A box of new flu drug Xofluza.

A brand-new drug to shorten the duration of the flu—baloxavir marboxil (Xofluza)—just received approval from the Food and Drug Administration.

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“With thousands of people getting the flu every year, and many people becoming seriously ill, having safe and effective treatment alternatives is critical,” FDA Commissioner Scott Gottlieb, M.D., said in a statement. “This novel drug provides an important, additional treatment option.”

The drug should be available for purchase within the next few weeks, in time for most of the flu season, according to a spokesman for Genentech, the company that distributes Xofluza in the U.S.

As flu season ramps up, here are answers to several key questions you might be asking about this new drug.

How Well Does It Work?

The data from clinical trials suggest that Xofluza, approved for most healthy people over age 12, works about as well as oseltamivir (Tamiflu and generic)—the most commonly used flu treatment currently available—at reducing the length of a flu illness. Overall, both appear to cut the time people have flu symptoms from a little over three days to a little over two days.

What’s Different About Xofluza?

Similar to Tamiflu, it needs to be taken within 48 hours of developing symptoms to be effective. And for Xofluza, the sooner the better: In one clinical trial, published in September in the New England Journal of Medicine (NEJM), people who took the drug within 24 hours of getting sick had symptoms for less time than those who took it between 24 and 48 hours after developing flu symptoms.

Side effects appear to be similar to those of Tamiflu. In the NEJM study, about 20 percent of participants who received Xofluza experienced some mild side effects, including diarrhea, bronchitis, nausea, and sinusitis. The rates of these side effects were about the same for study subjects who received either Tamiflu or a placebo.

However, Xofluza requires only one dose. (The size of the dose depends on your weight.) A course of Tamiflu entails multiple doses over several days.

And preliminary evidence suggests that Xofluza might be effective against strains of flu that have developed resistance to Tamiflu, though this has yet to be confirmed in clinical studies.

While Xofluza is approved only for healthy people 12 and older, Tamiflu can be used in children as young as two weeks. Tamiflu is also approved for pregnant women: Currently, Genentech advises women to let their doctor know if they are pregnant, planning to become pregnant, or breastfeeding—before using Xofluza.

And unlike Tamiflu, Xofluza should be taken only by people with an “uncomplicated” flu bug, meaning it’s not for those who have become seriously ill from the viral infection. Clinical trial data didn’t show how well the drug would work for people who are hospitalized from flu, for instance.

How Much Will It Cost?

According to Genentech, Xofluza’s retail price will be $150. But the company is providing coupons to reduce the cost of the drug, available here. If your health insurer covers the drug, the coupon could reduce your cost to as little as $30; otherwise, the coupon could cut your out-of-pocket price to $90.

Do I Still Need a Flu Shot?

Yes. Preventing the flu altogether is always preferable to catching the bug and treating it with an antiviral, according to the FDA. Although the flu vaccine isn’t perfect, it’s the most effective step you can take to keep yourself healthy this winter.

And you should get the vaccine as soon as you can—it takes about two weeks for the shot’s protection to take full effect.

Editor's Note: This story has been corrected; it originally misstated the estimated price of Xofluza with a manufacturer's coupon for people without insurance.