While the infections are rising, there has not been a corresponding rise in the number of hospitalizations with COVID-19, indicating that the vaccinations are effective against the highly transmissible variant first identified in India, Public Health England (PHE) said.

Of the 50,824 cases of Delta B1.617.2 variant over the past week, 42 are from the Delta AY.1 sub-lineage with the mutation K417N which is feared to be more vaccine-resistant.

"Cases across the UK continue to rise and it is incredibly important that we do not forget to be careful," said Dr. Jenny Harries, Chief Executive of the UK Health Security Agency.

"Although cases are rising, we are not seeing a proportional rise in the number of people who are being admitted to hospital. The data suggest this is testament to the success of the vaccination program so far and clearly demonstrates the importance of getting both doses of the vaccine," she said, urging people to come forward for their vaccines.

"It will help us to break the chain of transmission, and it will save lives," she said.

The genomic sequencing data released by PHE weekly on the variants of concern (VOCs) and variants under investigation (VUIs) show that the Alpha VOC, first identified in the English county of Kent, accounts for the second-highest infections in the country.

An additional 823 COVID-19 cases were logged off the Alpha VOC, followed by 11 of the Beta VOCs first detected in South Africa.

The latest data comes as the UK recorded 27,989 new daily cases of coronavirus on Thursday, with Prime Minister Boris Johnson indicating that "extra precautions" may have to stay in place as the country prepares to lift lockdown restrictions on July 19.

The government is also expected to review the travel list again this month, with only a few countries on the green list of free travel at the moment, while much of Europe remains on the amber list.

Meanwhile, India along with South America and Africa, and most other countries remain on the travel ban red list, requiring compulsory hotel quarantine for British residents.