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Weekly UpdatesATLANTA -- The Centers for Disease Control and Prevention's vaccine advisory panel voted to update its guidelines on antiviral treatment of influenza to include new information about antiviral resistance of seasonal influenza and address influenza caused by the pandemic strain of H1N1.
At the time of the Advisory Committee on Immunization Practice's June meeting, all pandemic H1N1 viruses tested were sensitive to oseltamivir and zanamivir and resistant to adamantadines. In contrast, seasonal H1N1 influenza is resistant to oseltamivir but susceptible to the other two antivirals. As of now, all circulating seasonal influenza H3N2 and B strains are susceptible to zanamivir, Dr. Anthony J. Fiore of the CDC's influenza division said at the meeting.
Subsequent to the meeting, a patient with oseltamivir-resisrant novel H1N1 was identified in Denmark. This does not change the recommendations the committee voted on, CDC spokesman Tom Skinner said in an interview.
Antiviral treatment should be started as soon as possible after illness onset. Persons for whom antiviral treatment should be considered include those with influenza viral pneumonia or influenza and complicating bacterial pneumonia. The treatment also should be considered for patients hospitalized with influenza and those at higher risk for influenza complications, regardless of illness severity.
Zanamivir is recommended if laboratory testing is not done or is negative but there is clinical suspicion of influenza. The antiviral also is recommended if a patient tests positive for influenza A, influenza A and B, or seasonal A(H1N1).
Combined treatment with oseltamivir plus rimantadine is an acceptable alternative if zanamivir is unavailable or can't be tolerated.
Either oseltamivir or zanamivir is recommended for positive A(H3N2), novel A(H1N1), or B strains.
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Other information providers should consider:
* Recommended neuraminidase inhibitors are not licensed for chemoprophylaxis of children aged less than 1 year (oseltamivir) or aged less than years (zanamivir).
* A recent Emergency Use Authorization provides information on the use of oseltamivir for children aged less than 1 year.
* Some experts prefer weight-based dosing for children aged less than 1 year, particularly for very young or premature infants.
* When weight-based dosing is used for chemoprophylaxis in infants aged less than 1 year, those 6 months or older should receive 3.5 mg/kg per dose twice daily, and those aged less than 6 months should receive 3.0 mg/kg per dose twice daily.
Rather than voting simultaneously on recommendations for chemoprophylaxis, ACIP decided instead to include a short paragraph within the treatment guidelines about chemoprophylaxis that will include the address for the CDC's H1N1 Web page (www.cdc.gov/H1N1). Information on that site is updated frequently, and the need for chemoprophylaxis is expected to change as more becomes known about transmission of the novel H1N1 virus and vaccine availability, ACIP member Dr. Kathleen Neuzil said in an interview.
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