Autoimmune disorders after immunisation with Influenza A/H1N1 vaccines with and without adjuvant: EudraVigilance data and literature review

All suspected autoimmune disorders (AID) reported as adverse reactions to EudraVigilance from 1 October 2009 to 31 December 2010 for adjuvanted (Celtura™, Fluval P™, Focetria™ and Pandemrix™) and non-adjuvanted (Cantgrip™, Celvapan™ and Panenza™) pandemic Influenza A/H1N1 vaccines were analysed to determine whether adjuvanted vaccines were associated with higher reporting of AID than non-adjuvanted ones. AID were identified based on the corresponding MedDRA High Level Group Term. Reports of type 1 diabetes mellitus and multiple sclerosis were also included in the analysis. Causality was assessed based on WHO causality assessment for adverse events following immunisation and Brighton Collaboration criteria for Guillain-Barré syndrome (GBS), idiopathic thrombocytopenic purpura and acute disseminated encephalomyelitis. Of the 50,221 adverse reactions received in EudraVigilance for A/H1N1 vaccines (adjuvanted: 46,173, non-adjuvanted: 4048), 314 were AID (adjuvanted: 276, non-adjuvanted: 38). GBS was the AID with the highest number of reports (125, adjuvanted: 109, non-adjuvanted: 16). Reporting ratios as calculated by the percentages of AID amongst all reported adverse reactions were 0.60% (95% CI: 0.53-0.67) and 0.94% (95% CI: 0.64-1.24) for adjuvanted and non-adjuvanted vaccines, and were 0.26% (95% CI: 0.22-0.31) and 0.37% (95% CI: 0.18-0.56) in a restricted analysis based on diagnostic certainty, causal relationship and plausible temporal association. Reporting rates for all reports of AID using the estimated number of vaccinees as denominator were 6.87 (95% CI: 6.06-7.68) and 9.98 (95% CI: 6.81-13.16) per million for adjuvanted and non-adjuvanted vaccines, and 3.01 (95% CI: 2.47-3.55) and 3.94 (95% CI: 1.95-5.94) per million in the restricted analysis. These results do not suggest a difference in the reporting of AID between adjuvanted and non-adjuvanted A/H1N1 vaccines. In a literature review performed on 31 August 2011, GBS was also the AID the most frequently discussed in association with A/H1N1 vaccination; reporting rates were generally within expected background rates.