[1] US FDA, Ctr Biol Evaluat & Res, Div Epidemiol, Off Biostat & Epidemiol, Rockville, MD 20852 USA
[2] US FDA, Ctr Biol Evaluat & Res, Div Vaccines & Related Prod Applicat, Off Vaccines Res & Review, Rockville, MD 20852 USA
[3] Ctr Dis Control & Prevent, Immunizat Safety Branch, Epidemiol & Surveillance Div, Natl Immunizat Program, Atlanta, GA USA
[4] Ctr Infect Dis Prevent & Control Hlth Canada, Immunizat Safety Unit, Immunizat & Resp Infect Div, Ottawa, ON, Canada