The 2009 influenza A(H1N1) “swine flu” vaccine, which was administered to millions of people around the world, is associated with a “small but significant risk” of Guillain-Barré Syndrome, an uncommon paralyzing nerve disorder, scientists from Quebec, Canada, reported in JAMA (Journal of the American Medical Association). The authors added that they believe the benefits of immunization outweighed the risks.
Guillain-Barré syndrome is a very uncommon but serious autoimmune disorder that damages the peripheral nervous system. The syndrome is typically caused by an acute infectious process. The peripheral nervous system refers to the nerves in the body outside the brain and spinal cord. A person affected with Guillain-Barré syndrome will initially have a tingly and numbing sensation in the limbs, usually the lower part of the legs; there will also be weakness in those areas. Often the sensations spread to the entire body and the patient becomes paralyzed.
As background information, the authors wrote:
“The disease is thought to be autoimmune and triggered by a stimulus of external origin. In 1976-1977, an unusually high rate of GBS was identified in the United States following the administration of inactivated ‘swine’ influenza A(H1N1) vaccines. In 2003, the Institute of Medicine (IOM) concluded that the evidence favored acceptance of a causal relationship between the 1976 swine influenza vaccines and GBS in adults. Studies of seasonal influenza vaccines administered in subsequent years have found small or no increased risk.
In a more recent assessment of epidemiologic studies on seasonal influenza vaccines, experimental studies in animals, and case reports in humans, the IOM Committee to Review Adverse Effects of Vaccines concluded that the evidence was inadequate to accept or reject a causal relationship.”
The researchers explained that in the Autumn of 2009, in Quebec, public health authorities launched an immunization campaign against the A(H1N1) pandemic strain, using mostly an AS03 adjuvant vaccine. By the end of 2009 approximately 57% of Quebec’s 7.8 million residents had received the vaccine.
Philippe De Wals, M.D., Ph.D., of Laval University, Quebec City, and team set out to determine what the risk of Guillain-Barré syndrome was after the shots were administered.
The team carried out a population-based cohort study with follow-up for a period of six months, from October 2009 to the end of March 2010.
Data were gathered from all neurology clinics and acute care hospitals in Quebec of suspected and confirmed Guillain-Barré syndrome (GBS) cases which had been reported by doctors, the majority of them neurologists during active surveillance. They also examined summary discharge databases of provincial hospitals. They also checked immunization status of the reported cases.
The investigators identified 83 confirmed cases of GBS over the six-month period. Twenty-five of them had been immunized against 2009 influenza A(H1N1) up to eight weeks before GBS onset – 19 of the 25 had been vaccinated within 4 weeks before onset.
After analyzing the data, the researchers concluded that there was “a small but significant risk of BGS following influenza A(H1N1) vaccination”.
They attributed 2 GBS cases for every 1 million doses.
The authors emphasized that the higher risk of developing Guillain-Barré syndrome was only higher among people aged 50 years or more.
The authors wrote:
“In Quebec, the individual risk of hospitalization following a documented influenza A(H1N1) infection was 1 per 2,500 and the risk of death was 1/73,000. The H1N1 vaccine was very effective in preventing infections and complications. It is likely that the benefits of immunization outweigh the risks.”
In the USA, approximately 1 to 2 people per 100,000 are affected by Guillain-Barré syndrome, says the CDC (Centers for Disease Control and Prevention). Just over 1,500 people in Great Britain are diagnosed annually with Guillain-Barré syndrome, out of a population of 62 million. As mentioned above, GBS is a rare disease. It is slightly more common in men than in women, and can affect people of all ages.
Swine flu, also referred to as swine influenza, pig influenza, pig flu and hog flu is a disease of pigs – an extremely contagious respiratory disease caused by one of several Influenza A viruses. From 1% to 4% of pigs that become infected with swine influenza virus die from the infection.
The most common swine influenza virus is of the H1N1 influenza subtype, but can be from other types, such as H1N2, H3N1, and H3N2.
The 2009 swine flu pandemic that infected humans was of the H1N1 type – not a very virulent (dangerous) type. The WHO (World Health Organization) declared the swine flu pandemic officially over in August 2010.
The World Health Organization says that the 2009/2010 H1N1 “swine flu” pandemic killed 18,500 people worldwide. However, a recent report published in The Lancet believes the total may be up to fifteen times higher. (Link to article)
Written by Christian Nordqvist