title: A case-control study of influenza vaccine effectiveness among Malaysian pilgrims attending the Haj in Saudi Arabia.
abstract: OBJECTIVE
  To determine influenza vaccine effectiveness against clinically defined influenza-like illness among Malaysian pilgrims attending the Haj in Saudi Arabia.
  
  
  METHODS
  During February and March 2000, the authors conducted an unmatched case-control study. Case patients were identified at one of five hotel clinics, while controls were residents of these hotels who had not attended a clinic.
  
  
  RESULTS
  Among 820 case patients--84% of whom had received antibiotics--and 600 controls, the adjusted vaccine effectiveness against clinic visits for influenza-like illness was 77% (95% confidence interval: 69, 83), and that against receipt of antibiotics was 66% (95% confidence interval, 54, 75). The vaccine did not prevent clinic visits for non-influenza-like upper respiratory tract illness (adjusted vaccine effectiveness, 20%; 95% confidence interval: -24, 49).
  
  
  CONCLUSIONS
  Influenza vaccine was effective in preventing clinic visits for influenza-like illness and antibiotic use. Pilgrims traveling to the Haj in Saudi Arabia should consider influenza vaccination use.
authors.affiliation: Institute for Medical Research, Kuala Lumpur, Malaysia.
authors.forename: Amal Nasir
authors.initials: AN
authors.lastname: Mustafa
authors.forename: Bradford D
authors.initials: BD
authors.lastname: Gessner
authors.forename: Raman
authors.initials: R
authors.lastname: Ismail
authors.forename: Ahmad Faudzi
authors.initials: AF
authors.lastname: Yusoff
authors.forename: Nasuruddin
authors.initials: N
authors.lastname: Abdullah
authors.forename: Ilina
authors.initials: I
authors.lastname: Ishak
authors.forename: Norazmi
authors.initials: N
authors.lastname: Abdullah
authors.forename: Mohd Ismail
authors.initials: MI
authors.lastname: Merican
mesh_terms: D016022:Case-Control Studies; D005260:Female; D006801:Humans; D009980:Influenza A virus / Q000276:immunology; D009981:Influenza B virus / Q000276:immunology; D007252:Influenza Vaccines / Q000008:administration & dosage / Q000276:immunology*; D007251:Influenza, Human / Q000517:prevention & control* / Q000821:virology; D007514:Islam; D008296:Malaysia; D008297:Male; D008875:Middle Aged; D012529:Saudi Arabia; D014195:Travel; D014611:Vaccination
chemical_list: D007252:Influenza Vaccines