title: Systematic review: safety and efficacy of extended-duration antiviral chemoprophylaxis against pandemic and seasonal influenza.
abstract: BACKGROUND
  Neuraminidase inhibitors (NAIs) are stockpiled internationally for extended use in an influenza pandemic.
  
  
  OBJECTIVE
  To evaluate the safety and efficacy of extended-duration (>4 weeks) NAI chemoprophylaxis against influenza.
  
  
  METHODS
  Studies published in any language through 11 June 2009 identified by searching 10 electronic databases and 3 trial registries.
  
  
  METHODS
  Randomized, placebo-controlled, double-blind human trials of extended-duration NAI chemoprophylaxis that reported outcomes of laboratory-confirmed influenza or adverse events.
  
  
  METHODS
  2 reviewers independently assessed study quality and abstracted information from eligible studies.
  
  
  RESULTS
  Of 1876 potentially relevant citations, 7 trials involving 7021 unique participants met inclusion criteria. Data were pooled by using random-effects models. Chemoprophylaxis with NAIs decreased the frequency of symptomatic influenza (relative risk [RR], 0.26 [95% CI, 0.18 to 0.37]; risk difference [RD], -3.9 percentage points [CI, -5.8 to -1.9 percentage points]) but not asymptomatic influenza (RR, 1.03 [CI, 0.81 to 1.30]; RD, -0.4 percentage point [CI, -1.6 to 0.9 percentage point]). Adverse effects were not increased overall among NAI recipients (RR, 1.01 [CI, 0.94 to 1.08]; RD, 0.1 percentage point [CI, -0.2 to 0.4 percentage point]), but nausea and vomiting were more common among those who took oseltamivir (RR, 1.48 [CI, 1.86 to 2.33]; RD, 1.7 percentage points [CI, 0.6 to 2.9 percentage points]). Prevention of influenza did not statistically significantly differ between zanamivir and oseltamivir.
  
  
  CONCLUSIONS
  All trials were industry-sponsored. No study was powered to detect rare adverse events, and none included diverse racial groups, children, immunocompromised patients, or individuals who received live attenuated influenza virus vaccine.
  
  
  CONCLUSIONS
  Extended-duration zanamivir and oseltamivir chemoprophylaxis seems to be highly efficacious for preventing symptomatic influenza among immunocompetent white and Japanese adults. Extended-duration oseltamivir is associated with increased nausea and vomiting. Safety and efficacy in several subpopulations that might receive extended-duration influenza chemoprophylaxis are unknown.
authors: Stanford University Medical Center, Center for Health Policy and Center for Primary Care and Outcomes Research, Stanford Sleep Disorders Center, and Lane Medical Library, Stanford, California 94305, USA.
authors: Nayer
authors: N
authors: Khazeni
authors: Dena M
authors: DM
authors: Bravata
authors: Jon-Erik C
authors: JE
authors: Holty
authors: Timothy M
authors: TM
authors: Uyeki
authors: Christopher D
authors: CD
authors: Stave
authors: Michael K
authors: MK
authors: Gould
mesh_terms: D000998:Antiviral Agents / Q000008:administration & dosage* / Q000009:adverse effects; D004196:Disease Outbreaks / Q000517:prevention & control*; D004334:Drug Administration Schedule; D006801:Humans; D009980:Influenza A virus; D007251:Influenza, Human / Q000453:epidemiology / Q000517:prevention & control*; D009325:Nausea / Q000139:chemically induced; D009439:Neuraminidase / Q000037:antagonists & inhibitors*; D053139:Oseltamivir / Q000008:administration & dosage* / Q000009:adverse effects; D012307:Risk Factors; D014839:Vomiting / Q000139:chemically induced; D053243:Zanamivir / Q000008:administration & dosage* / Q000009:adverse effects
chemical_list: D000998:Antiviral Agents; D053139:Oseltamivir; D009439:Neuraminidase; D053243:Zanamivir