Abstract
BackgroundStudies have shown a slight excess risk in Guillain-Barré syndrome (GBS) incidence associated with A(H1N1)pdm09 vaccination campaign and seasonal trivalent influenza vaccine immunisations in 2009–2010. We aimed to assess the incidence of GBS as a potential adverse effect of A(H1N1)pdm09 vaccination.MethodsA neurologist-led network, active at the neurology departments of ten general hospitals serving an adult population of 4.68 million, conducted GBS surveillance in Spain in 2009–2011. The network, established in 1996, carried out a retrospective and a prospective study to estimate monthly alarm thresholds in GBS incidence and tested them in 1998–1999 in a pilot study. Such incidence thresholds additionally to observation of GBS cases with immunisation antecedent in the 42 days prior to clinical onset were taken as alarm signals for 2009–2011, since November 2009 onwards. For purpose of surveillance, in 2009 we updated both the available centres and the populations served by the network. We also did a retrospective countrywide review of hospital-discharged patients having ICD-9-CM code 357.0 (acute infective polyneuritis) as their principal diagnosis from January 2009 to December 2011.ResultsAmong 141 confirmed of 148 notified cases of GBS or Miller-Fisher syndrome, Brighton 1–2 criteria in 96 %, not a single patient was identified with clinical onset during the 42-day time interval following A(H1N1)pdm09 vaccination. In contrast, seven cases were seen during a similar period after seasonal campaigns. Monthly incidence figures did not, however, exceed the upper 95 % CI limit of expected incidence. A retrospective countrywide review of the registry of hospital-discharged patients having ICD-9-CM code 357.0 (acute infective polyneuritis) as their principal diagnosis did not suggest higher admission rates in critical months across the period December 2009-February 2010.ConclusionsDespite limited power and underlying reporting bias in 2010–2011, an increase in GBS incidence over background GBS, associated with A(H1N1)pdm09 monovalent or trivalent influenza immunisations, appears unlikely.
Highlights
Studies have shown a slight excess risk in Guillain-Barré syndrome (GBS) incidence associated with A(H1N1)pdm09 vaccination campaign and seasonal trivalent influenza vaccine immunisations in 2009–2010
Among 141 confirmed of 148 notified cases of GBS or Miller-Fisher syndrome, Brighton 1–2 criteria in 96 %, not a single patient was identified with clinical onset during the 42-day time interval following A(H1N1)pdm09 vaccination
Three meta-analyses, one including US data obtained from six adverse event monitoring systems [9], a pooled analysis across databases from countries all over the world [10], and a meta-analysis of published reports [11] showed a 2–3 fold excess risk in GBS incidence associated with A(H1N1)pdm09 vaccines, both adjuvanted and non-adjuvanted, when compared to no vaccination
Summary
Studies have shown a slight excess risk in Guillain-Barré syndrome (GBS) incidence associated with A(H1N1)pdm vaccination campaign and seasonal trivalent influenza vaccine immunisations in 2009–2010. Mainly using self-controlled case series design [6] and self-controlled risk-interval design [7, 8], has addressed potential increases in GBS incidence after vaccination campaigns against the 2009 pandemic influenza A(H1N1). Three meta-analyses, one including US data obtained from six adverse event monitoring systems [9], a pooled analysis across databases from countries all over the world [10], and a meta-analysis of published reports [11] showed a 2–3 fold excess risk in GBS incidence associated with A(H1N1)pdm vaccines, both adjuvanted and non-adjuvanted, when compared to no vaccination. Only a US study assessed the potential increase over background GBS incidence following seasonal or A(H1N1)pdm influenza vaccines, with negative results[16], it remains to be seen if occurrence of GBS attributed to A(H1N1)pdm vaccination exceeded previous seasonal and monthly GBS estimates
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