Risk of Guillain-Barre syndrome from H1N1 vaccine

The link between the H1N1 vaccine and Guillain-Barré first emerged in 1976, during the US’s last urgent national campaign to immunise citizens against a fast-acting flu.

At that time, the risk of the disease, which is a rare but serious immune disorder in which the body’s own immune cells start to attack nerves, leading to muscle weakness, paralysis and even death, was concerning enough that the vaccination programme was halted. H1N1 immunisation was called for again in 2009, however, when threat of a related pandemic strain of influenza against which most of the population wasn’t immunised, called for a massive vaccination campaign to avoid a pandemic. Now the latest study on adverse events reported from those vaccinations, published in the Lancet, shows that the risk of Guillain-Barré remained.

The data included adverse events reported to six different systems, including the core vaccine safety datalink, new surveillance systems established by Medicare and the US Department of Defense and Veterans Affairs, as well as a monitoring system specifically created to track adverse events related to the 2009 H1N1 immunisation campaign. Researchers from the National Vaccine Program Office of the US Department of Health and Human Services analysed the data from 23 million people who were vaccinated as part of that effort and found 61 million cases of H1N1, 274,000 hospitalisations and 12,470 deaths related to the pandemic flu. Of those who were immunised, 77 developed Guillain-Barré, some as long as 91 days after getting their shot. Since the disorder normally affects about one person in 100,000, this results in an additional 1.6 cases of Guillain-Barré syndrome per one million people vaccinated—still a small risk.

This rate is similar to that found in other studies that have studied the link between the vaccine and the autoimmune disorder. Last summer, a group of scientists in Quebec analysed the risk of Guillain-Barré syndrome in millions of people given the vaccine in Canada between 2009 and 2010 and reported 83 confirmed cases of Guillain-Barré, including 25 cases among people who received the H1N1 vaccine.

Reporting on the study last July, TIME wrote:

“The connection between H1N1 vaccines and Guillain-Barré first emerged during the swine flu pandemic in 1976, when public health experts ordered mass immunisations against an H1N1 influenza virus related to the one seen in 2009; health officials saw slight increases in the syndrome following the mass inoculations.

“After reviewing data on the link, the Institute of Medicine concluded that the vaccine was responsible for the increased risk of Guillain-Barré, and that some people were more susceptible to flu-shot-triggered cases than others. 

“Scientists said that by producing antibodies against the flu virus in response to the vaccine, some people may inadvertently generate antibodies against their own cells as well, causing the disorder.”

Older adults are more likely to develop the disorder and about 80 per cent recover completely with the proper treatment. According to the Centers for Disease Control, an estimated 3,000 to 6,000 Americans develop the disorder each year, regardless of whether they received a flu vaccine.(Time.com)

MORE INFO

• Guillain-Barré syndrome is an autoimmune disorder (the body’s immune system attacks itself). Exactly what triggers Guillain-Barré syndrome is unknown. The syndrome may occur at any age, but is most common in people of both sexes between ages 30 and 50.
It often follows a minor infection, such as a lung infection or gastrointestinal infection. 
Guillain-Barré syndrome damages parts of nerves. This nerve damage causes tingling, muscle weakness, and paralysis. Guillain-Barré syndrome most often affects the nerve’s covering. Such damage is called demyelination, and it causes nerve signals to move more slowly. Damage to other parts of the nerve can cause the nerve to stop working altogether.
 (MedlinePlus))

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