BioNTech and Pfizer have said a three-shot course of their Covid-19 vaccine was able to neutralise the new Omicron variant in a laboratory test.
The companies added that they could deliver an Omicron-based vaccine in March 2022 if needed.
The news came in the first official statement from vaccine manufacturers on the likely efficacy of their shot against Omicron.
BioNTech and Pfizer said that two vaccine doses resulted in significantly lower neutralising antibodies, but that a third dose of their vaccine increased the neutralising antibodies by a factor of 25.
Blood obtained from people that had their third booster shot a month ago neutralised the Omicron variant about as effectively as blood after two doses fought off the original virus.
"Ensuring as many people as possible are fully vaccinated with the first two dose series and a booster remains the best course of action to prevent the spread of Covid-19," Pfizer boss Albert Bourla said in the statement.
Though the necessity remains unclear, the companies said they would continue their effort to bring an Omicron-specific Covid-19 vaccine to market, which they kick-started when the new lineage first raised global concern among scientists on 25 November.
A planned output of 4 billion doses of the Comirnaty vaccine in 2022 was not expected to change if an adapted vaccine was required, they added.
The findings are broadly in line with a preliminary study published by researchers at the Africa Health Research Institute in South Africa on Tuesday.
It said that Omicron can partially evade protection from two doses of the Pfizer/BioNTech vaccine, suggesting also that a third shot might help fend off infection.
A lab analysis at the university hospital of Frankfurt, Germany, however found a reduced antibody response to Omicron even after three shots.
The US-German vaccine partners also struck an optimistic tone on the prospect of their shot protecting against any severe disease from Omicron, even though the lab data did not yield new insights on that.
The vast majority of surface structures on the Omicron spike protein targeted by the T-cells, which typically emerge after vaccination, are not affected by Omicron's mutations, they said.
"The companies believe that vaccinated individuals may still be protected against severe forms of the disease," they added.
T-cells are the second pillar of an immune response, alongside antibodies, and are believed to prevent severe disease by attacking infected human cells.