The Expected Number of Background Disease Events during Mass Immunization in China

PLoS One
[Accessed 24 August 2013]
http://www.plosone.org/

The Expected Number of Background Disease Events during Mass Immunization in China
YouXin Wang, LiJuan Wu, XinWei Yu, FeiFei Zhao, Alyce Russell, ManShu Song, Wei Wang
Research Article | published 20 Aug 2013 | PLOS ONE 10.1371/journal.pone.0071818

Abstract
It is critical to distinguish events that are temporarily associated with, but not caused by, vaccination from those caused by vaccination during mass immunization. We performed a literature search in China National Knowledge Infrastructure and Pubmed databases. The number of coincident events was calculated based on its incidence rate and periods after receipt of a dose of hypothesized vaccine. We included background incidences of Guillain-Barré syndrome, anaphylaxis, seizure, sudden adult death syndrome, sudden cardiac death, spontaneous abortion, and preterm labour or delivery. In a cohort of 10 million individuals, 7.71 cases of Guillain-Barré syndrome would be expected to occur within six weeks of vaccination as coincident background cases. Even for rare events, a large number of events can be expected in a short period because of the large population targeted for immunization. These findings may encourage health authorities to screen the safety of vaccines against unpredictable pathogens.