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This year’s flu outbreak is the worst it’s been in a decade, and the season’s not over. Over 12,000 people have already been hospitalized, so it’s safe to say many of us are willing to do anything to keep the virus at bay. One popular go-to remedy is Tamiflu. But does it actually help?

Tamiflu is a prescription antiviral medication used to minimize the symptoms of the flu. It works by attacking the flu virus early on to keep it from multiplying in your body. To be most effective, Tamiflu has to be taken within the first two days of the first signs of flu.

The FDA says that Tamiflu can also help prevent the flu, too, which is why it’s often prescribed to those who may have been contaminated by the flu virus through someone else but aren’t yet showing signs of symptoms.

So…does it work? On average, doctors say that it shortens the time you’re sick by about one day — if it’s taken within 48 hours of getting sick. Roche, the makers of Tamiflu, say that it can also reduce the number of patients who have serious complications from the flu.

Here’s where the controversy comes in.

The CDC recommends using Tamiflu to treat and prevent the flu, but as other outlets have pointed out, there doesn’t seem to be a ton of research to back that up. When The Atlantic asked the CDC for research that Tamiflu works, they said they rely more on “observational studies.” In 2009, an FDA spokesperson told the British Medical Journal that clinical trials “failed to demonstrate any significant difference in rates of hospitalization, complications, or mortality in patients receiving either Tamiflu or placebo.” And in 2014, research done by Cochrane Collaboration found similar results.

It’s also worth noting that Tamiflu itself can have some pretty nasty side effects, including nausea, vomiting, diarrhea, stomach pains, dizziness, and headaches. In a few cases it can even have severe side effects, especially on children, like seizures, self-injury, and hallucinations. One family in Indiana even believes that Tamiflu side effects are what led to the suicide of their 16-year-old son.

Despite all of this, people rely heavily on Tamiflu — there may even be a prescription shortage as the flu season progresses (if you’ve had the flu, you’ll know that the chance of shortening symptoms by even a single day is totally worth it).

And if you’re really concerned about the flu, the CDC maintains that the best method of defense is to get a flu shot. It’s not too late to get one if you haven’t already. And of course, talk to your doctor before taking any medication at all.

Be safe out there!