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Slight risk for Guillain-Barré syndrome attributed to H1N1 vaccine
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Data from a meta-analysis show that there may be a slight risk for Guillain-Barré syndrome associated with the influenza A (H1N1) 2009 monovalent inactivated vaccine.
“This study suggests that there is a small risk of Guillain-Barré syndrome after influenza vaccine, but this small risk is greatly outweighed by the benefits of the vaccine,” Bruce Gellin, MD, director of the National Vaccine Program Office, told Infectious Diseases in Children. “These findings are generally consistent with previous studies; however, because the study included so many vaccinated people, we were able to identify a very small risk that smaller studies would have a hard time finding.”
Bruce Gellin
Gellin and colleagues used data from six different adverse event monitoring systems to conduct the analysis, which included approximately 23 million people who received the influenza A (H1N1) vaccine. They identified 77 cases of Guillain-Barré syndrome. The incidence rate ratio was 2.35 (95% CI, 1.42-4.01). When assuming a background rate of one case per 100,000 person-years, the rate ratio translated to 1.6 excess cases per 1 million vaccinations.
“These data should be reassuring to people that might have concerns about Guillain-Barré syndrome after influenza vaccines, given how small of a risk has been identified,” Gellin said. “However, scientists currently do not fully understand what causes Guillain-Barré syndrome, and so, at this time, there is no way to identify who will develop it after vaccination.”
In a press release, Daniel Salmon, PhD, MPH, of the National Vaccine Program Office, said that the safety and monitoring program for influenza A (H1N1) 2009 monovalent inactivated vaccine did not identify any other serious adverse events associated with the vaccine.
“About 61 million cases of influenza A (H1N1) disease were reported in the US during the 2009 pandemic, which included about 274,000 H1N1-related admissions and about 12,470 deaths,” Salmon said. “Clinicians, policymakers and those eligible for vaccination must consider the overall risks and benefits of vaccination, as defined by epidemiological studies, but should be assured that the benefits of influenza A (H1N1) 2009 monovalent inactivated vaccines greatly outweighed the risks.”
Disclosure: Salmon and Gellin report no relevant financial disclosures.
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