INFLUENZA PANDEMIC (H1N1) 2009 (64): CANADA, VACCINATION UPDATE

Archive Number 20091005.3457
Published Date 05-OCT-2009
Subject PRO/AH> Influenza pandemic (H1N1) 2009 (64): Canada, vaccination update

 

INFLUENZA PANDEMIC (H1N1) 2009 (64): CANADA, VACCINATION UPDATE *************************************************************** A ProMED-mail post <http://www.promedmail.org> ProMED-mail is a program of the International Society for Infectious Diseases <http://www.isid.org>  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 ---------------------------------------------------------------- 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 But when pressed, he   did admit most experts on the call didn't seem to believe that the   unpublished study, based on data from British Columbia, Quebec, and   Ontario, had found a true link between getting a seasonal flu vaccine   and having an increased risk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]

 

Rispondi

Privacy Policy