The first new influenza drug in 20 years was approved in October, and maker Genentech says Xofluza began reaching pharmacies recently — good timing for flu season.

With a single pill, Xofluza can shorten the fevers, chills, sore throat, and other symptoms that make a bout of the flu so miserable.

That’s not to suggest Xofluza is magical. It has limitations, just like Tamiflu, the well-known antiviral that has been around for 20 years. Experts still urge that you get the flu vaccine to reduce your chance of infection.

But as U.S. Food and Drug Administration Commissioner Scott Gott-lieb said in announcing its approval, Xofluza “provides an important, additional treatment option.”

Here are things to consider about that option — and the flu.

A MUTATING TARGET

Last flu season was the worst in decades, sickening 49 million people and killing 79,000. The dominant virus strain mutated and undercut the effectiveness of the vaccine, which is made each year to try to match circulating strains. On top of that, far fewer people got flu shots.

THE WINDOW OF OPPORTUNITY

Xofluza (baloxavir marboxil) works by preventing the virus from copying itself, while Tamiflu (oseltamivir phosphate) and two similar drugs keep the virus from spreading within the body. Either way, antivirals should be given within 48 hours of the first symptoms to be effective.

Ebbing Lautenbach, chief of infectious diseases at the University of Pennsylvania, said the flu usually hits hard and suddenly — unlike, say, a cold. “But it still requires a patient to feel lousy and then fairly quickly contact their provider,” he said. “If you’re outside the 48-hour window, there’s not much to be gained” from an antiviral.

SUFFERING LESS

Flu symptoms typically last from five to seven days. In the two clinical trials that led to approval, Xofluza provided relief more quickly than a placebo — by 26 hours. Xofluza and Tamiflu were similar in shortening suffering. As for side effects, Xofluza had no more than a placebo, while Tamiflu may sometimes cause nausea and vomiting.

SIMPLER TO USE

Xofluza is a single dose, unlike Tamiflu, which is taken twice a day for five days. In theory, Xofluza could reduce the problem of drug-resistant viruses emerging when patients don’t finish their antiviral prescription. But studies of Xofluza have shown that the virus may develop resistance after just one dose.

NOT FOR EVERYONE

Tamiflu is recommended for people at high risk of flu complications such as pneumonia, including children and older adults with chronic illnesses. Xofluza, in contrast, is currently approved for people 12 and older.

Genentech continues to study the pill with an eye toward expanded approval. It has already been shown to shorten the flu in people at high risk of complications.

COST

Xofluza costs $150, but Genentech offers coupons to cut the out-of-pocket cost for insured and uninsured patients. Tamiflu, which is made by Roche, the parent company of Genentech, also costs about $150. But generic oseltamivir is available for less than $50, according to GoodRX.