This file handout photo provided on November 16, 2021 by Pfizer shows the making of its experimental Covid-19 antiviral pills, Paxlovid, at its laboratory in Freiburg, Germany. AFP
The announcement came as a real-world study from South Africa showed two doses of the Pfizer-BioNTech vaccine was 70 percent effective in stopping severe illness from the new variant, a result called encouraging by researchers, though it represents a drop compared to earlier strains.
Data for the new pill, which hasn't yet been authorized anywhere in the world, came from more than 2,200 volunteers, and backed up preliminary findings announced last month.
The American drugmaker said its treatment, called Paxlovid, also held up against the Omicron variant in lab-testing.
Pfizer CEO Albert Bourla told CBS News the drug was a "game changer," and he expected the US Food and Drug Administration (FDA) to give its green light as soon as this month.
The trial showed that the pill reduced the need for hospitalization in high-risk adults with Covid-19 by 89 percent if the treatment was given within three days of symptom onset and by 88 percent if given within five days.
Overall, there were 12 deaths in the placebo group, and none in the drug group.
Side-effects were found at comparable rates between the treatment and placebo groups (23 percent and 24 percent, respectively), and were mostly mild.
Paxlovid also reduced the risk of severe disease, as well as the amount of virus detected, in a separate study of people at normal risk -- but the results were on the edge of statistical significance and need further confirmation.
New Type Of Drug
Paxlovid is a combination of two drugs -- nirmatrelvir, a new experimental medicine, and ritonavir, an existing antiviral used against HIV, both taken orally over five days.
Nirmatrelvir is known as a "protease inhibitor" and works by blocking the action of an enzyme the coronavirus needs to replicate. Ritonavir is administered to slow down the breakdown of nirmatrelvir inside the body.
Because Paxlovid does not target the fast-mutating spike proteins that stud the surface of the coronavirus, it should be more variant-proof than other treatments, such as synthetic antibody infusions, as well as antibodies evoked by most types of Covid vaccine.
Another Covid pill, Merck's molnupiravir, has already been authorized in Britain. A US panel of experts narrowly voted in favor of the Merck pill two weeks ago, but FDA authorization is still awaited.
Final study results showed molnupiravir reduced hospitalizations and deaths by a relatively disappointing 30 percent, and there were also safety concerns related to its mechanism of action, which differs from the Pfizer pill.
Merck itself recommended against molnupiravir's use in pregnant women after animal studies showed harm to fetuses.
Real-World Vaccine Data
The news comes as the heavily-mutated Omicron variant continues spreading fast around the world, raising alarms about surges in severe cases and deaths.
Even if early data suggesting that the variant is milder in most people is confirmed, its increased transmissibility and ability to overcome prior immunity may negate this advantage, by infecting higher numbers of people.
Many high-income countries have stepped up their campaigns to get people booster shots in order to restore vaccine efficacy.
The latest research out of South Africa found that two doses of the Pfizer-BioNTech vaccine still offered good protection against serious illness of 70 percent, though this was reduced from 93 percent during the country's Delta wave.
The study was based on the results of 78,000 PCR tests taken in South Africa between November 15 and December 7 and was conducted by Discovery along with the South African Medical Research Council (SAMRC).
It also found two doses were 33 percent effective against infection -- a result that lines up with early data from the UK Health Security Agency, which experts say underscores the case for a third dose.
The British research found a third dose of Pfizer -- either after two earlier doses of Pfizer or two of AstraZeneca -- brought efficacy against infection back up to 70-75 percent.
The South African research further confirmed reinfection risk is higher with Omicron, and a lower percentage of people infected with the new variant were hospitalized when compared to the country's first wave, after adjusting for vaccine status.
Very preliminary data suggests that children have a 20 percent higher risk of hospital admission with the new variant, but the absolute numbers remain very low.
"It is essential to recognize that these are incomplete and partial data," said Russell Viner, a professor of child and adolescent health at the University College London, though he also warned against complacency.