Researchers at Laval University, Department of Pediatric Neurology (Dr Boucher), Quebec University Hospital and other centers in Montreal, Quebec, Canada assessed the risk of Guillain-Barre syndrome (GBS) following the pandemic influenza vaccination campaign in 2009, mostly using an AS03 adjuvant vaccine. Over a 6-month period, 83 confirmed GBS cases were identified and 25 had been vaccinated against 2009 influenza A (H1N1) 8 or fewer weeks before disease onset (most (19/25) were vaccinated 4 or fewer weeks before onset). Relative risk was 1.80 for all cases during the 8-week postvaccination period and 2.75 during the 4-weeks postvaccination. The number of GBS cases attributable to vaccination was 2 per 1 million doses. No confirmed case of GBS was reported in the immunized age group 6mo-9years; one case occurred in the 10-19 year old immunized group (rate 1.20 per 100,000 person-years). [1]

COMMENT. A small but significant risk of GBS was associated with the 2009 influenza A (H1N1) vaccination campaign in Quebec, Canada. In the US, results of the CDCs Emerging Infections Program showed a statistically significant association between nonadjuvant 2009 influenza A (H1N1) influenza vaccines and GBS [2]. The RR varied between 2.1 and 3.0; attributable risks were 1.5 – 2.8 per million doses administered. In the 1976- 1977 US epidemic, an unusually high rate of GBS followed the inactivated “swine” influenza A (H1N1) vaccination program. The variable risk of GBS with different H1N1 vaccines is an annual concern.

Increased vaccine-attributable risk for febrile convulsions following influenza vaccine [3]. Analysis of vaccine-attributable risk (VAR) was confined to children 6-59 months of age presenting to 9 Perth, Australia hospitals for management of a febrile convulsion in the 49 days between March 8, 2010, when the influenza vaccination program commenced and April 24, 2010, 48 hours after vaccinations for children were suspended. Ninety-nine children presented with febrile convulsions, 39 within 72 hours of receiving an influenza vaccine and 60 who had not been vaccinated. Of the 39 who had a febrile convulsion after influenza vaccination, 38 had received the 2010 vaccine, Fluvax. The total number receiving Fluvax in Perth metropolitan area was 11, 963. The 49-day risk of ED presentation for febrile convulsion following Fluvax was 38/11,963 or 32/10,000. The risk in those not receiving Fluvax was 7/10,000. The VAR as risk difference is 25/10,000. For the corresponding period in 2009 the VAR is estimated as zero. Further use of Fluvax was suspended in Australia.