title: Measuring vaccine confidence: analysis of data obtained by a media surveillance system used to analyse public concerns about vaccines.
abstract: BACKGROUND
  The intensity, spread, and effects of public opinion about vaccines are growing as new modes of communication speed up information sharing, contributing to vaccine hesitancy, refusals, and disease outbreaks. We aimed to develop a new application of existing surveillance systems to detect and characterise early signs of vaccine issues. We also aimed to develop a typology of concerns and a way to assess the priority of each concern.
  
  
  METHODS
  Following preliminary research by The Vaccine Confidence Project, media reports (eg, online articles, blogs, government reports) were obtained using the HealthMap automated data collection system, adapted to monitor online reports about vaccines, vaccination programmes, and vaccine-preventable diseases. Any reports that did not meet the inclusion criteria--any reference to a human vaccine or vaccination campaign or programme that was accessible online--were removed from analysis. Reports were manually analysed for content and categorised by concerns, vaccine, disease, location, and source of report, and overall positive or negative sentiment towards vaccines. They were then given a priority level depending on the seriousness of the reported event and time of event occurrence. We used descriptive statistics to analyse the data collected during a period of 1 year, after refinements to the search terms and processes had been made.
  
  
  RESULTS
  We analysed data from 10,380 reports (from 144 countries) obtained between May 1, 2011, and April 30, 2012. 7171 (69%) contained positive or neutral content and 3209 (31%) contained negative content. Of the negative reports, 1977 (24%) were associated with impacts on vaccine programmes and disease outbreaks; 1726 (21%) with beliefs, awareness, and perceptions; 1371 (16%) with vaccine safety; and 1336 (16%) with vaccine delivery programmes. We were able to disaggregate the data by country and vaccine type, and monitor evolution of events over time and location in specific regions where vaccine concerns were high.
  
  
  CONCLUSIONS
  Real-time monitoring and analysis of vaccine concerns over time and location could help immunisation programmes to tailor more effective and timely strategies to address specific public concerns.
  
  
  BACKGROUND
  Bill & Melinda Gates Foundation.
authors.affiliation: London School of Hygiene & Tropical Medicine, London, UK; Chatham House Centre for Global Health Security, Royal Institute of International Affairs, London, UK. Electronic address: heidi.larson@lshtm.ac.uk.
authors.forename: Heidi J
authors.initials: HJ
authors.lastname: Larson
authors.affiliation: London School of Hygiene & Tropical Medicine, London, UK.
authors.forename: David Md
authors.initials: DM
authors.lastname: Smith
authors.affiliation: London School of Hygiene & Tropical Medicine, London, UK.
authors.forename: Pauline
authors.initials: P
authors.lastname: Paterson
authors.affiliation: ProMED-mail, International Society for Infectious Diseases, Brookline, MA, USA.
authors.forename: Melissa
authors.initials: M
authors.lastname: Cumming
authors.affiliation: London School of Hygiene & Tropical Medicine, London, UK.
authors.forename: Elisabeth
authors.initials: E
authors.lastname: Eckersberger
authors.affiliation: HealthMap, Boston Children's Hospital Informatics Program, and Division of Emergency Medicine, Boston Children's Hospital, Boston, MA, USA; Department of Biomedical Engineering, Boston University, Boston, MA, USA.
authors.forename: Clark C
authors.initials: CC
authors.lastname: Freifeld
authors.affiliation: London School of Hygiene & Tropical Medicine, London, UK.
authors.forename: Isaac
authors.initials: I
authors.lastname: Ghinai
authors.affiliation: London School of Hygiene & Tropical Medicine, London, UK.
authors.forename: Caitlin
authors.initials: C
authors.lastname: Jarrett
authors.affiliation: ProMED-mail, International Society for Infectious Diseases, Brookline, MA, USA.
authors.forename: Louisa
authors.initials: L
authors.lastname: Paushter
authors.affiliation: HealthMap, Boston Children's Hospital Informatics Program, and Division of Emergency Medicine, Boston Children's Hospital, Boston, MA, USA; Department of Paediatrics, Harvard Medical School, Boston, MA, USA.
authors.forename: John S
authors.initials: JS
authors.lastname: Brownstein
authors.affiliation: ProMED-mail, International Society for Infectious Diseases, Brookline, MA, USA; University of Massachusetts Medical School, Worcester, MA, USA.
authors.forename: Lawrence C
authors.initials: LC
authors.lastname: Madoff
mesh_terms: D003141:Communicable Diseases / Q000453:epidemiology; D003199:Computer Systems; D003625:Data Collection / Q000379:methods; D004812:Epidemiologic Methods; D006801:Humans; D010342:Patient Acceptance of Health Care; D011639:Public Opinion; D014611:Vaccination / Q000009:adverse effects / Q000379:methods* / Q000523:psychology*; D014612:Vaccines / Q000008:administration & dosage* / Q000009:adverse effects / Q000276:immunology
chemical_list: D014612:Vaccines