title: Importance of background rates of disease in assessment of vaccine safety during mass immunisation with pandemic H1N1 influenza vaccines.
abstract: Because of the advent of a new influenza A H1N1 strain, many countries have begun mass immunisation programmes. Awareness of the background rates of possible adverse events will be a crucial part of assessment of possible vaccine safety concerns and will help to separate legitimate safety concerns from events that are temporally associated with but not caused by vaccination. We identified background rates of selected medical events for several countries. Rates of disease events varied by age, sex, method of ascertainment, and geography. Highly visible health conditions, such as Guillain-Barré syndrome, spontaneous abortion, or even death, will occur in coincident temporal association with novel influenza vaccination. On the basis of the reviewed data, if a cohort of 10 million individuals was vaccinated in the UK, 21.5 cases of Guillain-Barré syndrome and 5.75 cases of sudden death would be expected to occur within 6 weeks of vaccination as coincident background cases. In female vaccinees in the USA, 86.3 cases of optic neuritis per 10 million population would be expected within 6 weeks of vaccination. 397 per 1 million vaccinated pregnant women would be predicted to have a spontaneous abortion within 1 day of vaccination.
authors.affiliation: Center for Global Health and Division of Infectious Diseases, Cincinnati Children's Hospital, Cincinnati, OH, USA. Electronic address: Steven.Black1@cchmc.org.
authors.forename: Steven
authors.initials: S
authors.lastname: Black
authors.affiliation: National Institute for Health and Welfare, Helsinki, Finland.
authors.forename: Juhani
authors.initials: J
authors.lastname: Eskola
authors.affiliation: Center for Vaccinology and Neonatal Immunology, Department of Pediatrics, University of Geneva, Geneva, Switzerland.
authors.forename: Claire-Anne
authors.initials: CA
authors.lastname: Siegrist
authors.affiliation: Institute for Vaccine Safety, Department of International Health, Johns Hopkins Bloomberg School of Public Health, Baltimore, MD, USA.
authors.forename: Neal
authors.initials: N
authors.lastname: Halsey
authors.affiliation: Division of Infectious Diseases, Department of Pediatrics, Dalhousie University, Halifax, NS, Canada.
authors.forename: Noni
authors.initials: N
authors.lastname: MacDonald
authors.affiliation: Vaccine Safety Section, Centre for Immunization and Respiratory Infectious Diseases, Public Health Agency of Canada, Ottawa, ON, Canada.
authors.forename: Barbara
authors.initials: B
authors.lastname: Law
authors.affiliation: Health Protection Agency, Centre for Infections, Colindale, London, UK.
authors.forename: Elizabeth
authors.initials: E
authors.lastname: Miller
authors.affiliation: Health Protection Agency, Centre for Infections, Colindale, London, UK.
authors.forename: Nick
authors.initials: N
authors.lastname: Andrews
authors.affiliation: Health Protection Agency, Centre for Infections, Colindale, London, UK.
authors.forename: Julia
authors.initials: J
authors.lastname: Stowe
authors.affiliation: National Vaccine Program Office, Department of Health and Human Services, Washington, DC, USA.
authors.forename: Daniel
authors.initials: D
authors.lastname: Salmon
authors.affiliation: National Vaccine Program Office, Department of Health and Human Services, Washington, DC, USA.
authors.forename: Kirsten
authors.initials: K
authors.lastname: Vannice
authors.affiliation: Center for Biologics Evaluation and Research, Food and Drug Administration, Rockville, MD, USA.
authors.forename: Hector S
authors.initials: HS
authors.lastname: Izurieta
authors.affiliation: Center for Biologics Evaluation and Research, Food and Drug Administration, Rockville, MD, USA.
authors.forename: Aysha
authors.initials: A
authors.lastname: Akhtar
authors.affiliation: Discipline of Paediatrics, School of Paediatrics and Reproductive Health, University of Adelaide, SA, Australia.
authors.forename: Mike
authors.initials: M
authors.lastname: Gold
authors.affiliation: Department of Pediatrics, Faculty of Medicine, University of São Paulo, São Paulo, Brazil.
authors.forename: Gabriel
authors.initials: G
authors.lastname: Oselka
authors.affiliation: Quality, Safety and Standards Team, World Health Organization, Geneva, Switzerland.
authors.forename: Patrick
authors.initials: P
authors.lastname: Zuber
authors.affiliation: Quality, Safety and Standards Team, World Health Organization, Geneva, Switzerland.
authors.forename: Dina
authors.initials: D
authors.lastname: Pfeifer
authors.affiliation: Immunization Safety Office, Centers for Disease Control and Prevention, Atlanta, GA, USA.
authors.forename: Claudia
authors.initials: C
authors.lastname: Vellozzi
mesh_terms: D000293:Adolescent; D000328:Adult; D002675:Child, Preschool; D005260:Female; D020275:Guillain-Barre Syndrome; D006801:Humans; D053118:Influenza A Virus, H1N1 Subtype / Q000276:immunology*; D007252:Influenza Vaccines / Q000009:adverse effects / Q000592:standards*; D008297:Male; D032541:Mass Vaccination / Q000009:adverse effects; D009103:Multiple Sclerosis / Q000209:etiology; D009188:Myelitis, Transverse / Q000209:etiology; D009443:Neuritis / Q000209:etiology; D007752:Obstetric Labor, Premature / Q000209:etiology; D009902:Optic Neuritis / Q000209:etiology; D011247:Pregnancy
chemical_list: D007252:Influenza Vaccines