Nobody knows for sure, claims the prestigious Cochrane Collaboration, a group that issues careful analyses of the evidence behind drugs and vaccines. Cochrane researchers say there's not enough evidence to prove Tamiflu works.
The CDC and the World Health Organization recommend the drug as effective. The FDA and the European Medicines Agency approve Tamiflu for the treatment and prevention of flu.
Tamiflu can lessen symptoms and make flu illness one to two days shorter, the CDC says. It can also help prevent flu illness in people who have come into close contact with a flu patient.
But it’s not a cure-all, says pediatric infectious disease specialist Marcelo Laufer, MD, of Miami Children's Hospital.
"One of the problems is that Tamiflu is seen by the public as a drug that will save you from all cases of the flu," he says. "Tamiflu can decrease the duration of illness by 30% to 40%, and decrease flu severity by about 40% -- but only if taken in the first 36 to 48 hours of illness. And you know that will not happen all the time."
Request for More Data
Cochrane researchers, joined by the BMJ (formerly the British Medical Journal), complained that Tamiflu maker Roche is keeping important data from the public. They note that despite requests dating back to 2009, Roche refuses to release crucial data from eight of 10 Tamiflu clinical trials.
"This means that taxpayers in the United Kingdom and around the world have spent billions of dollars stockpiling a drug for which no one except the manufacturer has seen the complete evidence base," Fiona Godlee, BMJ editor-in-chief, wrote in an editorial.
In a letter sent this week to respected Oxford professor John Bell -- a Roche board member -- Godlee warned that too much Tamiflu data is being kept secret.
"There are concerns on a number of fronts: the likely overstating of effectiveness and apparent under-reporting of potentially serious adverse effects," she wrote.
The data in question is what researchers call "patient-level data" collected from each study participant in a clinical trial, with only identifying information removed.
In a response to BMJ, Roche last month issued a statement saying it does not make the data available to protect patient confidentiality.
"Roche provided the Cochrane group with access to 3,200 pages of very detailed information, enabling their questions to be answered," the statement says.
What do doctors think about Tamiflu?
"Tamiflu, even in the best of circumstances, is of modest benefit," says Bruce Hirsch, MD, an infectious disease specialist at North Shore/Long Island Jewish Health System in Manhasset, N.Y. "And unless given within 48 hours of first symptoms, that modest benefit is lessened."
There's another approved flu drug -- Relenza -- but Hirsch says that in real-world practice, most doctors prescribe Tamiflu despite skepticism over its effectiveness.
"There is a lot of understanding [among doctors] of how limited the effect is," he says.