Published Date: 2009-10-05 10:00:05
Subject: PRO/AH> Influenza pandemic (H1N1) 2009 (64): Canada, vaccination update
Archive Number: 20091005.3457
INFLUENZA PANDEMIC (H1N1) 2009 (64): CANADA, VACCINATION UPDATE
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Date: Sun 4 Oct 2009
Source: The Canadian Press (CP) [edited]
<http://www.google.com/hostednews/canadianpress/article/ALeqM5gPz7AwhAlmZF7pAyHmP0GWejWPHg>
No need to change vaccine policy based on Canadian flu data: WHO
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International influenza vaccine experts are apparently not convinced
that Canadian researchers have found a true link between getting a
seasonal flu shot and catching swine flu [see: ProMED-mail posting
"Influenza pandemic (H1N1) 2009 (59): Canada, vaccination
20090929.3400"]. The consensus that emerged from a World Health
Organization (WHO) teleconference Friday [2 Oct 2009] on the
controversial data seemed to be that the Canadian findings are likely
due to some confounding factor or factors in the data themselves and
may not reflect a real increased risk, according to a WHO official who
helped pull together the meeting.
"From a WHO point of view, the fact that the findings are not
replicated in other countries I think is reassuring for us that this
is an outlier, if you like, the unexpected findings that are coming
out of Canada," said David Wood, coordinator of the quality, safety,
and standards team of WHO's department of immunization, vaccines, and
biologicals. "Most people are still looking at this as some sort of
undetected confounding in the data, that for some reason is giving the
results that are there."
In an interview from Geneva, Wood was diplomatic. But when pressed, he
did admit most experts on the call didn't seem to believe that the
unpublished study, based on data from British Columbia, Quebec, and
Ontario, had found a true link between getting a seasonal flu vaccine
and having an increased risk of coming down with a mild case of H1N1
flu. "Well, yeah," he said. "It's a totally unexpected finding." "So I
think people do then try to think: 'Well, why is this happening? Are
there some effects that are just not being detected that are really
behind this?' Because it is an unexpected finding. That's the way
people tend to think."
The work, which is [reportedly] being considered for publication by a
medical journal, contributed to decisions by most provinces and
territories to stagger or delay their seasonal flu shot efforts this
fall [2009]. Instead of launching full-fledged seasonal flu vaccine
programs in October [2009], most have announced they will offer
seasonal shots in October only to seniors -- who aren't currently at
high risk from the pandemic H1N1 virus -- and residents of long-term
care facilities. After pandemic vaccination efforts are completed,
most of those provinces plan to offer seasonal vaccine more broadly.
A couple of jurisdictions -- Quebec and Nunavut -- will wait until
after they've completed their pandemic vaccination efforts before
offering seasonal flu shots. At the other end of the spectrum, New
Brunswick is going ahead with its regular seasonal flu shot campaign
before offering pandemic flu shots.
The Canadian findings, which are reportedly mirrored in data from
Manitoba as well, suggest that people who got a flu shot last fall
[2008] were twice as likely as people who didn't to contract swine
flu. But the association, if it is real, is to mild disease. There is
no evidence that people who got seasonal flu shots are more prone to
develop severe illness if they catch the new H1N1 virus.
Scientists from the United States, Britain, and Australia have looked
at their data but didn't see the same effect. A number of scientists
have speculated that the Canadian data may have some built-in
confounders -- factors that can produce false results. For instance,
if people who get flu shots are also more likely to seek a diagnosis
of swine flu if they get sick, that could make it seem like more of
them got the illness when in fact what happened is that more of their
illnesses were recorded.
But if the Canadian results are due to some statistical flaws or
selection biases, no one on the 4 1/2-hour teleconference was able to
put a finger on what exactly the problem is, Wood acknowledged. And he
admitted there may not be a satisfactory answer to that puzzle in the
foreseeable future. "It didn't seem very likely that we're going to be
able to ..... suddenly come up with the magic explanation as to why
the Canadian data are different to others," Wood said. "In the short
term, this is really probably as far as we're going to get."
New studies will likely be needed to get a definitive answer, he said.
Experts say there will need to be prospective studies -- following
people who get a flu shot forward -- rather than the retrospective
studies that produced the unusual findings. The evidence from
retrospective studies isn't considered as high quality as that
garnered from prospective studies.
In the meantime, a summary of the situation will be presented to the
WHO's Strategic Advisory Group of Experts on immunization, also known
as SAGE. The group, which meets later this month [October 2009], makes
recommendations for the WHO on vaccination policy. Wood said he
couldn't prejudge what the committee will decide, but said for the
moment it doesn't seem like the WHO needs to ask countries to change
their vaccination programs for this fall [2009]. "The fact that it's
just been seen in Canada at the moment, I don't think that that's
going to force global policy changes," he said.
[Byline: Helen Branswell]
--
Communicated by:
ProMED-mail Rapporteur Mary Marshall
[Previously in ProMED-mail [Influenza pandemic (H1N1) 2009 (59):
Canada, vaccination 20090929.3400] it was reported that: "British
Columbia might suspend seasonal flu shots as early as Monday 28 Sep
2009 for people who aren't seniors, in the wake of a Canadian study
that suggests people who get the normal flu vaccine are twice as
likely to contract H1N1 [pandemic 2009] virus infection. Researchers
found that those who received the seasonal flu vaccine in the past
were more likely to catch H1N1 [pandemic 2009 virus] infection.
Several provinces, including Quebec, Alberta, Saskatchewan, Ontario,
and Nova Scotia, have suspended seasonal flu shots for anyone younger
than 65, and Quebec will postpone regular flu shots until January
[2010] New Brunswick, on the other hand, announced last week that it
will stick to its plans to offer seasonal flu shots in October [2009]."
The report above indicates that the Canadian experience is exceptional
and has not been observed elsewhere. The factors responsible have not
been identified so far and the WHO recommends that other countries
should not amend their vaccination strategies. Publication of the
relevant Canadian data is awaited, and the WHO Scientific Advisory
Group of Experts (SAGE) will review the situation later in the month
(October 2009). - Mod.CP]
See Also
Influenza pandemic (H1N1) 2009 (63): USA military vaccine 20091002.3437Influenza pandemic (H1N1) 2009 (62): Taiwan hosp cases 20091001.3421
Influenza pandemic (H1N1) 2009 (61): FLAARDS 20091001.3419
Influenza pandemic (H1N1) 2009 (60): bacterial coinfection 20090930.3410
Influenza pandemic (H1N1) 2009 (59): Canada, vaccination 20090929.3400
Influenza pandemic (H1N1) 2009 (58): Netherlands, PB2 mutation 20090928.3394
Influenza pandemic (H1N1) 2009 (57): case counts 20090925.3367
Influenza pandemic (H1N1) 2009 (56): antiviral resistance risk 20090925.3363
Influenza pandemic (H1N1) 2009 (55): vaccine formulation 20090925.3359
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 20090917.321
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/mj/dk
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