This Swedish retrospective cohort study, published in BMJ, examined the risk of neurological and autoimmune disorders in people vaccinated against pandemic influenza A (H1N1) with Pandemrix (GlaxoSmithKline) compared with unvaccinated people over 8-10 months.

Image of the H1N1 Influenza Virus, CDC.

One million people were vaccinated against H1N1 and 900,000 remained unvaccinated.

Excess risks among vaccinated people were of low magnitude, but present, for:

- Bell’s palsy (hazard ratio 1.25)
- paresthesia (1.11)
- inflammatory bowel disease (IBD)

Risks for Guillain-Barré syndrome, multiple sclerosis, type 1 diabetes, and rheumatoid arthritis remained unchanged.

The risks of paresthesia and inflammatory bowel disease (IBD) among those vaccinated in the early phase (within 45 days) of the vaccination campaign were significantly increased; the risk being increased within the first 6 weeks after vaccination.

The risks were small but significant among more than one million vaccinated, but only in high risk groups targeted for early vaccination and who were likely to have earlier comorbidity.

The absolute risk of Bell’s palsy was low, 6.4 cases per 100?000 vaccinated population.

References:

Neurological and autoimmune disorders after vaccination against pandemic influenza A (H1N1) with a monovalent adjuvanted vaccine: population based cohort study in Stockholm, Sweden. BMJ 2011; 343:d5956 doi: 10.1136/bmj.d5956 (Published 12 October 2011).

Source:
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