NASHVILLE, Tenn. (WKRN) — President Joe Biden announced this week the federal government is doubling its original order of 10 million courses of the Pfizer COVID-19 antiviral pill. The two-drug regimen called “Paxlovid” works by inhibiting a protein in the COVID-19 virus to stop it from replicating.

“It’s designed to reduce the severity of the infection and keep you out of the hospital,” said Dr. William Schaffner, Professor of Medicine in the Division of Infectious Diseases at Vanderbilt University School of Medicine. 

Schaffner said he hopes this new treatment will reduce hospitalizations, a key factor in getting the pandemic under control. In a clinical trial, it was nearly 90% effective in preventing hospitalizations and deaths in patients more at risk for severe illness.

“This is directed at people who are at high risk of getting serious disease, people who are older over age 65, and if you’re younger and you have a whole series of underlying illnesses, and if you’re immune-compromised,” Dr. Schaffner said.

The qualifications are the same whether you’re vaccinated or not.

“That’s not the distinction,” Dr. Schaffner said. “The distinction is whether you have had a condition that predisposes you to serious underlying illness.”

Those at high risk, age 12 and older, should contact their doctor as soon as possible after getting a positive test. The regimen is by prescription only and is meant to be started within five days of symptom onset.

Possible side effects include impaired taste, diarrhea, high blood pressure and muscle aches.

“The doctor should screen you to make sure you don’t have underlying liver disease, because that can be a side effect that can activate that,” Dr. Schaffner said. “But my understanding is that this medication is pretty well tolerated.”

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Discuss other medications you take with your doctor and pharmacist because some could cause serious interactions with Paxlovid. Pfizer reportedly shipped the first round of treatments on Christmas Eve, but it will likely take months before the supply ramps up because the pills are complex to manufacture.