Lyme Disease - Scarce flu vaccine not designed for new strain New Zealand variety worries officials

Author

Scarce flu vaccine not designed for new strain New Zealand variety worries officials

JWissmille

2004-11-10, 4:08 am

http://www.sfgate.com/cgi-bin/artic...4/10/24/FLU.TMP
San Francisco Chronicle

Scarce flu vaccine not designed for new strain
New Zealand variety worries officials

Sabin Russell, Chronicle Medical Writer
Sunday, October 24, 2004

As Americans scramble for scarce doses of flu vaccine in hopes of warding
off the respiratory bug this winter, the wily influenza virus may have other
plans.

Through a natural process known as antigenic drift, a new strain of
influenza that can diminish the effectiveness of today's vaccine is already
emerging on the far side of the world.

A shortage of vaccine occurred when British regulators found contamination
problems at a Chiron Corp. factory in Liverpool, effectively wiping out
about half the U.S. supply. The shortage has triggered a run on the
remaining doses and a struggle by health authorities to keep the panic in
check.

Officials said last week they are optimistic that those who do manage to get
a flu shot will be protected. But predictions are impossible, given the way
the virus manages to dodge its attackers.

The emergent strain raising questions now is known as A/Wellington, named
after the New Zealand city where it was first detected.

"The flu season has been late this year, and it seems some people who have
been vaccinated have been hit by this changing strain,'' said New Zealand
Health Ministry flu chief Dr. Lance Jennings.

Like weather forecasters watching tropical storms, epidemiologists for the
World Health Organization track the ever-evolving strains of influenza. The
predominant flu virus around the globe right now is one called A/Fujian, and
the vaccine Americans are seeking today is a perfect match for it.

But A/Wellington is gaining ground. Tests suggest that 43 percent of recent
New Zealand flu cases spring from the new strain, or variants of it.

A/Wellington has even turned up about as far from the South Pacific as is
geographically possible: in Norway.

So convincing was the late season surge of A/Wellington that the WHO on Oct.
8 recommended that next year's flu vaccine for the Southern Hemisphere,
which is shipped in March, be reformulated to protect against it.

Dr. Nancy Cox, director of the Influenza Branch at the Centers for Disease
Control and Prevention, said there is no way of knowing whether the
A/Wellington strain will establish a beachhead in the United States this
winter.

"Influenza viruses are inherently unpredictable,'' she said in a telephone
interview.

One reason for concern is that laboratory animal tests suggest that the
current vaccine -- which targets A/Fujian -- is about two-thirds less
effective in stirring antibodies against A/Wellington than it is against the
targeted strain.

That does not mean, Cox emphasized, that the current flu shot would be
two-thirds less effective in actual use, should the A/Wellington strain turn
up in the United States. People who regularly receive flu shots, she said,
may have higher levels of antibody protection against influenza than the
laboratory animals.

"We would not anticipate that the Wellington strain will cause an enormous
problem,'' she said.

Doris Bucher, a flu vaccine expert at New York Medical college in Valhalla,
N.Y., said the animal tests on A/Wellington are actually encouraging because
they show that antibodies stirred up by today's vaccine will inhibit the new
strain.

"If Wellington rushed in and took over, people would have good protection
with the current vaccine,'' she said.

Bucher's lab specializes in developing strains of influenza that grow well
in eggs and hence serve as the basis for each year's flu vaccine made from
eggs. The current flu vaccine is made from a strain developed by her
laboratory, and she is working right now on an A/Wellington-like strain for
manufacturers who will make next year's vaccines.

When flu vaccines are well-matched to the prevailing flu strains, the shots
can prevent flu in 70 percent to 90 percent of vaccinated adults, according
to the CDC. Well-matched shots may prevent flu in only 30 percent to 40
percent of nursing home residents, but they can reduce the death rate from
influenza and pneumonia in that population by 80 percent.

Last year, the vaccine was a less than perfect match.

American manufacturers need a nine-month lead to produce flu vaccine. That
requires flu forecasters to predict in February what the prevailing flu
strain will be November.

In February 2003, the Food and Drug Administration's Vaccines and Related
Biological Products Advisory Committee selected a strain called A/Panama as
the target. Another strain, known as A/Fujian, was starting to emerge on the
World Health Organization's flu radar, but planners feared there was not
enough time to develop a vaccine for it.

Influenza struck the United States early and hard last year. The first cases
turned up in early October in Texas, and soon anxious Americans were
clamoring for vaccine -- a prelude to this year's flu shot frenzy.

A near-record 83 million eventually had a flu shot last fall. But the
predominant flu strain was not A/Panama -- it was A/Fujian. And the vaccine
was only partially effective.

A Colorado study for the CDC concluded last year's flu shots were 52 percent
effective in protecting healthy adults against flu, 38 percent effective in
preventing flu among those with health conditions putting them at higher
risk.

Bucher said it is reassuring that tests are showing there is less of a
mismatch between the current flu vaccine and A/Wellington than there was
last year between A/Panama and A/Fujian.

"It's nothing like the situation we had last year,'' she said.

The issue, of course, will be academic if the A/Fujian strain predominates
again this year -- as it did in the Southern Hemisphere during most of the
winter season that has now ended there. Those 61 million Americans who will
find a vaccine will be protected.

There is also some evidence that the A/Fujian strain -- having swept through
the globe last year -- may have lost its punch. Despite the late emergence
of the new flu strain, influenza was unusually mild throughout the Southern
Hemisphere from May through October.

One reason may be that the human population, vaccinated or not, developed
its own natural resistance to A/Fujian when it came through last winter.

"There are a number of factors that determine whether you will have a good,
medium or bad flu year, and clearly a major factor is whether the
predominant strain happens to be the same as the one the previous year,''
said Dr. Anthony Fauci, director of the National Institute of Allergy and
Infectious Diseases.

So far, there have been only isolated cases of flu detected in the United
States at the start of this year's flu season, and all have turned out to be
A/Fujian.

"Things are looking pretty good, in that regard,'' Fauci said. "But that
doesn't mean we won't get into trouble in November or December.

"It's much too early,'' he said. "to predict what kind of year we are going
to have.''

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supralover1994@gmail.com

2004-11-21, 11:20 am

Wellington is actually closely related to Fujian and so far all H3N2
isolates in the US that have been further sub-typed are Fujian-like.
The big challenge however is the H5N1 virus in Asia, which has a very
significant pandemic potential
http://www.recombinomics.com/pandemic_potential.html

supralover1994@gmail.com

2004-11-21, 11:20 am