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This year's flu vaccine: Setting things straight

Posted Oct 03 2011 6:01pm
There is so much written that is dead wrong about this year's flu vaccine,  another post is needed.  Here are some facts

1.  This year's flu vaccine is the same as last year's vaccine.  If you are healthy and got the vaccine last year, you probably still have antibodies against all 3 strains.

2.  The antigen used for the 2009 Swine Flu vaccine was an H1N1 hemagglutinen.  It was used as a single antigen vaccine in 2009, but was included as one of the three hemagglutinin antigens in 2010 and 2011.  In 2009, in some contries, a novel adjuvant was added to the antigen (either MF59 [Novartis] or ASO3 [Glaxo]) to increase the immune response.

In the US, for example, which used no adjuvant, the 2010 and 2011 flu vaccines contain the 2009 swine flu vaccine, plus two more antigens.  Therefore, claims that this year the vaccine is entirely different are misleading.

In countries like Ireland and England, which used the ASO3 adjuvant in 2009, the current flu vaccine differs from 2009 because it has no ASO3.  But it does have the same hemagglutinin adjuvant.

Narcolepsy cases have occurred after both adjuvanted and unadjuvanted swine flu vaccines were given.

3.  How effective is the vaccine?  Although 70-90% of recipients develop antibodies, the amount of flu that is prevented is questionable.  Remember that studies from Hong Kong and Canada found that if you got flu vaccine in 2008, you were about twice as likely to become ill with a swine flu infection the next year?  The effectiveness of the vaccine varies from year to year, but it is not very high, and never over 70% for the young and healthy.  It is hard to show any efficacy in the aged. 

4.  The reason narcolepsy was discovered to be a side effect of swine flu vaccine in Finland was  because there were 13 times as many cases appearing as usual.  That is 1300% more cases than expected, of a very serious condition that can have lethal consequences.

5.  Was narcolepsy the only serious adverse reaction to swine flu vaccine?  It's unlikely.

You may have seen headlines that swine flu vaccine does not cause Guillain Barre Syndrome ; I did, on the same day a report was issued about narcolepsy and the vaccine.  However, It seems it DOES cause Guillain Barre Syndrome after all.  The full text is here , or you can read the abstract below.  CDC calculated it caused 1.77 times as many cases of GBS as expected, or 177%.

MMWR Morb Mortal Wkly Rep. 2010 Jun 4;59(21):657-61.
Guillain-Barré syndrome (GBS) is an uncommon peripheral neuropathy causing paralysis and in severe cases respiratory failure and death. GBS often follows an antecedent gastrointestinal or upper respiratory illness but, in rare cases, can follow vaccination. In 1976, vaccination against a novel swine-origin influenza A (H1N1) virus was associated with a statistically significant increased risk for GBS in the 42 days after vaccination (approximately 10 excess cases per 1 million vaccinations), a consideration in halting the vaccination program in the context of limited influenza virus transmission. To monitor influenza A (H1N1) 2009 monovalent vaccine safety, several federal surveillance systems, including CDC's Emerging Infections Program (EIP), are being used. In October 2009, EIP began active surveillance to assess the risk for GBS after 2009 H1N1 vaccination. Preliminary results from an analysis in EIP comparing GBS patients hospitalized through March 31, 2010, who did and did not receive 2009 H1N1 vaccination showed an estimated age-adjusted rate ratio of 1.77 (GBS incidence of 1.92 per 100,000 person-years among vaccinated persons and 1.21 per 100,000 person-years among unvaccinated persons). If end-of-surveillance analysis confirms this finding, this would correspond to 0.8 excess cases of GBS per 1 million vaccinations, similar to that found in seasonal influenza vaccines. No other federal system to date has detected a statistically significant association between GBS and 2009 H1N1 vaccination. Surveillance and further analyses are ongoing. The 2009 H1N1 vaccine safety profile is similar to that for seasonal influenza vaccines, which have an excellent safety record. Vaccination remains the most effective method to prevent serious illness and death from 2009 H1N1 influenza infection; illness from the 2009 H1N1 influenza virus has been associated with a hospitalization rate of 222 per 1 million and a death rate of 9.7 per 1 million population.
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