As the rest of the world gradually lifts COVID restrictions, China continues to lock down enormous parts of society and conduct mass testing to eradicate the coronavirus. It has not approved any foreign COVID vaccines and relies on several domestically developed shots.

"We are open, we have the capacity", Bancel told Reuters on the sidelines of a media conference in Tokyo about supplying its mRNA-based shots to China, declining to say whether Moderna had submitted its vaccine for approval there.

A Moderna spokesperson said those discussions had happened in the past and it could not comment on whether those talks were still ongoing.

There is about a 20 percent probability that a "problematic" variant of the virus could emerge this winter, Bancel said, adding it was not his base case scenario.

"We should just always be humble about biology," he said.

Bancel, speaking in Tokyo, said Moderna was considering building facilities in Japan to produce mRNA-derived products.

Japan on Monday approved vaccine boosters from Moderna and Pfizer Inc that target the Omicron variant of the coronavirus.

Moderna sued Pfizer Inc and its partner BioNTech last month for patent infringement in the development of the first COVID vaccine approved in the United States. 

Moderna believed from the beginning of the outbreak that BioNTech was using its technology and patents, but decided to wait until the pandemic subsided to file suit, Bancel said.