Health & Medical Cold,Fever,Flu,Cough

Why Antiviral Medications Are So Important When Flu Vaccines Don"t Work

Updated March 18, 2015.

Written or reviewed by a board-certified physician. See's Medical Review Board.

It is an unfortunate fact that some years the flu vaccine is less effective than others. Although researchers do their best to anticipate which strains of influenza will be circulating the following flu season, decisions must be made about which strains to include in the vaccine about 6 months in advance, essentially making it a guessing game. 

Influenza viruses mutate frequently and when this happens between flu seasons, it can mean the strains included in the vaccine are not the same as the strains that end up making a majority of people sick.


Flu vaccines contain 3 or 4 strains of the influenza virus - two strains of two different types of influenza A viruses and one or two strains of influenza B viruses. Most years there is a dominant influenza A strain that circulates early in the season and influenza B becomes more prevalent later in the season. 

When The Vaccine Isn't a Good Match

During years when the vaccine does not contain a good match to the predominant circulating strain of the flu, use of antiviral medications becomes more important than ever. 

If taken within 48 hours of the onset of flu symptoms, antiviral medications - such as Tamiflu, Relenza and Rapivab (IV) - can shorten the duration of the illness and lessen the severity of symptoms. For those who are at high risk for flu complications, taking Tamiflu if you have been or will be exposed to someone with the flu may reduce the chances that you will get it. 

Recent studies have even shown that people who are seriously ill with the flu and hospitalized can benefit from taking these antiviral medications.


There continues to be increasing evidence that these medications provide benefit for patients who are seriously ill or at high risk for complications and the CDC recommends that people who fall into these categories use them. Most otherwise healthy people without serious or complicated influenza infections will recover without treatment. 

If you fall into a high risk category and you get sick with the flu, contact your health care provider as soon as possible so you can get treatment.

What You Need to Know About Antivirals

Not everyone who gets the flu needs to take antiviral medications. They do have side effects and can be very expensive (depending on your insurance coverage). If you flu symptoms are not particularly severe and you are not at high risk for complications, you should recover from the flu in about a week without taking antiviral medications. 

People in high risk groups include:
  • Adults over age 65
  • Children under age 5 - even higher risk for those under age 2
  • Pregnant Women or those who have given birth in the past 2 weeks
  • Residents of Nursing Home or Long Term Care Facilities
  • American Indians and Alaskan Natives
  • People with chronic health conditions such as asthma, heart disease, HIV, neurological conditions and any other problem that affects the immune system 

If you are not sure if you fall into a high risk group for the flu, contact your health care provider to discuss your concerns. 

If you don't need antiviral treatment when you have the flu, there are still other flu treatment options that may help relieve your symptoms and make the illness more manageable until you recover.


"Why CDC Recommends Antiviral Drugs". CDC Newsroom 3 Mar 15. US Centers for Disease Control and Prevention. Department of Health and Human Services. 13 Mar 15. 

"People at High Risk of Developing Flu-Related Complications". Specific Groups. Seasonal Influenza (Flu) 8 Jan 15. US Centers for Disease Control and Prevention. Department of Health and Human Services. 13 Mar 15. 

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