Novavax Inc.s Covid-19 vaccine was 96.4% effective against mild, moderate and severe symptoms of the disease in the final analysis of a late-stage trial in the U.K.

Shares of the drugmaker were up 16% in after-hours trading Thursday in New York. Since the start of this year, the stock had gained more than 68% through Thursdays close.

The company also released final results of a mid-stage trial from South Africa showing that its vaccine was 55.4% effective against a variant circulating there thats already been shown to partially elude the effects of some shots. Both studies reached their statistical goals, the company said in a

statement Thursday.

The company had

earlier said that its vaccine was 89.3% effective in the U.K., based on an interim analysis of the study of more than 15,000 people. An interim analysis of the South Africa data had shown it was 49.4% effective overall.

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