# 5359
Late last week several Australian newspapers carried press reports on concerns expressed by Peter Collignon, a Professor of Infectious Diseases and Microbiology at the Australian National University, on the possibility that getting the seasonal flu shot may have increased the likelihood of contracting the 2009 pandemic strain.
Coverage included:
Rethink flu vaccine policy, says health expert
Adam Cresswell,
Health Editor From: The Australian March 04, 2011
Vaccines may have increased swine flu risk
By Annie Guest: ABC News
As you might imagine, these claims have sparked considerable concern and controversy.
Although all of the facts are not in, and the data is – at best – contradictory, this morning I thought we’d take a look at Professor Collignon’s concerns.
Ironically, after years of hearing from critics that flu vaccines are ineffective, the problem may be that the seasonal flu vaccine worked too well.
First a bit of background. Regular readers will be somewhat familiar with the following:
In the fall of 2009, news of an unpublished Canadian study began to surface that suggested that those who had received a seasonal flu shot the previous year were more likely to contract the new pandemic virus than those who hadn’t.
Helen Branswell, science and medical reporter for the Canadian Press, was among the first to report on it (see Branswell On The Canadian Flu Shot Controversy).
With many Canadian provinces just days away from starting up their seasonal flu vaccination campaigns while they awaited the arrival of the pandemic vaccine later in the fall, this was a bombshell.
Suddenly, there was genuine concern that maybe . . . just maybe . . . with a pandemic virus on the way, that rolling out the seasonal vaccine was the wrong thing to do.
The CDC and the World Health Organization both looked at their data, and issued statements that they could find no correlation between the seasonal vaccination and increased susceptibility to the pandemic flu . . . but that they would continue to look.
Meanwhile, with concerns rising, a number of Canadian Provinces halted or announced delays in rolling out the seasonal flu shot, even though the study had yet to be published (see Ontario Adjusts Vaccination Plan).
October saw a number of new reports and studies that failed to support the `Canadian problem’, including a study published in the BMJ (British Medical Journal) that suggested exactly the opposite.
It postulated that getting the seasonal flu vaccination may have been slightly protective against the swine flu (see When Studies Collide).
This, admittedly, ran contrary to what we’d heard from the CDC, who maintained that the seasonal vaccine was not expected to offer any protection against the novel H1N1 swine flu virus.
By November, with no further evidence of the `Canadian Problem’, Canada’s National Advisory Committee on Immunization (NACI) came out in favor of resuming seasonal flu jabs (see NACI: Canada Should Resume Seasonal Flu Vaccinations).
The controversy didn’t go away, however.
In April of 2010 the Canadian study was finally published by PLoS Medicine. Writing for CIDRAP, Maryn McKenna detailed their findings.
New Canadian studies suggest seasonal flu shot increased H1N1 risk
Maryn McKenna
Contributing Writer
Apr 6, 2010 (CIDRAP News) – Despite a rapidly launched range of studies, investigators in Canada are still unable to say—or to rule out—whether receiving a seasonal flu vaccination in the 2008-09 season made it more likely that Canadians would become ill from 2009 pandemic H1N1 flu.
Other studies, however, failed to show any correlation, leaving us with a bit of a mystery on our hands.
In November of last year, an article appeared in the Eurosurveillance Journal that suggested that contracting seasonal flu (as opposed to being vaccinated against it) temporarily ramped up the body’s immune system against other viruses – and that this protective effect could last months.
Eurosurveillance, Volume 15, Issue 47, 25 November 2010
Perspectives
H Kelly , S Barry, K Laurie, G Mercer
Unlike the Canadian researchers, Australian scientists could find no increased susceptibility to the pandemic H1N1 virus among those who had been vaccinated the previous year against seasonal flu.
The difference between the two findings, they suggest, comes from three separate factors:
- A theory regarding temporary immunity following any influenza infection
- The timing of the arrival of the pandemic virus in Canada
- And the protective effects of seasonal flu vaccination against seasonal - but not pandemic - flu.
In Canada, the first wave of the virus arrived on the heels of the 2008-2009 seasonal flu epidemic, which had peaked only 3 months earlier. Australia, however, was nearing the end of their summer, and the peak of their flu season had occurred a full 9 months before.
If the temporary immunity theory was correct (`if’ being the operative word), Canadians who had contracted seasonal flu earlier in the year, might still have carried some generic immunity against infection.
Australians, on the other hand, saw the pandemic virus arrive long after any such temporary protective benefits would have decayed.
This temporary immunity – which some scientists believe may be a linked to the theory of OAS (Original Antigenic Sin) – is not well understood. Complex, and deserving of a blog of its own, I won’t go into detail on OAS today, since we’ve discussed it before:
EID Journal: Original Antigenic Sin And Pandemic H1N1
In December of 2010, in the journal Clinical Infectious Diseases, we saw another study – this time in Hong Kong – that looked at the potential interaction between the 2008 seasonal vaccine, influenza infection, and the 2009 pandemic flu.
Benjamin J. Cowling,Sophia Ng, Edward S. K. Ma, Calvin K. Y. Cheng, Winnie Wai, Vicky J. Fang, Kwok-Hung Chan, Dennis K. M. Ip, Susan S. Chiu, J. S. Malik Peiris and Gabriel M. Leung
Conclusions. TIV protected against strain-matched infection in children. Seasonal influenza infection appeared to confer cross-protection against pandemic influenza. Whether prior seasonal influenza vaccination affects the risk of infection with the pandemic strain requires additional study.
Once again, evidence to suggest that catching the seasonal flu during the winter of 2008-2009 was somewhat protective against contracting the pandemic in the months following.
Which brings us back to Professor Collignon, who is suggesting that we should reassess our vaccination policies.
He argues that it may be better for healthy adults to get the seasonal flu – and develop more robust temporary immunity against potentially emerging viruses – than to routinely get the flu jab.
This is a controversial stance, and one that is not widely shared by researchers, scientists, and public health officials.
Arguing for the seasonal flu vaccine are that even healthy adults can suffer serious illness from influenza, and that any broad viral immunity from contracting seasonal flu is likely short-lived – probably measured in months, not in years.
When you add the fact that novel (pandemic) viruses emerge infrequently, the case for getting the annual flu shot grows stronger.
For now, the Temporary Immunity Hypothesis remains an intriguing, but as-yet unproven theory.
For those who like their science neat and tidy, devoid of ambiguity, and rock solid . . . all of this is no doubt a bit disconcerting. But this is how scientific progress works.
Slowly, deliberately, and not always advancing in a linear fashion. Simply put, good science takes time.
While I find all this quite thought provoking - and absolute truths are always elusive - unless and until more compelling data to the contrary comes forth, I intend to get my flu shot every year.
Call it a calculated risk.
After all . . . a pandemic may occur once every couple of decades, but seasonal flu comes around every year.
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