The COVID-19 pandemic has seen possibly the largest cohort of vaccine candidates than any other virus in history. More than 100 candidates are at various stages of development, but only four are the closest to becoming a possible solution to the current pandemic.

The AstraZeneca, CanSino, Moderna and Sinovac vaccines are the furthest along, however since the vaccine approval process is so rigorous, being at this later stage doesn’t mean they will make it all the way through. In addition, even if they are approved, scaling a vaccine will depend on investment, how it’s made and there is always the threat that governments where the vaccine is made could make it hard for other countries to access them.


This vaccine has been developed in China with the Beijing Institute of Biotechnology and had successful phase two trials. It is a viral vector vaccine which means it uses an adenovirus, the common cold virus, to deliver the coronavirus spike protein into the body and prompt an immune response. It has been approved for use by the Chinese military and is currently in phase three trials.


This is the most well-known trial for South Africans as it is the one the country is participating in. The University of Oxford also developed a viral vector vaccine. This means it is a modified virus, in this case a chimp adenovirus, which contains the genetic sequence of the spike protein which is also found in the coronavirus. This then allows the human body to identify this protein and prompts an immune response, without being exposed to COVID-19.

The pharmaceutical firm AstraZeneca is supporting the production of this vaccine and the phase three trials are happening in South Africa and Brazil.


The Moderna vaccine is different to the others as it is an entirely new kind of vaccine. Rather than using another virus as a vector, it is a synthetic version of the coronavirus spike protein’s RNA. This, when injected, is hoped to trick the body into making the spike protein itself to produce the immune response. After a successful phase two which saw no major safety concerns, phase three is expected to begin soon in the US.


Another Chinese-based vaccine, CoronaVac, was developed by Sinovac Biotech and is an inactivated vaccine. This means that it is made up of virus particles that have been killed or inactivated so they can no longer cause infection. This is what most people still think vaccines are, but as the others show, is not the most popular vaccine method anymore. The inactivated vaccine aims to provoke an immune response by having the immune system acknowledge these dead virus and then recognising their similar live virus should they enter the body.

It’s phase one and two studies were positive and it is now moving onto phase three with tests in Brazil.

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