Novavax's COVID-19 vaccine could be authorized as early as May, its CEO said. A trial suggests it is 89% effective, though slightly less so against contagious variants.

• Novavax CEO Stanley Erck predicted his company's vaccine could be authorized in the US in May.
• He said the timing depended on whether the FDA would act largely based on UK trial data.
• Late-stage UK trials suggest the vaccine is highly effective, though a bit less so against variants.

Novavax CEO Stanley Erck has predicted that the company's coronavirus vaccine could be authorized in the US as soon as May.

Trial results suggest the vaccine is highly effective, though less so against the variant first found in South Africa that has spread to at least 10 US states including New York.

The American biotech company has agreed to supply 110 million doses of its vaccine to the US, Erck told CNBC on Monday, adding that he expected them to be delivered by June or July. But he said this depended on whether the US Food and Drug Administration issued an emergency-use authorization for the vaccine based largely on trial data from the UK.

Novavax is running three efficacy trials at same time, Erck said: in the UK, South Africa, and the US. Data from the US phase-three trial, which has 30,000 participants, won't come out for "probably a couple of months," he said.

Novavax already has phase-three trial data on the vaccine's efficacy in the UK, however, suggesting the shot is on average 89.3% effective at protecting against COVID-19.

The UK trial of 15,000 participants found the vaccine to be slightly less effective against the B.1.1.7 strain, first identified in the UK and now spreading rapidly in the US. Novavax said roughly half of the participants who caught the coronavirus during the trial were infected with this variant, and the vaccine was 85.6% effective on them, compared with 95.6% on the original strain of the virus.

"It did show there's a decrement as the virus mutates," Erck told CNBC.

In a trial in South Africa, interim results show the vaccine was far less effective against the B.1.351 strain, which was first found there.

Erck said Novavax would probably file for approval in the UK first, in about April, before submitting data to the FDA about a month later.

"Our hope and expectation is that the FDA will agree to review the [UK] data as part of our EUA filing in the US," he said.

FDA regulators have so far given emergency-use authorization to three coronavirus vaccines in the US, developed by Johnson & Johnson, Moderna, and Pfizer and BioNTech.

"I'm not worried about lack of demand for the vaccine even though we'll be the fourth vaccine," Erck told CNBC. "There's plenty of additional need for the vaccine in the US, and it's a big world."

The company is also looking at filing in Canada and Australia, he said. Novavax so far has advance-purchase commitments to ship 200 million doses outside the US "with the expectation that there'll be a lot more on top of that," he said.

In February, Novavax also said it would supply more than 1.1 billion doses of its vaccine to COVAX, a global World Health Organization-backed initiative to guarantee fair and equitable vaccine distribution.

Novavax has said it hopes to produce its shot at a rate of 2 billion doses a year by the middle of 2021, though it's not clear how many shots the company could actually make this year.

Compared with the Moderna and Pfizer-BioNTech vaccines, Novavax's shot can be stored at normal fridge temperatures rather than freezing temperatures, Erck told CNBC. But people should get whichever vaccine is available to them, he said.

"All these vaccines work," he said, "and if they're available, people should take them."