LONDON (REUTERS) - Novavax said on Monday (Feb 28) that an extended analysis of a late-stage study conducted in the United Kingdom showed that its Covid-19 vaccine provided long-term protection against the coronavirus.

The protein-based vaccine, NVX-CoV2373, continued to provide protection and maintained overall efficacy of 82.7% over a six-month period, the company said.

Additionally, vaccine efficacy of 82.5% was maintained against both symptomatic and asymptomatic infection, while vaccine efficacy against severe disease was 100%.

The analysis was conducted between November 2020 and May 2021 before the Delta and Omicron variants became dominant.

Novavax is working on developing an Omicron-specific vaccine and said on Monday it expects to begin manufacturing doses of the shot at a commercial scale in the first quarter.

The company did not disclose how many overall doses it expects to deliver in the first quarter, but forecast US$4 billion to US$5 billion in overall revenue in 2022.

Last year, Novavax reported data from its UK trial, where the vaccine was 89.3% effective in preventing Covid-19, with cases collected over three months.

"The vaccine offers protection against symptomatic and asymptomatic Covid-19 infection which may both interrupt virus transmission and prevent Covid-19 disease," said Gregory Glenn, president of research and development. "Additionally, we are encouraged to see that our Covid-19 vaccine maintains a high level of durable efficacy and continues to exhibit a reassuring safety profile in this extended timeframe."

Earlier this month, Britain approved the two-dose Covid-19 vaccine for use in adults. The vaccine is being reviewed by the US Food and Drug Administration and has received approvals from the European Union and the World Health Organization as well as countries including India, Indonesia and the Philippines.

The company earlier this month said its vaccine was about 80% effective in a late-stage trial in adolescents.