[Source: The Lancet Infectious Diseases, full text: (LINK). Abstract, edited.]
The Lancet, Early Online Publication, 13 March 2013
Association between Guillain-Barré syndrome and influenza A (H1N1) 2009 monovalent inactivated vaccines in the USA: a meta-analysis
Dr Daniel A Salmon PhD a c, Michael Proschan PhD d, Richard Forshee PhD e, Paul Gargiullo PhD f, William Bleser MSPH a, Dale R Burwen MD e, Francesca Cunningham PharmD g, Patrick Garman PhD h, Sharon K Greene PhD i, Grace M Lee MD i, Claudia Vellozzi MD f, W Katherine Yih PhD i, Bruce Gellin MD a, Nicole Lurie MD b, the H1N1 GBS Meta-Analysis Working Group†
The influenza A (H1N1) 2009 monovalent vaccination programme was the largest mass vaccination initiative in recent US history. Commensurate with the size and scope of the vaccination programme, a project to monitor vaccine adverse events was undertaken, the most comprehensive safety surveillance agenda in the USA to date. The adverse event monitoring project identified an increased risk of Guillain-Barré syndrome after vaccination; however, some individual variability in results was noted. Guillain-Barré syndrome is a rare but serious health disorder in which a person's own immune system damages their nerve cells, causing muscle weakness, sometimes paralysis, and infrequently death. We did a meta-analysis of data from the adverse event monitoring project to ascertain whether influenza A (H1N1) 2009 monovalent inactivated vaccines used in the USA increased the risk of Guillain-Barré syndrome.
Data were obtained from six adverse event monitoring systems. About 23 million vaccinated people were included in the analysis. The primary analysis entailed calculation of incidence rate ratios and attributable risks of excess cases of Guillain-Barré syndrome per million vaccinations. We used a self-controlled risk-interval design.
Influenza A (H1N1) 2009 monovalent inactivated vaccines were associated with a small increased risk of Guillain-Barré syndrome (incidence rate ratio 2·35, 95% CI 1·42—4·01, p=0·0003). This finding translated to about 1·6 excess cases of Guillain-Barré syndrome per million people vaccinated.
The modest risk of Guillain-Barré syndrome attributed to vaccination is consistent with previous estimates of the disorder after seasonal influenza vaccination. A risk of this small magnitude would be difficult to capture during routine seasonal influenza vaccine programmes, which have extensive, but comparatively less, safety monitoring. In view of the morbidity and mortality caused by 2009 H1N1 influenza and the effectiveness of the vaccine, clinicians, policy makers, and those eligible for vaccination should be assured that the benefits of inactivated pandemic vaccines greatly outweigh the risks.
US Federal Government.
a National Vaccine Program Office, Office of the Assistant Secretary for Health, Department of Health and Human Services, Washington, DC, USA; b Assistant Secretary for Preparedness and Response, Department of Health and Human Services, Washington, DC, USA; c Institute for Vaccine Safety, Johns Hopkins Bloomberg School of Public Health, Baltimore, MD, USA; d National Institutes of Health, Bethesda, MD, USA; e Food and Drug Administration, Rockville, MD, USA; f Centers for Disease Control and Prevention, Atlanta, GA, USA; g Department of Veterans Affairs, Hines, IL, USA; h Department of Defense, Washington, DC, USA; i Department of Population Medicine, Harvard Medical School and Harvard Pilgrim Health Care Institute, Boston, MA, USA
Correspondence to: Dr Daniel Salmon, Institute for Vaccine Safety, Johns Hopkins Bloomberg School of Public Health, Baltimore, MD 21205, USA
† Members listed at end of report