Live updates: follow the latest news on Covid-19 variant Omicron
Vaccine maker Moderna could have a Covid-19 booster shot to tackle the Omicron variant tested and ready to file for US authorisation by March.
Boosters carrying genes specifically to combat mutations in the variant could be the quickest way to address any effect it may have on the potency of vaccines, Moderna president Stephen Hoge said.
"We've already started that programme," he said.
The company is also working on a multivalent vaccine that would include up to four different coronavirus variants, including Omicron.
That project could take several more months to complete, Mr Hoge said.
Omicron, which the World Health Organisation has called a "variant of concern", is being studied to determine whether it is more contagious or causes more severe illness than other variants.
Authorities are also working to find out whether it can evade current vaccines.
The US has detected its first case of the Omicron variant in California, the Centres for Disease Control and Prevention said on Wednesday.
Mr Hoge said prior guidance from the US Food and Drug Administration suggested the process to create a booster to tackle the strain could take three or four months.
"The Omicron-specific boosters, just realistically, are not before March and maybe more in the second quarter," he said.
Moderna will be able to manufacture the shot as it carries out testing, to allow it to have doses ready to distribute as soon as possible, he said.
Mr Hoge said the FDA was assessing the threat the variant poses to the protection provided by existing vaccines.
The agency could provide a faster timetable, similar to the way it approves vaccines against influenza.
In the US, licensed flu vaccines can be updated by substituting in new virus strains that are believed to be the most likely to cause illness in the coming flu season, without the need for large, randomised clinical trials.
Mr Hoge said the company expects the Omicron strain to have "an impact" on the effectiveness of its current vaccine.
The pattern of mutations recorded in the variant include those that have already been shown to reduce the efficacy of its shot in lab studies.
It is not clear yet how big an effect the variant will have on current vaccines, but it could be significant, he said.
"The mutations that had previously led to the biggest drops in efficacy were seen in Delta and Beta. And all of those mutations have shown up in Omicron," he said.
"And so the question here is: are we going to see a Delta-like performance? Are we going to see a Beta-like performance? Or are we going to see some cross-multiple of the two? I think it's that last scenario that has people most concerned."
Mr Hoge said the company was carrying out testing to determine whether people fully vaccinated with the current Moderna shot were protected against the variant, as well as those who received the 50-microgram and 100-microgram booster doses.
"I still believe that the existing vaccines will be able to at least slow down, if not completely stop, the Omicron variant," he said.