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Welliver R, Monto AS, Carewicz O, et al. Effectiveness of Oseltamivir in Preventing Influenza in Household Contacts: A Randomized Controlled Trial. JAMA. 2001;285(6):748–754. doi:10.1001/jama.285.6.748
Author Affiliations: Children's Hospital, Buffalo, NY (Dr Welliver); University of Michigan School of Public Health, Ann Arbor (Dr Monto); Comprehensive Clinical Research, Berlin, NJ (Dr Hassman); Kentucky Pediatric and Adult Research, Bardstown, Ky (Dr Hedrick); Roche Global Development, Welwyn, England (Drs Jackson, Huson, and Ward); and St Bartholomew's and Royal London Hospital School of Medicine and Dentistry, and Retroscreen Virology Ltd, London, England (Dr Oxford). Dr Carewicz is in private practice in Heidelberg, Germany, and Dr Schatteman is in private practice in Drogen, Ghent, Belgium.
Context Influenza virus is easily spread among the household contacts of an
infected person, and prevention of influenza in household contacts can control
spread of influenza in the community.
Objective To investigate the efficacy of oseltamivir in preventing spread of influenza
to household contacts of influenza-infected index cases (ICs).
Design and Setting Randomized, double-blind, placebo-controlled study conducted at 76 centers
in North America and Europe during the winter of 1998-1999.
Participants Three hundred seventy-seven ICs, 163 (43%) of whom had laboratory-confirmed
influenza infection, and 955 household contacts (aged ≥12 years) of all
ICs (415 contacts of influenza-positive ICs).
Interventions Household contacts were randomly assigned by household cluster to take
75 mg of oseltamivir (n = 493) or placebo (n = 462) once daily for 7 days
within 48 hours of symptom onset in the IC. The ICs did not receive antiviral
Main Outcome Measure Clinical influenza in contacts of influenza-positive ICs, confirmed
in a laboratory by detection of virus shedding in nose and throat swabs or
a 4-fold or greater increase in influenza-specific serum antibody titer between
baseline and convalescent serum samples.
Results In contacts of an influenza-positive IC, the overall protective efficacy
of oseltamivir against clinical influenza was 89% for individuals (95% confidence
interval [CI], 67%-97%; P<.001) and 84% for households
(95% CI, 49%-95%; P<.001). In contacts of all
ICs, oseltamivir also significantly reduced incidence of clinical influenza,
with 89% protective efficacy (95% CI, 71%-96%; P<.001).
Viral shedding was inhibited in contacts taking oseltamivir, with 84% protective
efficacy (95% CI, 57%-95%; P<.001). All virus
isolates from oseltamivir recipients retained sensitivity to the active metabolite.
Oseltamivir was well tolerated; gastrointestinal tract effects were reported
with similar frequency in oseltamivir (9.3%) and placebo (7.2%) recipients.
Conclusion In our sample, postexposure prophylaxis with oseltamivir, 75 mg once
daily for 7 days, protected close contacts of influenza-infected persons against
influenza illness, prevented outbreaks within households, and was well tolerated.
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