According to the results of a new study that was just made available online by the Journal of the American Medical Association (JAMA), people who plan to take Tamiflu to prevent catching the flu, or to limit symptoms and the duration of the illness if they have already become infected with the flu, should probably make other plans. According to the results of this study, there are now flu strains resistant to Tamiflu.

The strain of flu that is circulating in the U.S. that is showing resistance to Tamiflu is the H1N1 strain. According to the Atlanta-based U.S. Centers for Disease Control and Prevention (CDC), this is the most common type of flu this year.

Last year, Tamiflu resistance was found in only 12 percent of the strains circulating. This year, 98.5% of H1N1 flu strains are resistant to Tamiflu. Terence Hurley, a spokesman for Roche who manufacturers Tamiflu, emailed a statement which emphasized the fact that flu viruses constantly mutate while the types of strains circulating among the population change as well.

According to the CDC's Alicia Fry, head researcher for the above-referenced study, the use of Tamiflu itself has not led to the development of these resistant strains. The Tamiflu resistance researchers discovered is not the same as bacterial resistance to antibiotics which develops through misuse or overuse. The ability of flu viruses to mutate is why a new vaccine must be developed each year.

According to the World Health Organization, between 5 and 15 percent of the world's population comes down with the flu each year. Between 250,000 and 500,000 people die from the flu each year. According to Fry, “The vaccine is still the best form of prevention. We also know that these strains [resistant to Tamiflu] are susceptible to other antiviral drugs.”

The strains resistant to Tamiflu do not show any resistance to Relenza (made by GlaxoSmithKline). The CDC is recommending that people who are suffering from the flu take Relenza or generic rimantadine along with Tamiflu.

According to the CDC, November through March is prime flu season in the U.S. According to Fry, this year's flu vaccine is a good match to the strains that are circulating. The flu vaccine is developed anew each year to provide protection for the upcoming flu season.