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INFLUENZA PANDEMIC (H1N1) 2009 (55): VACCINE FORMULATION
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A ProMED-mail post
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ProMED-mail is a program of the
International Society for Infectious Diseases
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In this update:
[1] Seasonal H1N1 vaccine dispensable?
[2] Seasonal H1N1 vaccine creates risk?
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[1] Seasonal H1N1 vaccine dispensable?
Date: Wed 23 Sep 2009
Source: Winnipeg Free Press, Canadian Press report [edited]
<http://www.winnipegfreepress.com/life/health/WHO-experts-say-it_s-safe-to-drop-old-H1N1-strain-from-seasonal-flu-shots-60723677.html>
Influenza experts have urged vaccine manufacturers to drop one of the
older strains of flu from the seasonal shot for next year's [2010]
Southern Hemisphere winter, saying there are so few of those viruses
around anymore they don't pose a significant public health threat.
But that good news was tempered by the panel's assessment of what is
happening with another family [serotype] of influenza A virus, the
H3N2s. Their recommendation of a new H3N2 component for the flu shot
suggests the Northern Hemisphere may be facing a vaccine mismatch, if
H3N2 viruses circulate much this winter [2009-2010]. "The predominant
H3N2 virus circulating at the moment is not that contained in the
Northern Hemisphere vaccine," said Gregory Hartl, a spokesperson for
the World Health Organization. The expert panel drew up the
recommendations for the WHO, which in turn advises countries and
vaccine manufacturers what should go in flu shots. No one knows how
big a role H3N2 viruses will play in the comi!
ng Northern Hemisphere flu season. But experts fear a double whammy;
a flu season started early in the fall with swine flu [pandemic
(H1N1) 2009 virus infection] followed by a wave of illness triggered
by H3N2 viruses. That would make for a long and nasty flu season.
H3N2 viruses typically cause more severe disease than seasonal H1N1
viruses. And they prey on the elderly, a group largely spared by
swine flu.
The WHO's experts, drawn from a network of key influenza laboratories
around the world, meet twice a year to make recommendations on which
strains of viruses manufacturers should include in flu shots. Because
it takes months to make and distribute flu vaccine, they meet well in
advance of the flu season. The meeting for the following Southern
Hemisphere winter takes place in September; the group will reconvene
in February to select the strains for the flu shot for the 2010-11
Northern Hemisphere winter. They pore over global virus circulation
patterns and reports of how similar or distinct new strains are
compared to those included in the most recent seasonal flu shots.
For the 2010 Southern Hemisphere winter, they recommended
manufacturers make vaccine to protect against 3 viruses, the pandemic
H1N1, a new H3N2 and an influenza B virus from a group of viruses
known as the Victoria lineage. But the group did not make a
recommendation on whether those 3 vaccines should be bundled into
one, the way the current seasonal shots are formulated, or whether
pandemic vaccine should remain separate and the seasonal shot should
contain only 2 components going forward. The WHO had asked the group
to leave that decision to another group, the Strategic Advisory Group
of Experts. The SAGE, as it's called, is set to meet in late October
2009.
Influenza experts have been keenly watching to see if the new H1N1
virus will follow the pattern of previous pandemic viruses and
replace existing influenza A viruses. The H1N1 virus that caused the
1918 pandemic disappeared when H2N2 materialized in 1957, triggering
the Asian flu pandemic. When H3N2 sparked the 1968 Hong Kong flu
pandemic, H2N2 viruses stopped circulating. But the dynamics this
time around are different. That's because since 1977, 2 influenza A
virus [serotypes] have co-existed in humans. That year H1N1 viruses
similar to those that had circulated before the 1957 pandemic
reappeared; the belief is a lab accident in Russia led to the release
of the viruses. They didn't cause a pandemic because there was so
much immunity to H1N1 viruses in people over about age 30. But the
viruses did manage to reseed [?] themselves and have shared the stage
with H3N2 viruses ever since.
Experts have been predicting the new H1 virus would supplant the old
one, a phenomenon that appears to be underway. But they are less
optimistic the pandemic virus can wipe out H3N2 viruses as well.
"Let's put it this way: If it's going to push out a strain, which I
suspect that it will, (seasonal) H1N1 would be the 1st candidate,"
Dr. Walter Dowdle predicted recently. Dowdle, the retired former head
of the influenza laboratory at the U.S. Centers for Disease Control,
has questioned whether the new virus has enough "muscle" to out
compete H3N2 viruses. If the experience of 1957 and 1968 can be used
as a guide, the world should know relatively quickly whether the
pandemic virus will replace the old influenza A viruses, he said. "It
took place essentially immediately. ... By the time the season was
over, it was very clear that there was no more of the previous virus
around."
Losing at least one of the old A viruses would be a relief, experts
say. Flu labs and vaccine manufacturers don't want to have to
contemplate the consequences of having 3 influenza A plus influenza B
viruses circulating at the same time. "Ideally in formulating the
vaccine, you'd like to deal with no more than 3 (components)," Dowdle
said. "You'd like to deal with no more than 2." "You would prefer not
to deal with 4."
If the pandemic virus manages to get rid of H3N2 as well as the old
H1N1, public health might actually come to think fondly of this
pandemic virus. Life would become a lot simpler, said Dr. Nancy Cox,
current head of the CDC's influenza division. "Our lives have been
really complicated by having so many different components in the
vaccine. If we could go back to a single A and a single B or even a
single A and 2 Bs, that would simplify our lives a lot."
[Byline: Helen Branswell]
--
Communicated by:
ProMED-mail <promed@promedmail.org>
******
[2] Seasonal H1N1 creates risk?
Date: Wed 23 Sep 2009
Source: CBC News, cbcnews.ca [edited]
<http://www.cbc.ca/health/story/2009/09/23/flu-shots-h1n1-seasonal.html>
Preliminary research suggests the seasonal flu shot may put people at
greater risk for getting swine flu [i.e. pandemic (H1N1) 2009 virus
infection], CBC News has learned. "There is some evidence that has
been floated. It hasn't been validated yet, it's very preliminary,"
cautioned Dr. Don Low, microbiologist-in-chief at Mount Sinai
Hospital in Toronto. "This is obviously important data to help guide
policy decisions. How can we best protect people against influenza?"
It's important to validate the information to make sure it's not just
a fluke and that the observation is confirmed elsewhere, such as in
the Southern Hemisphere, which just completed its seasonal flu
season, Low added.
Four Canadian studies involved about 2000 people, health officials
told CBC News. Researchers found people who had received the seasonal
flu vaccine in the past were more likely to get sick with the H1N1
[i.e. pandemic (H1N1)] virus.
Researchers know that, theoretically, when people are exposed to
bacteria or a virus, it can stimulate the immune system to create
antibodies that facilitate the entry of another strain of the virus.
Dengue fever is one example, Low said.
The latest finding raises questions about the order in which to get
flu shots. Across Canada, public health authorities are debating the
idea of shortening, delaying or scrapping their seasonal flu
vaccination campaign in favour of mass inoculation against H1N1
[pandemic (H1N1) 2009 virus]. The main reason is that H1N1 may be the
dominant strain of influenza circulating when the fall flu season
hits, meaning it could be a waste of time and resources to mount a
seasonal flu vaccine campaign.
Health authorities in Quebec are considering canceling or postponing
seasonal flu shots for some groups, such as healthy, younger adults.
The Public Health Agency of Canada says it's up to provinces and
territories to decide on when to roll out flu shots. "We don't know
with this year's [2009-2010] flu shot how it interacts with the
pandemic flu shot, so it's a worry," said Dr. Michael Gardam,
director of infectious diseases prevention and control at the Ontario
Agency for Health Protection and Promotion.
Seasonal flu could also appear after Christmas, said Dr. David
Scheifele, director of the vaccine evaluation centre at B.C. [British
Columbia] Children's Hospital in Vancouver.
--
Communicated by:
ProMED-mail Rapporteur Mary Marshall
[Notwithstanding the imminent onset of the Northern Hemisphere
influenza season and the predicted 2nd phase of the 2009 H1N1
pandemic, there still appears to be a lack of unanimity regarding the
best strategy to adopt to deal with the situation. - Mod.CP]
[see also:
Influenza pandemic (H1N1) 2009 (54): vaccine availability 20090921.3325
Influenza pandemic (H1N1) 2009 (53): vaccine donation 20090919.3290
Influenza pandemic (H1N1) 2009 (52): WHO update 66 20090918.3272
Influenza pandemic (H1N1) 2009 (51): antibody deficiency 20090917.3261
Influenza pandemic (H1N1) 2009 (50): oseltamivir-resistance 20090917.3260
Influenza pandemic (H1N1) 2009 (40): global update 20090906.3138
Influenza pandemic (H1N1) 2009 (30): assumptions 20090813.2879
Influenza pandemic (H1N1) 2009 (20): Peru, 33 percent asymptomatic
20090730.2668
Influenza pandemic (H1N1) 2009 (10): vaccine 20090720.2577
Influenza pandemic (H1N1) 2009 - Viet Nam: patient data 20090708.2450]
...................................................cp/msp/lm
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