine flu is most likely to be targeted at vulnerable groups such as young children and pregnant women. But a Radio 4 documentary has discovered that little or no data exists on the safety or effectiveness of flu vaccines on these groups.
There have been no trials of swine flu vaccines on pregnant women
In 1976 the US Government vaccinated 45 million people for a swine flu outbreak that never materialised.
But 500 people developed a rare neurological condition called Guillain-Barre syndrome syndrome which left people in a coma and 25 died.
The reaction still mystifies health officials, including Peter Smith, Professor of tropical epidemiology at the London School of Hygiene and Tropical Medicine.
"Why that happened has never really been understood - it's not really been observed with subsequent influenza vaccines," said Professor Smith, chairman of the global advisory committee on vaccine safety at the World Health Organisation.
"There's been a lot of seasonal flu vaccines and they've not seen this same adverse effect at all and so that is a sort of lurking shadow in the US experience which I suspect influences the way in which they treat all new vaccines," he added.
Health officials and academics think it is highly unlikely that such an adverse reaction would happen again.
But it is a concern as authorities around the globe stand on the verge of a mass vaccination programme against the current pandemic.
Pregnant women and children are expected to be among the groups targeted for vaccination, especially in countries likely to ration their vaccines.
Yet paradoxically the hard scientific evidence about the efficacy or dangers of these vaccines on pregnant women and young children does not exist.
"There is no study of the vaccines on pregnant women - no randomised clinical trials," said epidemiologist Tom Jefferson, who reviews influenza prevention and treatment for The Cochrane Collaboration, the voluntary global database provided by healthcare professionals which monitors the effects of healthcare worldwide.
He added: "Under the age of two there is only one trial and it shows inactivate vaccines [vaccines based on killed organisms] don't actually work."
Dr Jefferson said the best effect of influenza vaccines was on healthy adults.
A further problem, he explained, was that flu vaccines are unique in that they are registered and approved before full scale clinical trials have taken place.
Neither will the possible side effects be known on pregnant women or young children as Dr Marie Paul Kieny, director of vaccine research at the WHO explained. "It's not to say they would not be safe, they may be very safe but there is no data for the time being to demonstrate safety."
Adam Finn, professor of paediatrics at Bristol University is waiting for the go-ahead to commence a study the UK"
"We urgently need to get some evidence from children because young children, particularly under five, do seem to be at risk of serious illness," says Professor Finn.
"And secondly there is clear evidence that flu epidemics and pandemics are spread very efficiently by children. Children simply infect each other and their parents very efficiently and for that reason a hugely effective strategy to controlling epidemics of this kind is to immunise children."
Professor Finn predicted that the vaccines would probably be more effective in older children although he said that is not to say deploying the vaccines in younger children has no value.
"A vaccine that works, albeit not so well, is still better than no vaccine at all," he added.
The results of these trials will not be ready for a few months, probably mid-October.
This poses a potential dilemma for the Dept of Health - whether to start vaccination before the trial's results are known. Officials declined to tell The Report whether they will wait for the end of the trial.
The US has already issued its priorities: adults under 24, pregnant women, healthcare workers and people with underlying conditions like asthma. The over 65s are at the end of the queue.
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on BBC Radio 4, Thursday 6 August 2009 at 2000 BST. You can also listen via the BBC
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