Every flu season, the same questions come up in doctors' offices, pharmacies and family discussions: Do antiviral drugs really help? Are they worth the side effects? And how do you know if you need one?
Those questions matter more than ever. Online misinformation has made some people suspicious of prescription drugs, while others assume antivirals are miracle cures. Here's the practical, "news you can use" version — what flu antivirals can and can't do, who should take them, and how to decide quickly if they're right for you.
I've had a long professional relationship with the flu virus. As a graduate student, I helped discover one of the key enzymes the virus uses to reproduce. At the time, it was basic science — trying to understand how an important virus works. Decades later, that research helped lead to drugs that can interrupt the virus's life cycle. Even with that background, I'm the first to say that antivirals are only helpful tools, not magic bullets.
Today, there are four FDA-approved antiviral medications for influenza, all available by prescription. In everyday outpatient care, however, most doctors choose between two: Tamiflu (oseltamivir) and Xofluza (baloxavir). The others have limitations. Relenza is inhaled and isn't safe for people with asthma or chronic lung disease. Rapivab must be given intravenously and is usually reserved for hospitalized patients.
So what can flu antivirals actually do? When started early, they have been shown to:
—Shorten the duration of illness by about one to two days in most people, and sometimes more in young children.
—Reduce the severity of symptoms — fewer fevers and body aches, and less misery overall.
—Lower the risk of complications, such as ear infections in children and pneumonia in adults.
—Reduce the risk of death in high-risk patients, particularly older adults and those hospitalized.
—Prevent flu after exposure to someone known to have the flu, such as a household member.
What they don't do is instantly cure the flu. They don't make symptoms disappear overnight, and they don't replace rest, fluids and common-sense care. Timing is crucial. These drugs work best when started within 48 hours of symptom onset. Waiting several days to "see how bad it gets" is precisely the wrong approach for people at higher risk.
Even 48 hours after the onset of symptoms, antivirals may still help people who are very sick or have serious risk factors, but earlier is always better.
Before asking for treatment, it's important to answer a basic question: Do you actually have the flu? Influenza usually hits suddenly, with high fever, intense fatigue, headaches and body aches. Colds tend to come on more gradually. COVID-19 can look very similar to the flu, but the treatments are different. Many home tests now check for both viruses at once, which can help guide the next step.
Most people tolerate flu antivirals well. The most common side effects — especially with Tamiflu — are nausea and vomiting, which often improve if the medication is taken with food. Headaches can occur. Serious side effects are rare, and most patients complete treatment without problems. For those who need them, the benefits of the drugs clearly outweigh the temporary downsides.
Not everyone with the flu needs an antiviral. Healthy adults and older children usually recover with rest, fluids and fever reducers alone. Certain groups are much more likely to benefit. Medical organizations such as the American Academy of Pediatrics and the Infectious Diseases Society of America recommend antiviral treatment for:
—Anyone hospitalized with flu.
—Anyone with severe or rapidly worsening illness.
—Children under 5 (especially under 2).
—Adults 65 and older.
—Pregnant women.
—People with weakened immune systems.
—People with chronic conditions such as heart disease, lung disease or diabetes.
If you fall into one of these categories, don't delay. Call your healthcare provider or use a test-to-treat service that can prescribe medication quickly.
The bottom line is simple: Flu antivirals are a proven intervention that works best when started early and used by people who stand to benefit the most. And it is important to remember that they are a backup, not a substitute, for prevention. Vaccination remains the single most effective way to prevent infection and to reduce the likelihood of severe illness, hospitalization and death from influenza.
If flu does break through, the best antiviral is the one you can obtain and start promptly.
Henry I. Miller, a physician and molecular biologist, is the Glenn Swogger Distinguished Scholar at the Science Literacy Project. He was the founding director of the FDA's Office of Biotechnology.