Pfizer said on Friday that its experimental, easy-to-use antiviral pill for COVID-19 cut rates of hospitalisation and death by nearly 90 per cent in high-risk adults.

Currently all COVID-19 treatments require an IV or injection, except for in the United Kingdom where Merck’s COVID-19 pill was approved for use on Thursday. The UK became the first country in the world to give it authorisation.

Pfizer said it will ask the Food and Drug Administration (FDA) in the United States and international regulators to authorise its pill as soon as possible, after independent experts recommended halting the company’s study based on the strength of its results.

"We were hoping that we had something extraordinary, but it’s rare that you see great drugs come through with almost 90 per cent efficacy and 100 per cent protection for death,” said Dr. Mikael Dolsten, Pfizer’s chief scientific officer, in an interview.

Researchers worldwide have been racing to find a COVID-19 pill that can be taken at home to ease symptoms, speed-up recovery and reduce the burden on hospitals and doctors.

What did the results show?

Pfizer released the preliminary results of its study, which surveyed 775 adults on Friday.

Results showed patients taking the company's drug along with another antiviral had an 89 per cent reduction in their combined rate of hospitalisation or death after a month, compared to patients taking a placebo.

Fewer than 1 per cent of patients taking the drug needed to be hospitalised and no one died. In the comparison group, 7 per cent were hospitalised and there were seven deaths.

Study participants were unvaccinated, with mild-to-moderate COVID-19, and were considered high risk for hospitalisation due to health problems like obesity, diabetes or heart disease. Treatment began within three to five days of initial symptoms, and lasted for five days.

Pfizer reported few details on side effects but said rates of problems were similar between the groups at about 20 per cent.

An independent group of medical experts monitoring the trial recommended stopping it early, standard procedure when interim results show such a clear benefit.

The data has not yet been published for peer review, the normal process for vetting new medical research.

How does it work?

The European Medicine Agency said last week that it started a rolling review of the oral antiviral medicine molnupiravir, produced by Merck.

While pregnant women were excluded from the Merck trial due to a potential risk of birth defects, Pfizer’s drug did not have any similar restrictions.

The Merck drug works by interfering with the coronavirus' genetic code, a novel approach to disrupting the virus.

Pfizer’s drug is part of a decades-old family of antiviral drugs known as protease inhibitors, which revolutionised the treatment of HIV and hepatitis C. The drugs block a key enzyme which viruses need to multiply in the human body.

The drug, which has not yet been named, was first identified during the SARS outbreak originating in Asia during 2003.

Last year, company researchers decided to revive the medication and study it for COVID-19, given the similarities between the two coronaviruses.