Chart of the day: How do the different COVID-19 vaccines work?

The approval of the first COVID-19 vaccines has renewed hope across the world that the battle against the pandemic that has so far killed more than 1.6 million people may eventually be won.

No single vaccine is likely to be distributed globally; instead a range of treatments will be used. Here are two of the different vaccines and how they work.

The Pfizer-BioNTech vaccine

This RNA vaccine – one of the world's first to be approved – was developed by US pharmaceutical giant Pfizer and its German partner BioNTech. Its active ingredient is messenger RNA, which is closely related to DNA and contains a synthetic version of COVID-19’s genetic code.

Once injected, the patient’s immune cells follow the vaccine’s instructions to build the coronavirus ‘spike’ protein. Their body then launches an attack against it, thereby learning how to defeat the real virus. The vaccine, which requires two doses, has 95% efficacy rate. However, a significant drawback is that it needs to be stored at -70C.

The Pfizer-BioNTech vaccine received authorization for use by the UK regulator on 2 December. It has also been approved in other countries, including the US, Canada and in the European Union. US company Moderna has also developed an RNA vaccine, which has also been approved for use in the United States.

The Oxford-AstraZeneca vaccine

This viral vector vaccine was developed by the University of Oxford and AstraZeneca and works by altering a harmless adenovirus so it contains the genetic code for the coronavirus spike protein.

The adenovirus is then injected into the body, where it transports the genetic instructions into the patient’s cells. These then start to produce the protein, triggering an immune response and priming the body to attack the real virus later.

The Oxford-AstraZeneca vaccine – which also requires two doses – has been approved for use in the United Kingdom. Research suggests that it could be up to 90% effective. It is both cheaper than its rivals and easier to store, meaning it could play a vital role in fighting the pandemic worldwide.