CDC warns severe flu season; urges Tamiflu, Relenza use
This article was originally published in Scrip
With a vaccine that has turned out to be a poor match for the strain that is predominant this season in the US – influenza A (H3N2) – and an anticipated bad year for the virus, the Centers for Disease Control and Prevention is urging doctors not to wait for test results if the disease is suspected before prescribing antivirals.
The two FDA-approved influenza antivirals are Roche’s and Genentech's Tamiflu (oseltamivir) and GlaxoSmithKline's Relenza (zanamivir), which have been shown to be effective in reducing severe outcomes of the flu, such as shortening the duration of fever and illness symptoms, reducing the risk of complications, like otitis media in young children and pneumonia requiring antibiotics in adults, and lowering the risk of death among hospitalized patients.
When H3 strains dominate, they tend to be associated with tougher seasons in general – resulting in more illnesses, hospitalizations and deaths, said CDC Director Dr Tom Frieden.
H3N2 viruses were predominant during the 2003-04, 2007-08 and 2012-13 seasons – the three seasons with the highest death levels in the past decade, the CDC said.
So with a vaccine that provides only 48% protection against H3N2, which has mutated since the strains were selected last winter for this season's shot and nasal spray, and a more severe influenza anticipated, Dr Frieden said antivirals are an "important second line of defense to treat the flu" (scripintelligence.com, 4 December 2014, 5 December 2014).
"This year, treatment with antiviral drugs is especially important, particularly for people who are at high risk of serious flu complications or for people who are very sick with flu," he said, noting the drugs should be taking within 48 hours of onset of the flu.
Although there's been some shortages of antivirals during some recent flu seasons, Dr Joseph Bresee, chief of the CDC's Influenza Epidemiology and Prevention Branch, insisted there would be enough Tamiflu and Relenza to go around for the 2014-15 season, despite the potential for greater demand in light of the lesser vaccine protection.
Based on Genentech's forecasts, spokeswoman Tara Iannuccillo said the company anticipates "having ample supply" of both Tamiflu oral suspension and capsules for this season.
"We have produced sufficient supply of all Tamiflu formulations for a severe flu season and are currently working with distributors and national retail pharmacies to provide consistent access to Tamiflu," she told Scrip.
Ms Iannuccillo acknowledged, however, that despite robust supply nationally, "from time-to-time, spot shortages may occur in local areas."
She said pharmacies should work with authorized distributors to obtain additional supply of Tamiflu capsules or oral suspension if needed.
"Flu activity is unpredictable and, as the manufacturer of Tamiflu, we do our best each season to anticipate flu spikes and work with our network of national distributors and pharmacies to provide Tamiflu to those areas of the country that need it most," Ms Iannuccillo said.
GSK spokesman Robert Perry said his company is "confident" there's sufficient quantity of Relenza available to fulfill any short-term needs and can manufacture additional product as needed.
Even with a sufficient supply of antivirals, Dr Frieden said the drugs are "greatly under-prescribed" in the US, "particularly for people who are at very high risk of getting the flu."
Fewer than one in six people who are severely ill with the flu get antivirals, Dr Frieden said.
"Antiviral drugs are even more important when circulating viruses are different from the vaccine virus," he said.
Dr Frieden disputed arguments that antivirals are not very effective.
He said the agency has reviewed the data specifically on Tamiflu and “it is the opinion of the CDC scientists that the evidence is strong.”
“It is not a miracle drug, but we believe it is an effective drug,” Dr Frieden said.