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.