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Explainer: flu season 2012

Each year, different strains of influenza cause varying rates of illness throughout the community. So what strains are around this year and what kind of protection is offered by seasonal influenza vaccines…

The H3 strain of influenza has made a come back but immunity from past infectious is likely to have waned. Tranchis

Each year, different strains of influenza cause varying rates of illness throughout the community. So what strains are around this year and what kind of protection is offered by seasonal influenza vaccines? Robert Booy, Professor and Head of Clinical Research at the University of Sydney’s National Centre for Immunisation Research, explains.

Is this year’s flu season worse than usual?

Diagnostic laboratories in most states have reported higher rates of influenza notifications than the previous two years, so it’s the worst since 2009.

We suspect two reasons for this: first, with cooler and colder weather, people have spent more time indoors with others and have therefore been more likely to pass on infections.

Secondly, the main strain this winter is no longer H1, it’s H3. This strain has been quiet for a couple of years, meaning there’s likely to have been some fall off in background immunity from past infection. There’s also been some mutation – changes to the structure of the H3 – so the antibodies people have are less effective than they were.

Who is most at risk from this strain of influenza?

You’re most at risk of influenza when you’re very young or very old. Young children and babies are most likely to be hospitalised and people over the age of 75 are most likely to die from influenza. On average each year there are about 2,500 deaths from influenza in Australia, the large majority of them among the elderly.

On average, the H3 strain of flu is more severe than the other two strains (H1 or B) but all three can be deadly.

The H1 strain, which arrived as a new pandemic in 2009, preferentially affected people under the age of 60 because they didn’t have past exposure to H1 and had limited cross-protection from previous infection. So we had much more infection in younger people. But because their underlying health was better, the death rate was lower.

The H1 did, however, disproportionately affect some other groups such as pregnant women, in whom there were many severe infections resulting in intensive care and even the loss of pregnancies.

What strains of influenza does this year’s seasonal flu vaccination protect against?

The standard flu vaccine protects against three strains: two types of flu A (H1 and H3) and one type of flu B. The main strain causing disease this year is H3 and we have evidence from laboratory evaluations that the vaccine covers this year’s strain of H3. So we can expect that people who are vaccinated will be protected to at least the 75% level.

Year to year, the protection from a flu vaccine can vary from 50 and 90% but it usually settles out at around the 75% level.

How have attitudes to influenza changed since the swine flu pandemic?

People are definitely more aware of influenza and there’s no doubt that our testing facilities are more robust. Over the past five years there’s been a lot more testing for influenza in Australia, so the amount of disease detected can be higher for two reasons: an actual surge in the incidence and more frequent testing.

Who should get the flu vaccination – what do the government guidelines say?

The annual flu vaccine is recommended for anyone over the age of 65 or Indigenous Australians over the age of 50 and anyone above the age of six months who has a chronic medical condition which may include disorders of the heart, lung, kidney, liver, diabetes, immunosuppression and steroid treatment. The list also includes pregnant women.

Anyone who wants to be vaccinated can obtain this through their GP.

Less than half of young Australians with a high-risk condition have had either the flu vaccine or pneumonia vaccine. A higher vaccination rate would not only directly protect high-risk people, it would increase herd immunity.

What are the symptoms of influenza and when should you seek medical care?

Most people who get influenza actually get it as a relatively mild cold: perhaps 20% get it more severely, with a high fever, sore throat, muscle and headaches, and prostration (not being able to get out of bed). If you have those symptoms within 24 to 48 hours of falling ill your GP may prescribe an anti-viral therapy, but it only works early on in disease.

If you’ve been ill for longer and you have symptoms of an increased breathing rate, chest pain, cough and high fever, you may be developing pneumonia and could benefit from seeing the GP for antibiotic treatment.

Make sure you get plenty of rest and stay hydrated. Symptomatic treatments, such as over-the-counter products, may make you feel better but they’re not curative.

Further reading:
See more Explainer articles on The Conversation.

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15 Comments sorted by

    1. Matthew Wakefield

      logged in via Twitter

      In reply to Laurie Willberg

      A double-blind challenge study will not change the effectiveness of the the vaccine, it would only provide more evidence of this effectiveness. The basic properties of the vaccine will not be changed just by observing its effects.

    2. Roger Davidson

      not really a Student

      In reply to Laurie Willberg

      The Cochrane Review has the smell of the anti-vaccine crowd about it, especially when they devote space to discussions on "following the money".

      Has this research been peer-reviewed?

    3. Grendelus Malleolus

      Senior Nerd

      In reply to Laurie Willberg

      Attempting to follow some of the links in the article Laurie provided led to either the generic Cochrane collaboration pages or to a splash page indicating that the page linked to from the article does not exist - makes it very hard to fact check when Laurie's source has no visible supports.

    4. Stephen Prowse

      Research Advisor

      In reply to Laurie Willberg

      I just had a quick look at the summaries of 2 Cochrane reviews. As far as I can tell they make little distinction between flu caused by the influenza virus and infections with flu like symptoms caused by non-influenza viruses. Of course the influenza vaccine will not protect against the latter. Influenza vaccines offer good protection against a homologous virus but the influenza rapidly mutates so the virus in the community will never be the exactly the same as the virus in the community so protection will be variable. Unfortunately, a lack of understanding of this complexity is fodder for the anti-vaccine lobby. Vaccination still remains the best way of preventing influenza along with many other vaccine preventable diseases.

    5. Sue Ieraci

      Public hospital clinician

      In reply to Laurie Willberg

      Here is an excellent review of the topic, which discusses the reasons why reduction in death in the elderly has been found tobe more modest than initially projected (though still significant):

      This is how science works: it is a continual effort to improve.

      Homeopathy, OTOH, remains buried in the outdated theories of the nineteenth century.

  1. Elizabeth Hart

    Independent Vaccine Investigator

    Billions of people have gone through their lives without flu vaccination, yet in recent years we are all continually being pestered to have flu vaccinations every year. Is this really justifiable or effective? Has any research been done on the possible ill-effects of repeated annual vaccination throughout life, on top of the ever-expanding children’s vaccination schedule(1)?

    There are some very alarming things happening in the influenza industry, not the least of which is the US NIH funding…

    Read more
    1. Sue Ieraci

      Public hospital clinician

      In reply to Elizabeth Hart

      Elizabeth Hart - perhaps you have not noticed that, as our health outcomes and longevity continue to improve, as a community, our risk tolerance lowers and our expectations rise.

      So, in the past, everyone accepted not only the flu but also measles, mumps, chicken pox, death in childbirth and a whole range of risks and disabilities as part of life. Our community no longer accepts this - it is no lonoger accepted that some babies and mothers should die giving birth, or that some boys get infetility…

      Read more
    2. Lisa Hodgson


      In reply to Sue Ieraci


      Elizabeth made some very good points on vaccinations schedules and the newly discovered recombining virus in poultry. You have not addressed any?

      As far as the community goes they are captured by industry fear-mongering.

      Eg. the swine flu 'pandemic' The EU PACE committee charged the WHO body that declared the pandemic as being largely consisting of parties with vested interests in pharma. The whole episode was a massive con job. This pandemic cost Australians over $10 million in wasted…

      Read more
    3. Mark Amey

      logged in via Facebook

      In reply to Lisa Hodgson

      I don't think it was just 'fear-mongering' for the patients who required ventilation in ICU from 'swine-flu'!

  2. David Hill

    logged in via Facebook

    For many decades now we have known that due to the constant mutations of viruses, that what was good one year was not necessarily good for the next as last year's virus with a few tweaks had circumvented the antibodies that prevailed the year before. That is why when one studies the Spanish Flu and the 2009 Swine Flu some chilling facts come out with regard to fighting pandemics on the total reliance in many ways of providing antidotes (vaccines). Indeed when we study the Spanish Flu we determine…

    Read more
  3. Elizabeth Hart

    Independent Vaccine Investigator

    Further to my previous post on this topic.
    The US Centers for Disease Control and Prevention (CDC) / Department of Health and Human Services (HHS) recently called for submissions on “Influenza Viruses Containing the Hemagglutinin from the Goose/Guangdong/1/96 Lineage”. This is relevant to the H5N1 controversy.
    21 submissions have been posted so far on the website:!docketBrowser;rpp=25;po=0;dct=PS;D=CDC-2012-0010
    For information here’s a link to my submission to the CDC/HHS which I have titled “Opposition to Lab-engineering of Potentially Lethal Pathogens”:
    When is the media going to do its job and expose the massive international influenza racket?