by Alexandra Sifferlin
The link between the H1N1 vaccine and Guillain-Barré first emerged in 1976, during the U.S.’s last urgent national campaign to immunize 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 program was halted. H1N1 immunization was called for again in 2009, however, when threat of a related pandemic strain of influenza against which most of the population wasn’t immunized, 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 U.S. Department of Defense and Veterans Affairs, as well as a monitoring system specifically created to track adverse events related to the 2009 H1N1 immunization campaign. Researchers from the National Vaccine Program Office of the U.S. Department of Health and Human Services analyzed the data from 23 million people who were vaccinated as part of that effort and found 61 million cases of H1N1, 274,000 hospitalizations and 12,470 deaths related to the pandemic flu. Of those who were immunized, 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.
