Prior to marketing of pandemic influenza vaccines, the only safety data
were those from clinical trials. The objective of this study was to
compare information coming from spontaneous reporting with that
systematically collected in a formal observation study; this also
permits to further evaluate safety of pandemic influenza vaccines in the
targeted patients' population. Out of a sample of 507 vaccinated
subjects, 103 (20.3%) developed some complication. In the same period 83
reports corresponding to all vaccinated people of Castilla y León (Spain)
(n=131,462) were collected. Severe cases were 1 (1%) and 7 (8.4%),
respectively, with the two procedures.
The spontaneous reporting rate
was 322-fold lower than that identified through the follow-up study;
when considered the severe cases, it was 37-fold lower. Under certain
circumstances reporting might be performing better than usual due to
strengthening of the surveillance system. Adverse events observed for
the pandemic H1N1 vaccines lie within the expected safety profile for
common events with influenza vaccines. An overall benefit-risk
assessment of these vaccines should be done.
http://www.ncbi.nlm.nih.gov/pubmed/21112311