The reaction still mystifies health officials, including Peter Smith,
Professor of tropical epidemiology at the London School of Hygiene and
"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
"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
Yet paradoxically the hard scientific evidence about the efficacy or
dangers of these vaccines on pregnant women and young children does not
"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
Dr Jefferson said the best effect of influenza vaccines was on healthy
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
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
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,
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
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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