Why CDC Recommends Influenza Antiviral Drugs

The 2014-2015 flu season has been a difficult one for a number of reasons, including circulation of H3N2 viruses which are typically associated with more severe flu seasons, and reduced vaccine effectiveness because circulating H3N2 viruses are different or have “drifted” from the H3N2 virus used to make vaccine. A number of media and online outlets have inquired about the public health rationale behind CDC’s influenza antiviral recommendations. This statement provides background information and explains the rationale for CDC's influenza antiviral recommendations.
 

Getting a flu vaccine is the best way to prevent influenza illness and protect against its potentially deadly consequences. When a person is sick with flu, however, antiviral flu drugs are a treatment option. They work best when taken within 48 hours of becoming sick.

Two of the currently recommended flu antiviral drugs were first approved by the Food and Drug Administration (FDA) in 1999 to treat acute, uncomplicated influenza. The drugs work by binding to part of the flu virus -- the neuraminidase protein -- to stop replication of influenza viruses in the body[i]. Randomized control trial (RCT) data submitted to FDA by manufacturers showed these drugs reduced duration of illness and made symptoms milder[ii]^{,[iii],[iv],[v],[vi]}. No RCT data was submitted that looked at prevention of serious flu outcomes.

Since 1999 a large and growing body of observational data, including in hospitalized patients, shows there are benefits to using antiviral drugs beyond the treatment of uncomplicated illness. In medical practice, these drugs have been documented to reduce serious flu complications. In 2008, CDC began recommending these drugs for early treatment of severely ill and high risk patients based on that data. During and after the 2009 H1N1 pandemic, clinical studies in medical practices continued to show that people very ill with flu who got antiviral drugs fared better than those who did not; sometimes these drugs were associated with preventing severe illness and death [vii]^{,[viii],[ix],[x],[xi],[xii],[xiii],[xiv],[xv],[xvi],[xvii]}. For that reason, CDC continues to recommend that the neuraminidase inhibitor influenza antiviral drugs be used for early treatment of people who are very sick with influenza or of people who are sick who are at high risk of serious influenza-associated complications. Most previously healthy people will recover from flu without treatment.

CDC’s responsibility is to make public health recommendations using all available data. Its sister agency, FDA, evaluates new drugs for safety and efficacy—a very different and important role. The two agencies consider different data in carrying out their roles.  

CDC’s recommendations for using influenza antiviral medications aim to protect the people who are most vulnerable to serious complications from flu. The recommendations for antiviral drugs are based on data from randomized clinical trials as well as from observational studies of patients receiving treatment in medical practice.

CDC recognizes that currently recommended influenza antiviral drugs have limitations; however, these drugs are the only influenza-specific therapy approved by FDA with activity against circulating influenza viruses.

Severity indicators for the 2014-2015 season are among the highest seen in the past decade, including the highest hospitalization rate for people 65 and older in the 10 years since this type of record-keeping began.