Guillain-Barré syndrome and A (H1N1) 2009 vaccine

British Medical Journal
16 July 2011 Volume 343, Issue 7815

Safety of adjuvanted pandemic influenza A (H1N1) 2009 vaccines
Frank DeStefano, Claudia Vellozzi, Lawrence B Schonberger, Robert T Chen
BMJ 2011;343:doi:10.1136/bmj.d4159 (Published 12 July 2011)

Risk of Guillain-Barré syndrome, if any, is smaller than for 1976 swine flu vaccines

Guillain-Barré syndrome has been a focus of safety monitoring since the report in 1976 of an increased risk of almost one extra case per 100 000 influenza vaccinations of swine origin. 1 Subsequent studies have shown either no increased risk or a slightly increased risk (1-2 per million vaccinees) after vaccination for seasonal flu. 2 The spread of the 2009 pandemic influenza A (H1N1) virus, which contained genes of swine origin, resulted in the development and widespread use of influenza A (H1N1) monovalent vaccines (2009 H1N1 vaccines). 3 These included formulations containing oil in water adjuvants that had not previously been widely used in flu vaccines in Europe. Although available evidence suggested that the adjuvanted vaccines had acceptable safety profiles, 3 data on the risk of rare adverse events, such as Guillain-Barré syndrome, were limited.

In the linked study (doi: 10.1136/bmj.d3908 ), Dieleman and colleagues report the first data on adjuvanted 2009 H1N1 vaccines and the risk of Guillain-Barré syndrome from a …

Guillain-Barré syndrome and adjuvanted pandemic influenza A (H1N1) 2009 vaccine: multinational case-control study in Europe
Jeanne Dieleman, Silvana Romio, Kari Johansen, Daniel Weibel, Jan Bonhoeffer, Miriam Sturkenboom, and the VAESCO-GBS Case-Control Study Group
BMJ 2011;343:doi:10.1136/bmj.d3908 (Published 12 July 2011)
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Objective  To assess the association between pandemic influenza A (H1N1) 2009 vaccine and Guillain-Barré syndrome.

Design  Case-control study.

Setting  Five European countries.

Participants 104 patients with Guillain-Barré syndrome and its variant Miller-Fisher syndrome matched to one or more controls. Case status was classified according to the Brighton Collaboration definition. Controls were matched to cases on age, sex, index date, and country.

Main outcome measures   Relative risk estimate for Guillain-Barré syndrome after pandemic influenza vaccine.

Results   Case recruitment and vaccine coverage varied considerably between countries; the most common vaccines used were adjuvanted (Pandemrix and Focetria). The unadjusted pooled risk estimate for all countries was 2.8 (95% confidence interval 1.3 to 6.0). After adjustment for influenza-like illness/upper respiratory tract infection and seasonal influenza vaccination, receipt of pandemic influenza vaccine was not associated with an increased risk of Guillain-Barré syndrome (adjusted odds ratio 1.0, 0.3 to 2.7). The 95% confidence interval shows that the absolute effect of vaccination could range from one avoided case of Guillain-Barré syndrome up to three excess cases within six weeks after vaccination in one million people.

Conclusions   The risk of occurrence of Guillain-Barré syndrome is not increased after pandemic influenza vaccine, although the upper limit does not exclude a potential increase in risk up to 2.7-fold or three excess cases per one million vaccinated people. When assessing the association between pandemic influenza vaccines and Guillain-Barré syndrome it is important to account for the effects of influenza-like illness/upper respiratory tract infection, seasonal influenza vaccination, and calendar time.