Pfizer and BioNTech have said a booster jab of their coronavirus vaccine promises to be an effective defence against the new Omicron variant.
Three doses provide a similar level of antibodies against Omicron to that of two doses with other variants, the companies said after a small study.
The World Health Organization (WHO) earlier said vaccines should still work against severe Omicron cases.
Researchers across the world are piecing together data about Omicron.
It is the most heavily mutated version of coronavirus found so far.
In a statement on Wednesday, Pfizer chief executive Albert Bourla said protection against the variant would be improved with a third dose of the jab.
“Ensuring as many people as possible are fully vaccinated with the first two dose series and a booster remains the best course of action to prevent the spread of Covid-19,” he said.
However, Pfizer and BioNTech noted that the results were preliminary and said they would continue to collect data and “evaluate real-world effectiveness”.
They added that they were developing an Omicron-specific vaccine which would be ready for delivery within 100 days, pending regulatory approval.