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H1N1 Vaccine Risks

What risks are associated with the H1N1 vaccine?
There is limited information available about adverse events associated with the H1N1 vaccine because the clinical trials are still in progress (as of October 21st 2009 only two small clinical trials in adults have been conducted).(28)

Once vaccination begins, the Public Health Agency of Canada has declared they will prepare a weekly report summarizing the adverse events reported in Canada on Fightflu.ca.(29)

GlaxoSmithKline is the manufacturer of the AREPANRIX™ vaccine and they have identified the following reactions with their product:

Very common (may occur with more than 1 in 10 doses, are usually mild and only last one or two days):

  • Pain at the injection site
  • Headache
  • Fatigue
  • Redness or swelling at the injection site
  • Shivering
  • Sweating
  • Aching muscles, joint pain

Common (may occur with up to 1 in 10 doses):

  • Reactions at the injection site such as bruising, itching and warmth
  • Fever
  • Swollen lympth nodes
  • Feeling sick, diarrhea

Uncommon (may occur with up to 1 in 100 doses):

  • Dizziness
  • Generally feeling unwell
  • Unusual weakness
  • Vomiting, stomach pain, uncomfortable feeling in the stomach or belching after eating
  • Swollen lympth nodes
  • Tingling or numbness of the hands or feet
  • Shortness of breath
  • Pain in the chest
  • Itching, rash
  • Pain in the back or neck, stiffness in the muscles, muscle spasms, pain in extremity such as leg or hand

Rare (may occur with up to 1 in 1000 doses):

  • Allergic reactions leading to a dangerous decrease of blood pressure, which, if untreated, may lead to shock. Doctors are aware of this possibility and have emergency treatment available for use in such cases
  • Fits
  • Severe stabbing or throbbing pain along one or more nerves
  • Low blood platelet count which can result in bleeding or bruising
  • Low blood platelet count which can result in bleeding or bruising

Very Rare (may occur with up to 1 in 10,000 doses):

  • Vasculitis (inflammation of the blood vessels which can cause skin rashes, joint pain and kidney problems)
  • Neurological disorders such as encephalomyelitis (inflammation of the central nervous system), neuritis (inflammation of nerves) and a type of paralysis known a Guillain-BarrŽ Syndrome(30)

According to the Public Health Agency of Canada, the average rate of adverse reaction of any vaccine is 1 in 100,000 vaccines distributed(31). The number of vaccines actually administered to Canadians is not currently tracked in Canada, therefore the average rate is likely more than 1 in 100,000 since some of the doses delivered to clinics and hospitals are not administered.

The systems in place to maximize vaccine safety include regulatory bodies, clinical trial requirements for licensing, post-licensing surveillance, and research. For more information, please review vaccine safety information from the Public Health Agency of Canada at www.phac-aspc.gc.ca/im/vs-sv/caefiss-eng.php.

In spite of these checks and balances, a number of safety issues remain such as underreporting of serious vaccine complications, lack of long-term safety studies, few randomized placebo-controlled trials, conflicts of interest, little independent evaluation of vaccine safety and lack of safety guidelines for vaccine components.

Page Last Updated: November 4, 2009

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