A group at the University of Oxford’s Jenner Institute have recently put together a summary in the BSI's journal Immunology of the progress made so far in the development of a vaccine for COVID-19.
COVID-19 is the disease caused by the virus SARS-CoV-2. The World Health Organization declared a global pandemic on 11 March 2020 and at the time of writing this article, the spread of COVID-19 around the world had led to hundreds of thousands of deaths in 200 countries. The development of a vaccine is now a major focus for scientists around the world; a safe and effective vaccine is urgently needed against this highly transmissible disease. The review highlights that there are over 100 vaccine candidates currently being developed, using a range of approaches. They include:
1. Whole virion vaccines
This approach can be divided into two categories – ‘live attenuated’ and ‘inactivated’. Both types ‘introduce’ the immune system to a ‘whole pathogen’ in a way that it can safely learn to recognise it as a hostile invader, produce antibodies, and remember it for the future. The difference between the two types is that live attenuated vaccines (LAV) introduce a weaker form of the live virus into the body that will enable the immune system to ‘learn’ how to fight it without causing illness, whereas inactivated vaccines use a form of the virus which has been killed (often by exposure to chemicals or heat).
2. Protein subunit vaccines
This group of vaccines introduce protein molecules taken from the target virus (known as antigens) into the body to induce a protective immune response. The approach avoids handling highly dangerous live viruses. This type of vaccine is usually administered with an adjuvant – this is a particular ingredient or substance which helps to create a stronger immune response in people receiving the vaccine.
3. Nucleic acid vaccines
These vaccines contain the genetic material, DNA or RNA, that code for a specific protein from the virus. When the vaccine is given, the body’s cells use the DNA or RNA contained in it to produce the virus protein, which is then recognised by the immune system as foreign and generates an immune response. Two COVID-19 vaccine candidates that have been developed using this approach in the US are currently undergoing clinical trials.
4. Recombinant viral-vectored vaccines
This type of vaccine uses a DNA molecule as a vehicle to introduce genetic material from the target pathogen into the body. The viral vehicle, known as a vector, is constructed from a genetically-modified harmless virus. Again, the body’s cells produce the virus protein from the genetic material and the immune system ‘learns’ to identify and combat the infection. This kind of viral-vectored vaccine technology is being used to develop a COVID-19 vaccine by the Jenner Institute and the Oxford Vaccine Group in the UK. The vaccine uses a chimpanzee adenovirus viral vector and clinical trials of this vaccine candidate on healthy volunteers are already underway.
Vaccines have to undergo rigorous clinical trials before they can be rolled out to the general public. Such trials need to prove vaccines are safe, and that they induce a significant and lasting immune response to the SARS-CoV-2 virus in the human body. Clinical trials have been started for a small number of the COVID-19 vaccine candidates (including the one at Oxford’s Jenner Institute mentioned above), and more trials are expected to start around the world over the next few months.
With vaccine research advancing at unprecedented speed in response to the COVID-19 pandemic, there is hope that the timeline for the development of a safe and effective COVID-19 vaccine can be reduced to 18 to 24 months. This compares favourably with the average vaccine development time of ten years. However, vaccine hesitancy needs be addressed and the public should be made aware that full and extensive safety and regulatory requirements have been completed with extreme care, even of a new and rapidly developed vaccine for COVID-19. The public will need to have confidence in these new vaccines. The authors of the review also highlight the need for a strategic approach to vaccine funding and development that ensures it can be manufactured and distributed on a global scale, at an affordable cost to all countries.
Sharpe, H.R., Gilbride, C., Allen, E., Belij‐Rammerstorfer, S., Bissett, C., Ewer, K. and Lambe, T. (2020), The early landscape of coronavirus disease 2019 vaccine development in the UK and rest of the world. Immunology 160: 223-232. doi:10.1111/imm.13222
First published 27 May 2020
Summary author Penny Fletcher