Anaphylaxis following H1N1 pandemic vaccines: Safety data in perspective

We present here a detailed analysis of anaphylaxis cases reported to GlaxoSmithKline safety database following vaccination with its H1N1 pandemic influenza vaccines, Pandemrix™ and Arepanrix™. Cases were assessed according to the Brighton Collaboration Case Definition (BCCD) as either confirmed diagnosis (97/395, 24.6%), insufficient information to fulfil the minimal criteria of the case definition (117/395, 29.6%) or anaphylaxis excluded (181/395, 45.8%). There was no evidence that the rate of anaphylaxis following vaccination with Pandemrix™ or Arepanrix™ is increased with respect to the rates of anaphylaxis for other vaccines. Our analysis also highlighted the challenges of reliably determining the rate of anaphylaxis as an adverse event in the postmarketing setting following mass vaccination, as anaphylaxis was excluded in 45.8% of reported cases.