The European Union on Monday approved the use of Novavax's COVID-19 vaccine in people 18 years and older, giving a boost to the U.S. biotech after long delays and paving the way for a fifth shot in the EU as the omicron variant spreads.

Data from two large studies showed the vaccine has an efficacy of around 90%, the European Medicines Agency (EMA) said.

It is not clear yet how Novavax performs against the omicron variant, or whether a booster dose will be needed. Some early data has suggested that many two-dose vaccines do not work well against the variant while a third shot improves their efficacy.