(HealthDay News) – The monovalent inactivated influenza (H1N1) 2009 vaccine is associated with a small but significant increase in the risk of Guillain-Barré syndrome in the United States, according to a meta-analysis published online March 13 in The Lancet.
Daniel A. Salmon, PhD, from the Office of the Assistant Secretary for Health in Washington, DC, and colleagues conducted a meta-analysis of data from six adverse event monitoring systems, including about 23 million vaccinated individuals, to ascertain whether influenza (H1N1) 2009 monovalent inactivated vaccines are associated with an increased risk of Guillain-Barré syndrome.
The researchers found that vaccination with the influenza (H1N1) monovalent inactivated vaccine correlated with a small but significant increase in the risk of Guillain-Barré syndrome (incidence rate ratio, 2.35). This represented an excess of about 1.6 cases per million people vaccinated.
“Clinicians, policy makers, 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,” the authors write.