Moderna Inc on Tuesday said a COVID-19 booster designed to target the Beta variant as well as the original coronavirus generated a better immune response against a number of virus variants including Omicron.

Moderna said the results were a good sign for the company's plans for future shots targeting two COVID-19 variants.

Dr. Jacqueline Miller, a top Moderna scientist, said the company had no immediate plans to file for authorization of the bivalent vaccine including the Beta variant. It will submit the data to the US Food and Drug Administration in order to lay the groundwork for a future bivalent vaccine candidate that includes the Omicron variant as a target.

The company said the bivalent vaccine with Beta generated higher neutralizing antibody titers against the Omicron variant at one and six months after the shot was given than the booster of its original vaccine currently in use.

The company said it was especially encouraging that the bivalent vaccine induced higher antibody responses against variants that were not specifically included in the vaccine.

The 50-microgram bivalent booster, which the company calls mRNA 1273.211, was tested in 300 people.

Moderna has started testing a different bivalent shot that combines an Omicron-specific vaccine with its original. Initial data from that vaccine is expected later in the second quarter, Moderna said.

It is also testing a monovalent booster targeted at Omicron alone.

"In order to be ready for the fall, we've had to start manufacture at risk," Miller said. "Our belief is that the bivalent, based on the data that we have already observed ... offers the best hope for longer and more durable protection."