Flu Shot Unable to Combat Virus Strain
Mon Dec 15, 9:34 AM ET Add Health - AP to My Yahoo!
By DANIEL Q. HANEY, AP Medical Editor
Late last winter, a committee of vaccine experts designing this
season's flu shot considered their choices. They had two, and both
seemed bad.
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Should they stick with last year's formula, even though a new strain
of the bug was ominously building strength? Or should they try to make
a new vaccine and risk complications or delays that could result in a
shortage or maybe even no vaccine at all?
In the end, the committee voted 17-1 to bring back last year's
version, even though they feared they were telling millions of
Americans to roll up their sleeves for shots that might not work very
well.
Many of them probably agreed with Dr. Theodore Eickhoff of the
University of Colorado, who said: "For the first time in many years of
participating in these deliberations, I must add I am very
uncomfortable with the recommendation."
What Eickhoff and the others dreaded is exactly what happened. That
new strain of flu became the dominant variety, accounting for
three-quarters of all cases as the disease got an unusually early
start this fall.
About 83 million doses of vaccine were made, but no one really knows
how much protection from illness it gives. It almost certainly will
not be the usual 70 percent to 90 percent, and some experts fear it is
below 50 percent.
"We agonized. We asked repeatedly 'Is there another choice?'"
remembered Dr. David Stephens, who chaired the panel and heads
infectious diseases at Emory University. "The bottom line is, we
weren't really given a choice."
Their experience shows the frustrating and often imprecise nature of
humanity's labor to stay ahead of this perennial nuisance and sometime
killer.
The flu virus mutates constantly. The Food and Drug Administration
(news - web sites), with the help of its expert committee, must decide
in late winter what varieties will be the biggest threats. Picking the
best combination is a mixture of science, luck and seat-of-the-pants
instinct.
"By the time you know what's the right strain, you can't do anything
about it," said Dr. Michael Decker, head of scientific affairs at
Aventis, one of the three U.S. vaccine makers.
The first inkling of something worrisome dawned on flu experts at the
end of January. Just two weeks before committees were scheduled to
meet at the World Health Organization (news - web sites) in Geneva and
the FDA in Rockville, Md., to settle on the makeup of this fall's
vaccine, scientists who track the flu noticed a new strain was
gathering mass.
The vaccine could theoretically protect against several strains of the
virus, but because production is slow, the shot is limited to just
three. Any of these flu bugs can make people very sick, but since it
emerged in 1968 the one most likely to result in pneumonia or death is
a type called H3N2.
Flu viruses are categorized according to the makeup of their two key
proteins, hemagglutinin and neuraminidase, the "H" and "N" in their
names. Changes in the virus' hemagglutinin is especially troublesome,
since this is the protein the human body aims for when it makes
antibodies to fight off the flu.
For five years, the vaccine had protected against an H3N2 strain
called Panama. Now that virus had mutated. A version with two
differences in its hemagglutinin was causing outbreaks in Asia and had
also turned up in Europe and North America.
The FDA's committee met in February and heard the bad news: The
current vaccine might not reliably keep people from catching this
emerging strain, called Fujian.
Nobody knew if the new strain would die out or gain strength, but Dr.
Roland Levandowski, the FDA's flu vaccine expert, warned that new flu
variants sometimes spread rapidly.
The WHO — which makes vaccine recommendations to countries which set
their own vaccine standards — had already postponed its decision on
H3N2. The FDA committee did the same.
When the FDA committee met again in March, the situation was, in some
ways, even worse. Ten 10 percent to 20 percent of H3N2 viruses around
the world were Fujian. But the Centers for Disease Control and
Prevention (news - web sites) was having trouble isolating a sample
that could be the basis of a vaccine.
"This is a very urgent issue," CDC flu chief Nancy Cox told the
committee. "We've been working on this very intensively for what seems
like a very long time. We're very disappointed."
Still ahead were many other steps, as well. The Fujian strain's
hemagglutinin and neuraminidase genes would have to be transferred
into tame flu viruses that grow nicely in hens' eggs so vaccine makers
could produce them in bulk. Even then, it would take weeks to know if
the process would reliably generate the vast quantities needed.
"It became, Do we go with a vaccine we know will be partially
effective?" remembered Eickhoff. "Or do we wait around and try to
identify a possible candidate strain?"
When the vote came, only Peter Palese, head of microbiology at Mount
Sinai School of Medicine in New York, chose to switch to the Fujian
strain despite the unknowns. He worried that an ineffective formula
would give the flu vaccine a bad name because many people might get
sick.
The WHO made the same decision as the FDA. In hindsight, was it
correct?
Decker recalled what happened in 2000. Delays resulting from a switch
to a new strain, along with a virus that produced poorly, contributed
to a vaccine shortage.
A last-minute change to Fujian this year "could easily have meant not
only a severe shortage but also the wrong vaccine," he said. "Right
now, people are saying, 'You idiot, why didn't you choose Fujian?' But
what if Fujian had petered out?"
___
EDITOR'S NOTE: Medical Editor Daniel Q. Haney is a special
correspondent for The Associated Press.
___
On the Net:
Meeting transcripts:
http://www.fda.gov/ohrms/dockets/ac/03/transcripts/3922t1.doc
http://www.fda.gov/ohrms/dockets/ac/03/transcripts/3941t1.doc