NEW YORK( BLOOMBERG) - Chances are roughly one in five that new Covid-19 variants will arise that are more dangerous than the current versions, Moderna's chief executive officer said.

The more likely scenario is that vulnerable people, such as the elderly and immunocompromised, will need annual boosters for protection against strains that are similar in virulence to Omicron, Moderna CEO Stephane Bancel said Thursday (March 24) in an interview with Bloomberg TV.

The CEO spoke on the day of a company event detailing its research and progress with messenger RNA vaccines.

Moderna is working to reassure investors about its longer-term growth prospects as the new cases decline following the winter spread of highly transmissible Omicron.

However, Omicron's BA.2 subvariant continues to circulate, leading to concerns about a resurgence and the emergence of new strains of the virus with greater power to infect and sicken.

"I think there's an 80 per cent chance that the variants that we're going to see in the future are manageable from a severity standpoint and vaccine production," Mr Bancel said in the interview.

"But I think we should always be very cautious, because there's a 20 per cent chance that something happens in some of the new variants that is very virulent."

On Wednesday, Moderna said it would apply for clearance for its Covid vaccine in kids under 6 after the shot generated strong immune responses in a big pediatric trial.

Mr Bancel said that authorization of Moderna's vaccine in very young children is more likely to come first in Britain or other countries abroad.

Clearance in young children could take a bit more time in the US, he said, where Moderna's vaccine isn't yet cleared for children of any age.

During Thursday's virtual investor meeting, Moderna said that interim data from a mid-stage trial of its first influenza vaccine indicated it was safe and generated an immune response.

The results suggest the experimental flu shot may be superior to existing vaccines for influenza A, the strain accounting for most adult case, officials said.

The company also said it expects its combination influenza and Covid-19 vaccine to begin human trials this year.

"I believe we're going to get to a very high efficacy flu shot on the market," Mr Bancel said on Bloomberg TV.