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Flu
Vaccines Not Effective
Just as governments around the world are stockpiling millions
of doses of flu vaccine and antiviral drugs in anticipation of
a potential influenza pandemic, two new surprising research papers
have found that such treatments are far less effective than previously
thought.
"The studies published today reinforce the shortcomings of our
efforts to control influenza," wrote Dr. Guan Yi, a virologist
at the University of Hong Kong, in an editorial that accompanied
the papers. The two studies were published early online by The
Lancet, the London-based medical publication, because of their
important implications for the coming flu season.
In one paper, international researchers analyzed all the data
from patient studies on the flu vaccine performed worldwide in
the last 37 years and discovered that vaccines showed at best
a "modest" ability to prevent influenza or its complications in
elderly people.
"The runaway 100 percent effectiveness that's touted by proponents
was nowhere to be seen," said Tom Jefferson, a researcher in Rome
with the Cochrane Vaccine Fields project, an international consortium
of scientists who perform systematic reviews of research data.
"There is a wild overestimation of the impact of these vaccines
in the community," he said. "In the case of a pandemic, we are
unsure from the data whether these vaccines would work on the
elderly."
In the second paper, researchers from the Centers for Disease
Control and Prevention in Atlanta found that influenza viruses,
particularly those from the dreaded bird flu strain, had developed
high rates of resistance to the only class of cheap antiviral
drugs available - drugs mainly used to treat flu once patients
have caught it. These resistance rates have increased rapidly
since 2003, particularly in Asia.
"We were alarmed to find such a dramatic increase in drug resistance
in circulating human influenza viruses in recent years," said
Dr. Rick Bright of the disease control centers. "Our report has
broad implications for agencies and governments planning to stockpile
these drugs for epidemic and pandemic strains of influenza."
Before 2000, almost no virus was resistant to the drug Amantadine.
By 2004, 15 percent of influenza A viruses collected in South
Korea, 70 percent in Hong Kong and 74 percent in China were impervious.
During the first six months of 2005, 15 percent of the influenza
A viruses in the United States were resistant, up from 2 percent
the year before. All human cases of the bird flu A(H5N1) strain
- which is still extremely rare in humans - have been resistant,
the researchers said.
The immediate implications of these finding are most ominous for
the developing world, because wealthier nations have been stockpiling
newer and vastly more expensive antiviral medicines, like Tamiflu,
which are effective against the disease but still under patent.
Even so, the research is alarming because it demonstrates how
quickly and unexpectedly flu viruses can become impervious to
medicines once they are put into common use, as they would be
in the case of a pandemic. Also, at their best, antiviral medicines
do not cure influenza. They reduce transmission of the disease
and lessen somewhat the symptoms and complications in people already
infected, including the high rate of associated pneumonias.
Called for comment, Dick Thompson, a spokesman for the World Health
Organization, said that the group could neither support nor deny
the findings of the analysis of vaccine studies at this point,
noting only that some specialists criticized the researchers for
"not including some important past studies" in their sample.
But the problem of resistance "is a finding that is being discussed
widely within the flu world and will bear careful monitoring,"
he said, noting that he was not aware of any country in the developing
world that had been able to stockpile the newer drugs.
Anticipating a possible flu pandemic caused by a variant of the
bird flu virus - which belongs to the influenza A group - countries
have been aggressively buying antiviral medicines and contracting
to purchase a flu vaccine against that strain, even though it
is still under development. The United States has ordered $100
million worth of vaccine, and Italy $43 million worth, for example.
The current bird flu virus does not spread easily - if at all
- from human to human, and so has little potential to become a
worldwide human scourge. But the World Health Organization has
warned that it could acquire that potential through a couple of
common biological processes, and that countries should prepare
for a possible wave of serious influenza.
The fact that the vaccine study showed that inoculations have
had only a modest effect in the elderly is particularly worrisome,
because this is a group that tends to suffer high rates of complications
and deaths from the disease and vaccination is the standard practice.
In people over 65, the vaccines "are apparently ineffective" in
the prevention of influenza, pneumonia and hospital admissions,
although they did reduce deaths from pneumonia a bit, by "up to
30 percent," the study says.
"What you see is that marketing rules the response to influenza,
and scientific evidence comes fourth or fifth," Dr. Jefferson
said. "Vaccines may have a role, but they appear to have a modest
effect. The best strategy to prevent the illness is to wash your
hands."
In terms of antiviral drugs, 30 countries have placed huge orders
for Tamiflu, the most popular newer more expensive antiviral medicine,
said Martina Rupp, a spokesman for Roche, the Swiss company that
makes it. The Dutch Health Ministry has ordered five million doses,
enough to treat one-third of the population. Britain has ordered
supplies to treat 15 million.
Researchers speculate that one reason resistance rates to the
older, cheaper antiviral drugs jumped so much starting in 2000
- and skyrocketed after 2002 - is that doctors in Asia started
prescribing the drugs far more widely after the advent of bird
flu in 1997 and sudden acute respiratory syndrome, or SARS, in
2002.
Reference
Source 133
September
21, 2005
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