A new single-injection COVID-19 vaccine has shown good potential in trials, according to its Belgian developer. And new trials in the UK have shown an efficacy rate of 89 percent for another, produced by Novavax in the UK. 

Belgian pharmaceutical firm Janssen said their single-jab vaccine is 66 percent effective, although doubts remain over how well it can defend against newer variants. But crucially, without a need for a second injection, this vaccine would avoid some of the administration challenges linked with other vaccines. Supply would also go twice as far. Janssen is owned by Johnson & Johnson. 

Several other vaccines have been rolled out in other countries. Sinopharm, one of the pharmaceutical companies developing a vaccine in China, says the results of its phase three trials show it is 79 percent effective, while the makers of Russia's Sputnik-V vaccine say it is also highly effective.

The vaccines use different types of technology to stimulate an immune response from the body and protect people from becoming ill with COVID-19. Here we explain how they work.

Novavax

How does it work? 

It's slightly different from the vaccines which have been approved so far, but the broad goal of triggering the body's immune system to elicit a response against the "spike protein" on the virus remains the same. 

The Novavax jab uses a lab-made protein, and an "adjuvant," which help prompt a human immune reaction. It involves two injections, which the makers recommend to be taken three weeks apart. 

How effective is it?

Phase 3 trials in the UK have shown the Novavax vaccine is 89 percent effective against the original COVID-19 virus. Crucially, it has also shown effectiveness against the "new" varients found around the world. 

Trials in South Africa suggest it is 60% effective against the strain thought to have originated there. 

How is it stored?

It can be stored at domestic fridge temperature. 

Janssen

How does it work?

This vaccine uses a common cold virus which has been genetically engineered to cause no harm to humans. Using the cold as a host, the Janssen vaccine delivers part of the COVID-19 genetic sequence into the body. This alerts the body to the new coronavirus without putting patients at high risk. 

How effective is it?

A single dose is 66 percent effective, on average. In trials in the U.S. it was recorded as 72 percent effective at stopping infections, but it was only effective in 57 percent of cases in South Africa, perhaps owing to different virus varients. 

How is it stored?

A single dose at regular fridge temperature can give the 66 percent level of protection, according to the study. This could speed up delivery around the world, but the firm is also experiementing with a second injection, to see if that boosts immunity further. 

Oxford-AstraZeneca

How does it work?

Scientists have taken genes from the spike protein on COVID-19 and inserted them into a harmless common cold virus to create their vaccine. When injected into the body, cells begin to reproduce the spike protein. This immune system retaliates by producing antibodies and creating T-Cells to destroy those cells and prevent the person from falling ill. If the person is infected with COVID-19 at a later date, they now have antibodies and T-Cells to deal with it. Two doses of the vaccine are meant to be 62 percent effective.

How effective is it?

Results from trials using two doses of the vaccine taken up to three months apart found it to be 62 percent effective – that's higher than the seasonal flu vaccine which is roughly 50 percent effective. Scientists are now waiting to see if the vaccine stops transmission of the virus.

How is it stored?

The vaccine can be transported and stored in normal fridges, meaning it can be distributed more quickly and speed up vaccination programs.

Pfizer-BioNTech and Moderna

How does it work?

These two vaccines use the same innovative mRNA technology, which works differently from the traditional approach used to create the Oxford jab. Rather than injecting the virus into a person, the vaccine instead introduces the body to a messenger sequence, which gives the immune system instructions to create its own antigens – the cells that prompt the immune system to produce antibodies and T-Cells to fight COVID-19.  

How effective is it?

Results from Pfizer trials showed it to be 95 percent effective within 28 days of the first dose. As with the Oxford vaccine, the second dose is required for longer-term immunity. The Moderna results gave it an effectiveness of 94.5 percent.

How is it stored?

One of the drawbacks of the Pfizer vaccine is that it must be kept at minus 70 degrees Celsius during transportation. The Moderna jab can be stored in normal fridges for up to 30 days and at room temperature for 12 hours. It's also stable at minus 20 degrees Celsius for up to 12 months.

Sinovac and Sinopharm

China's Sinovac and Sinopharm vaccines use the same approach as the Oxford vaccine to provide immunity from COVID-19. Killed viral particles from the virus are injected into the body, which triggers an immune response and stops a person from falling seriously ill when they contract COVID-19.  

How effective is it?

On Wednesday, Sinopharm said results from trials showed its vaccine to be 79 percent effective and it has already been approved in the United Arab Emirates. Researchers in Brazil say the Sinovac vaccine is more than 50 percent effective.

How is it stored?

Just like the Oxford vaccine, both jabs can be stored at regular fridge temperature, which will also make it easier for poorer nations to transport and store the vaccine.

Sputnik-V

How does it work?

The Sputnik-V vaccine uses an inactivated virus, just like the Oxford, Sinovac and Sinopharm vaccines to stimulate an immune response from the body. 

How effective is it?

Trials showed the vaccine proved to be more than 90 percent effective in individuals aged over 60 years, according to the makers. Further tests are ongoing to see if it has the same impact on different age groups.

How is it stored?

Standard household fridges in dry form.