In a House of Commons statement on 26 November, Mr Javid warned that the new variant could be 'more transmissible than the Delta variant and current vaccines may be less effective against it'.
No cases have been identified in the UK at this stage, but the variant has already spread to countries around the world.
B.1.1.529 was first identified in Hong Kong in a case involving a person who had travelled from South Africa.
South Africa has seen a four-fold rise in COVID-19 cases in the past two weeks, Mr Javid said, the majority associated with the new variant.
He said the variant had been detected in Botswana as well as in South Africa and that it was 'highly likely that it has now spread to other countries'.
Mr Javid's statement in parliament came as reports emerged that a case of the new variant had been detected in Israel.
The health and social care secretary said: 'Over the past 48 hours, a small number of cases of a new variant have been detected on our international genomic database.
Variant of concern
'I want to reassure this House that there are no detected cases of this variant in the UK at this time but this new variant is of huge international concern.'
Mr Javid said the situation regarding the new variant was 'fast-moving' and that significant uncertainty remained.
But he warned: 'We are concerned that this new variant may pose a substantial risk to public health. The variant has an unusually large number of mutations.
'Yesterday, the UK Health Security Agency classified B.1.1.529 as a new variant under investigation and the Variant Technical Group has designated it as a variant under investigation with very high priority.
'It’s the only variant with this designation, making it higher priority than Beta. It shares many of the features of the Alpha, Beta and Delta variants.
'Early indications show this variant may be more transmissible than the Delta variant and current vaccines may be less effective against it. It may also impact the effectiveness of one of our major treatments, Ronapreve.'
The health and social care secretary said the UK was in a 'strong position', having delivered more than 113m doses of COVID-19 vaccine over the past year.
He urged people to continue to come forward for vaccination - and set out travel restrictions the government has imposed on countries in southern Africa.