Influenza vaccinations offer greater protection for the appropriate populations because they offer coverage for influenza A and B. Influenza vaccine provides reasonable protection against immunized strains. The vaccination becomes effective 10-14 days after administration. Specific recommendations for individuals who should be immunized can be obtained from the CDC, which publishes regular updates of this information (see Seasonal Influenza Vaccination Resources for Health Professionals).
Influenza A viruses, including the 2 subtypes H1N1 and H3N2, and influenza B viruses currently circulate worldwide, but the prevalence of each can vary among communities and within a single community over the course of an influenza season.
In the 2009-2010 flu season, approximately 99% of typed influenza viruses were H1N1. In the United States, 4 prescription antiviral medications (ie, oseltamivir, zanamivir, amantadine, rimantadine) are approved for treatment and chemoprophylaxis of influenza.
The vast majority of the 2009-2010 influenza was susceptible to oseltamivir and zanamivir but resistant to the adamantanes (amantadine, rimantadine). In addition, the FDA issued an emergency use authorization for a third neuraminidase inhibitor, peramivir, for the treatment of hospitalized patients with H1N1 influenza who have potentially life-threatening suspected or laboratory-confirmed infection. Peramivir IV is available through the CDC upon request of a licensed physician.
Complete recommendations are available in a CDC Health Advisory.
Zanamivir is an inhibitor of neuraminidase, which is a glycoprotein on the surface of the influenza virus that destroys the infected cell's receptor for viral hemagglutinin. By inhibiting viral neuraminidase, release of viruses from infected cells and viral spread are decreased. It is effective against both influenza A and B and is inhaled through Diskhaler oral inhalation device. Circular foil disks containing 5-mg blisters of drug are inserted into the supplied inhalation device.
Rimantadine inhibits viral replication of influenza A virus H1N1, H2N2, and H3N2 and prevents viral penetration into a host by inhibiting uncoating of influenza A. NOTE: Because of resistance, it is not recommended by the CDC as of the 2005-2006 influenza season. Laboratory testing by the CDC on the predominant strain of influenza (H3N2) currently circulating in the United States shows that it is resistant to these drugs.
Oseltamivir inhibits neuraminidase, which is a glycoprotein on the surface of influenza virus that destroys an infected cell's receptor for viral hemagglutinin. By inhibiting viral neuraminidase, this agent decreases release of viruses from infected cells and thus viral spread. It is effective in treating influenza A or B. Start within 40 hours of symptom onset. It is available as a capsule and oral suspension.
Peramivir elicits antiviral activity by inhibiting influenza virus neuraminidase, an enzyme that releases viral particles from the plasma membrane of infected cells. It is indicated for treatment of acute uncomplicated influenza in patients aged 6 months and older who have been symptomatic for less than 2 days.