Clive Dix, who leads the group which managed Britain’s vaccine procurement strategy, said more vaccines would be approved for use in the “very near future”.
The UK has so far vaccinated 15.6 million people with a first dose and 546,165 with a second dose, the fastest roll-out per capita of any large country so far.
Asked how long it would take the UK to give two doses of the vaccine to all adults, he replied: “We’re probably talking August time or September time all done, maybe sooner if we need to.”
“We’ve got to deliver just over 100 million doses of vaccine and I believe we should be able to do that. I’m not in deployment so I can’t look at the numbers of when they will be. But if they need to be deployed by then, we’ve got the vaccine to do that.”
The Department of Health and Social Care (DHSC) said testing regimes will be set up in Norfolk, Southampton and Woking, Surrey, where positive cases of South African variant have been discovered.
The testing will be targeted within the postcodes of IP22, SO15 and GU22 in those areas respectively.
Efforts in Manchester to track down examples of the mutation of the more transmissible Kent variant will also be expanded following deployment of testing teams last week, with the postcode districts of M40 and M9 set to be targeted.
Some 10,000 extra tests were rolled out in areas of the city last week after four people from two unconnected households were found to be infected with the E484K mutation, which is linked to the Kent variant mutation.
Laboratory studies have shown that viruses with the E484K mutation, which is also found in the South African variant, can escape human defences, making them more efficient at evading natural and vaccine-triggered immunity.
Public Health England data shows that 217 confirmed or probable cases of the South African variant have been discovered – a rise of 15 since the last update on February 11.
People living within the targeted testing areas are strongly encouraged to take a Covid-19 test this week, whether they are showing symptoms or not, a spokeswoman for the department said.
People with symptoms should book a test in the “usual way”, and those without symptoms should visit their local authority website for more information, she added.