Monitoring adverse events of vaccines against Mexican flu.

In November 2009, a vaccination campaign against Influenza A (H1N1) was started in the Netherlands. The accelerated registration procedure of the vaccines used in this campaign and the use of these vaccines on a large scale indicated a need for real-time safety monitoring. This article looks at the way in which the safety monitoring of the pandemic influenza vaccines was organized in the Netherlands and it gives an overview of the main findings with respect to the two pandemic influenza vaccines, Focetria and Pandemrix, used in the Netherlands. Close monitoring, an efficient processing and analyzing the reports resulted in a close and real-time monitoring of the safety of the vaccines. From 1 November 2009 until 1 March 2010, 7534 reports concerning one or more events possibly related to the administration of both vaccines were received. 2788 of the reports related to Focetria and 4746 of the reports related to Pandemrix. No signals of possible batch-related problems were detected for either vaccine. The profile of the reported adverse events is comparable with the information provided in the Summary of Product Characteristics (SPC). Differences in reported events between both vaccines may be caused by bias and confounding due to the different populations for which these vaccines have been used.