The UK has launched a study to examine whether using two different COVID-19 vaccines will work as effectively against the virus as using the same vaccine for both jabs.

The government has previously announced it will delay issuing the second jab by up to 12 weeks to vaccinate as many people as possible in the first round. 

If it decides to mix vaccines, the hope is that it will provide greater flexibility if there are supply issues from different pharmaceutical companies.

Matthew Snape, the study's lead researcher and associate professor in paediatrics and vaccinology at the University of Oxford, explained how someone could receive the Pfizer-BioNTech vaccine and then get the booster shot from the the Oxford University-AstraZeneca vaccine.

The CEO behind the Russian Sputnik V jab has already said that vaccine could be paired with others to boost resistance to the coronavirus. 

The study will discover whether the immune response it generates is as good, or better than, the current schedule.

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Meanwhile, a door-to-door testing program is under way in eight postcodes around the country to discover whether the variant that was first identified in South Africa has spread.

Firefighters and volunteers have been delivering COVID-19 test kits in neighborhoods in Maidstone, southeast England. They aim to test 10,000 people by the end of the week.

Operations Officer for UK Search and Rescue, Stuart Baird said people are worried.

"This is probably the worse crisis to hit the British public in generations." Baird said. "Almost exclusively, the residents have been fantastic, they are eager to have the test done and find out how far it has spread."

The UK is in a race against time to stop the spread of variants first identified abroad, for example in South Africa and Brazil, before they become widespread in the community and render vaccines less effective.

Sheila Bolt and her husband have received their first dose of the Pfizer/BioNTech vaccine and support the mass-testing program.

"I think it's a good thing and I think it's a shame they can't do it everywhere throughout the country so they can trace where it's spreading," Bolt said. "Obviously everybody is scared stiff."

Still, the lockdown and uncertainty is taking its toll on the community. From behind a window in her home, Tracey explained how bleak the situation is.

"Nobody had Christmas with their family and there doesn't seem to be a light," she said.

The British government is telling people to hold on and better days are coming as the vaccine is rolled out across the country.

But among dark and deserted streets in Maidstone, with a bitter winter chill in the air, that light seems far away.