An at-home treatment for COVID-19 that can prevent serious illness was authorized by the Food and Drug Administration on Wednesday, offering a note of optimism for the future of the pandemic as the world faces the omicron variant.
When taken early, Pfizer's pill was 89% effective at reducing the risk of severe illness and death from COVID-19, according to the company, and was effective against omicron.
Pfizer CEO Albert Bourla estimated that 1,200 deaths and 6,000 hospitalizations would be prevented for every 100,000 COVID-19 patients who take the pills.
The FDA said the pill, Paxlovid, was authorized for the treatment of mild-to-moderate coronavirus disease in anyone 12 years and older who weighs at least about 88 pounds. Patients must test positive and be at high risk for progression to severe COVID-19, including hospitalization or death.
Paxlovid will be available by prescription only and should be started as soon as possible, ideally within five days of symptom onset, the FDA said.
"This authorization provides a new tool to combat COVID-19 at a crucial time in the pandemic as new variants emerge and promises to make antiviral treatment more accessible to patients who are at high risk for progression to severe COVID-19," Dr. Patrizia Cavazzoni, director of the FDA's Center for Drug Evaluation and Research, said in a press release.
The treatment course requires taking several pills, twice per day, for five days.
Tens of thousands of courses of the medication will be available this month, and by January that number will grow to the hundreds of thousands. Within the first quarter of 2022, Pfizer expects to be producing millions a month.
The U.S. government has already contracted with Pfizer to purchase at least 10 million courses by the end of next year at $530 a course.
There is not expected to be any direct cost to patients.
But supply is expected to be limited for months as production ramps up and cases surge worldwide over the winter, already leading to concerns about equitable distribution.
Still, the pills offer hope, particularly as the omicron variant spreads rapidly across the U.S.
Vaccination and booster shots are the best defense against omicron, offering up to 80% protection by some estimates, and unvaccinated Americans will be hit hardest by the surge. But there will also be more breakthrough infections among vaccinated people because of omicron's mutations.
"While not a replacement for vaccines, the emergence of new variants has highlighted the need for new therapeutic lines of defense," said Dr. John Brownstein, an epidemiologist at Boston Children's Hospital and ABC News contributor.
"The combination of low friction access and high efficacy means that we finally have a therapy that can make a real impact on the trajectory of this pandemic," he said.
Public health experts and the pharmaceutical companies who make the pills also have been firm that the treatments alleviate illness -- they do not prevent it. Vaccines do, and they’re still the safest, most effective option to stay out of the hospital.
"I want to emphasize that no one should use the existence of the pill as an excuse to avoid vaccination," Bourla, Pfizer’s CEO, said.
The U.S. will also likely face some hurdles in the initial rollout -- another reason they shouldn’t be relied upon as an alternative to vaccination.
One concern is that the pills need to be taken early, which means patients will need a positive test and a doctor’s appointment very soon after they get sick. Testing delays and overburdened hospital systems could make that more challenging.
They are most effective "before a person becomes critically ill," said Dr. Paul Currier, director of the Respiratory Acute Care Unit at Massachusetts General Hospital. "Once a patient becomes critically ill, the virus has already caused a lot of inflammation in the body that likely cannot be stopped by medicines that only target the virus itself."
But pharmaceutical executives are optimistic that the pills will make a significant dent in the pandemic.
Pfizer's pill has the "potential to save the lives of patients around the world," Bourla said.
ABC News’ Dr. Navjot Kaur Sobti contributed to this report.