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Journal

Risk of Guillain-Barr� syndrome after seasonal influenza vaccination and influenza health-care encounters: a self-controlled study

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Published:25th Mar 2020

Background:

The possible risk of Guillain-Barr� syndrome from influenza vaccines remains a potential obstacle to achieving high vaccination coverage. However, influenza infection might also be associated with Guillain-Barr� syndrome. We aimed to assess the risk of Guillain-Barr� syndrome after seasonal influenza vaccination and after influenza-coded health-care encounters.

Methods:

We used the self-controlled risk interval design and linked universal health-care system databases from Ontario, Canada, with data obtained between 1993 and 2011. We used physician billing claims for influenza vaccination and influenza-coded health-care encounters to ascertain exposures. Using fixed-effects conditional Poisson regression, we estimated the relative incidence of hospitalisation for primary-coded Guillain-Barr� syndrome during the risk interval compared with the control interval.

Findings:

We identified 2831 incident admissions for Guillain-Barr� syndrome; 330 received an influenza vaccine and 109 had an influenza-coded health-care encounter within 42 weeks before hospitalisation. The risk of Guillain-Barr� syndrome within 6 weeks of vaccination was 52% higher than in the control interval of 9�42 weeks (relative incidence 1�52; 95% CI 1�17�1�99), with the greatest risk during weeks 2�4 after vaccination. The risk of Guillain-Barr� syndrome within 6 weeks of an influenza-coded health-care encounter was greater than for vaccination (15�81; 10�28�24�32). The attributable risks were 1�03 Guillain-Barr� syndrome admissions per million vaccinations, compared with 17�2 Guillain-Barr� syndrome admissions per million influenza-coded health-care encounters.

Interpretation:

The relative and attributable risks of Guillain-Barr� syndrome after seasonal influenza vaccination are lower than those after influenza illness. Patients considering immunisation should be fully informed of the risks of Guillain-Barr� syndrome from both influenza vaccines and influenza illness.

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