TAMIFLU® (oseltamivir phosphate) has been studied only in strains of influenza that were circulating at the time. The magnitude of effect of TAMIFLU in treating and preventing novel strains of influenza, such as those that may be involved in a pandemic, cannot be predicted.
What interventions might reduce the impact of a pandemic?
Overview
Researchers from the Los Alamos National Laboratory evaluated the effectiveness
of different intervention strategies for a flu pandemic by developing a model
that represents the US population and tests different properties of a potential
pandemic flu virus. They found that, depending on the contagiousness of the
virus, a variety of approaches could reduce the number of flu cases to fewer
than that of an annual flu season.
Mathematical modeling has significant limitations and these approaches cannot provide substantial evidence for effectivness claims.
Method
The scientists simulated a virtual outbreak on computers at the Los Alamos
National Laboratory. The researchers tested different interventions: distributing
antiviral treatments to infected individuals and others near them
to reduce symptoms and susceptibility; vaccinating people, possibly children
first, with either 1 or 2 shots of a vaccine not well matched to the strain
that may emerge; social distancing, such as restricting travel and
quarantining households; and closing schools.
No Interventions
The results showed that, with no intervention, a pandemic flu with low
contagiousness could peak after 117 days and infect about 33% of the US
population. A highly contagious virus could peak after 64 days and infect
about 54% of the population.
Using Interventions
The researchers then compared what might happen in scenarios involving the use
of different interventions.
When the simulated virus was less contagious, the 3 most effective single
measures included: distributing several million courses of antiviral treatment
to targeted groups 7 days after a pandemic alert; school
closures; and vaccinating 10 million people per week with 1 dose of a
poorly matched vaccine.
The results also showed that vaccinating school children first is more effective
than random vaccination when the vaccine supply is limited. Regardless of
contagiousness, social distancing measures, alone, had little effect.
But when the virus was highly contagious, all single-intervention strategies
left nearly half the population infected. In this instance, the only measures
that reduced the number of cases to below the annual flu rate involved a
combination of at least three different interventions, including a minimum of
182 million courses of antiviral treatment.
FOOTNOTE
16. National Institute of General Medical Sciences. National Institute of
Health. Computer model examines strategies to mitigate potential U.S.
flu pandemic (press release). Available at:
http://www.nigms.nih.gov/News/Results/FluModel040306. Accessed April 19, 2006
Indications
TAMIFLU is indicated for the treatment of uncomplicated influenza caused by viruses types A and B in patients 1 year and older who have been symptomatic for no more than 2 days.
TAMIFLU is also indicated for the prophylaxis of influenza in patients 1 year and older.
TAMIFLU is not a substitute for early and annual vaccination as recommended by the Centers for Disease Control's Advisory Committee on Immunization Practices (ACIP).
Prescribers should consider available information on influenza drug susceptibility patterns and treatment effects when deciding whether to use TAMIFLU.
Safety Information
There is no evidence for efficacy against any illness caused by agents other than influenza types A and B.
Treatment efficacy in subjects with chronic cardiac and/or respiratory disease has not been established. No difference in the incidence of complications was observed between the treatment and placebo groups in this population.
No information is available regarding treatment of influenza in patients at imminent risk of requiring hospitalization.
Efficacy of TAMIFLU has not been established in immunocompromised patients.
Safety and efficacy of repeated treatment or prophylaxis courses have not been studied.
Influenza can be associated with a variety of neurologic and behavioral symptoms, which can include events such as hallucinations, delirium and abnormal behavior, in some cases resulting in fatal outcomes. These events may occur in the setting of encephalitis or encephalopathy but can occur without obvious severe disease. There have been postmarketing reports (mostly from Japan) of delirium and abnormal behavior leading to injury, and in some cases resulting in fatal outcomes, in patients with influenza who were receiving TAMIFLU. Because these events were reported voluntarily during clinical practice, estimates of frequency cannot be made but they appear to be uncommon based on TAMIFLU usage data. These events were reported primarily among pediatric patients and often had an abrupt onset and rapid resolution. The contribution of TAMIFLU to these events has not been established. Patients with influenza should be closely monitored for signs of abnormal behavior. If neuropsychiatric symptoms occur, the risks and benefits of continuing treatment should be evaluated for each patient.
In postmarketing experience, rare cases of anaphylaxis and serious skin reactions, including toxic epidermal necrolysis, Stevens-Johnson syndrome and erythema multiforme, have been reported with TAMIFLU.
The most common adverse events reported >1% of patients treated with TAMIFLU and more commonly than in patients treated with placebo are:
Treatment of adult and pediatric patients - nausea, vomiting.
Prophylaxis of adult and pediatric patients - nausea, vomiting, abdominal pain.
Vaccination is considered the first line of defense against influenza.
