Effectiveness of oseltamivir in preventing influenza in household contacts: a randomized controlled trial.
BACKGROUND
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).


METHODS
Randomized, double-blind, placebo-controlled study conducted at 76 centers in North America and Europe during the winter of 1998-1999.


METHODS
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).


METHODS
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 treatment.


METHODS
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.


CONCLUSIONS
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.
Welliver
R
R
The Medical Building, 327 Mile End Rd, London, England E1 4NS. j.s.oxford@retroscreen.com
Monto
A S
AS
Carewicz
O
O
Schatteman
E
E
Hassman
M
M
Hedrick
J
J
Jackson
H C
HC
Huson
L
L
Ward
P
P
Oxford
J S
JS
D000081:Acetamides / Q000627:therapeutic use*; D000293:Adolescent; D000328:Adult; D000368:Aged; D000998:Antiviral Agents / Q000627:therapeutic use*; D004311:Double-Blind Method; D004791:Enzyme Inhibitors / Q000627:therapeutic use*; D005191:Family Characteristics; D005260:Female; D006801:Humans; D007251:Influenza, Human / Q000175:diagnosis / Q000517:prevention & control*; D008297:Male; D008875:Middle Aged; D009439:Neuraminidase / Q000037:antagonists & inhibitors*; D009666:Nose / Q000821:virology; D009975:Orthomyxoviridae / Q000302:isolation & purification; D053139:Oseltamivir; D010614:Pharynx / Q000821:virology; D017201:Virus Shedding
D000081:Acetamides; D000998:Antiviral Agents; D004791:Enzyme Inhibitors; D053139:Oseltamivir; D009439:Neuraminidase