As scientists delve deeper into H5N1 avian influenza,
they have discovered it is only three steps way from mutating into a
potentially lethal human pandemic form, adding new urgency to a debate over how
to protect humans.
In 2009, during the H1N1 swine flu pandemic, vaccines
only became available months after the virus had spread around the world - and
even then there was only enough for one in five of the world's 7 billion
people.
Next time, experts say, we need another approach.
Talk is centred on "pre-pandemic
vaccination" - immunising people years in advance against a flu pandemic
that has yet to happen, and may never come, rather than rushing to create
vaccines once a new pandemic starts.
"Even if you change manufacturing to higher-yield
technologies, you're still going to be chasing the virus," David
Salisbury, Britain's director of immunisation, who chaired a global group on
vaccines during the H1N1 flu pandemic, said in an interview.
"The bottom line is that current production will
never solve the problem. You'll always get at least one, if not two waves of
infection before you can get sufficient quantities of vaccine to do anything
significant ... If you want to get ahead of it, you've got to have a different
strategy."
Scientists and vaccine makers have already produced
pre-pandemic H5N1 vaccines and some are stockpiled by wealthy countries like
the United States and European governments for front-line medical staff.
Pharmaceutical companies have also invested heavily in
ramping up flu vaccine production capacity - partly due to the H1N1 pandemic
and partly in response to World Health Organisation (WHO) calls for better
preparedness for next time.
Annual flu vaccination programmes have also gained
impetus in recent years, with the result that seasonal campaigns are
well-established in many developed and some developing countries and structures
therefore exist to immunise lots of people.
So why not bring all those elements together and run a
pre-pandemic vaccination campaign to prime potential victims with a preparatory
shot?
IMMUNITY COULD LIMIT DEATH TOLL
This could boost the immunity of millions of people to
a pandemic bird flu strain that might otherwise kill tens of millions. The
1918-19 Spanish flu outbreak killed an estimated 20 million to 50 million
people worldwide.
The last flu pandemic was widely viewed as a mild
strain and the WHO, along with drugmakers and governments, was criticised in
some quarters for scare-mongering over the threat.
Yet a fresh analysis last month showed it may still
have killed as many as 580,000 people, far more than the 18,500 cited as the
number of laboratory-confirmed deaths.
A mutated human pandemic form of H5N1 bird flu could
be a whole different ball game. H5N1 does not yet pass easily from birds to
people but when it does it kills around 60 percent of those infected.
The virus continues to spread among birds in Asia,
with China reporting the latest cull of more than 150,000 chickens in the far
western region of Xinjiang just last week. As of July 6, the WHO counts 607
cases of people infected by bird flu globally. Of those, 358 died, a fatality
rate of 59 percent.
Faced with that risk, Rino Rappuoli, a scientist at
the Switzerland's Novartis - one of the several drugmakers including Sanofi and
GlaxoSmithkline that have H5N1 vaccines approved for use - made the case for
pre-pandemic vaccination in a paper in the journal Science last month.
"Given that licensed H5N1 vaccines are available,
we have the option to vaccinate individuals at greatest risk or to vaccinate
more broadly, including the populations of individual countries, of continents,
or even the entire globe," he wrote.
"It is just a question of evaluating the cost,
the logistics and the risk of implementing such a vaccination campaign. It is
not impossible."
A global campaign might take three to five years, he
said.
Pharmaceutical companies would certainly like a new
opportunity to put their flu vaccine manufacturing capacity to better use -
potentially triggering a re-run of the $7 billion-plus sales windfall seen in
2009-10.
During that pandemic, industry capacity was ramped up
to around 900 million doses, but to sustain this drug companies need a regular
flow of business and demand for flu vaccines is only around 480 million doses
right now.
PRIMING EFFECT
The scientific case for pre-pandemic vaccination looks
sound, given studies led by Karl Nicholson of Britain's Leicester University
showing that even people immunised with a different flu strain still had
"immune memory" and some protection from a new virus many years
later.
"It's called the priming effect," said Nikki
Shindo, a medical officer in the department of pandemic and epidemic diseases
at the WHO in Geneva.
In theory, at least, she said pre-pandemic vaccination
was "a great idea".
Shindo and other experts believe priming the immune
system has the potential to make the illness suffered by those who catch
pandemic flu far less severe, cutting the number of hospital admissions,
reducing death rates and possibly also slowing onward transmission of the
virus.
Getting the idea off the drawing-board, however, is
another matter and there appears to be limited appetite in government circles
right now for costly insurance-policy type vaccination.
That is perhaps understandable. Spending cash on a
health emergency that hasn't yet happened is politically tricky, particularly
in an age of austerity.
"I don't think the world would be ready to pay
for something like that now. The time is just not economically right,"
said Mark Clark, a pharmaceuticals industry analyst at Deutsche Bank.
As well as paying to protect against an as yet
non-existent disease, governments might also have an uphill battle persuading
the public to have a shot that could potentially cause mild fever, injection
site pain and the occasional allergic reaction.
"All of these strategies are worth thinking
about," said Salisbury, who like Clark thinks governments are a long way
yet from making a decision.
"It's got loads of common sense about it and it's
got loads of science behind it," he added. "But it is a big
step."
Kate Kelland and Ben Hirschler
(Editing by Philippa Fletcher)
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