Surge testing is taking place in four London boroughs after cases of the Covid-19 South African variant were found.
Residents in some parts of Southwark and Barnet have become the latest to be targeted, with those in certain areas within the SE16 postcode in Southwark and N3 postcode in Barnet being urged to get tested.
They join two other London boroughs – Wandsworth and Lambeth, where 44 confirmed and 30 probable cases were identified.
People aged 11 and over in the four boroughs are being urged to take a PCR test even if they have no symptoms.
Health chiefs believe the SA mutation may be more resistant to vaccines but the jabs, including the Oxford/AstraZeneca, Pfizer BioNTech and Moderna inoculations which have been approved in the UK, are thought to still offer significant protection against severe disease.
The Department of Health and Social Care said the case in Barnet was unrelated to other clusters, but it had been isolated and the person’s contacts traced.
According to the BBC the SA variant outbreak may initially have been triggered by a person who travelled from an African country, not South Africa, to the UK in February.