Adverse Events with the Influenza A(H1N1) Vaccine Pandemrix® at Healthcare Professionals in Portugal

Abstract

Introduction: Healthcare professionals were a priority group for Pandemrix® vaccination. Surveying this particularly committed group for vaccination related side effects could help to get valuable information about vaccine safety profile. Our aim was to identify the adverse events following immunization with Pandemrix® among healthcare professionals. Material and Methods: A questionnaire for active post-authorization monitoring of adverse events following immunization with the influenza vaccine A (H1N1) was designed and distributed to the vaccinated healthcare professionals working at 3 elected hospital centres in the Northern region, in the period from 26 October 2009 to 31 January 2010. Results: From the 2358 vaccinated healthcare professionals that accepted to participate in this study, 864 (37%) returned back the fulfill questionnaire on time. Among these, 634 (73%) of healthcare professionals experienced at least one adverse event following immunization, but only 8% experienced an unexpected one. The adverse events most frequently reported were expected and very common: local reactions at the injection site (57%), myalgia (31%), fatigue (including asthenia) (24%) and headache (19%). No cases of major episodes, such as death or life-threatening events were reported. Female gender and existence of underlying conditions were independent risk factors to develop at least one adverse event following immunization to the pandemic vaccine. Conclusions: Our work suggests an acceptable safety profile of this pandemic flu vaccine among healthcare professionals. Both frequency and severity of the observed adverse event following immunization do not seem to be higher than expected.