24th Jun 2020
24th Jun 2020
Curated by Endre Szvetnik
There are at least half a dozen COVID-19 vaccine candidates in development and testing. These include whole virus vaccines, recombinant subunit vaccines and next-generation nucleic acid vaccines
Whole virus vaccines use a weakened or disabled, non-replicating virus to provoke an immune reaction in the patient against the novel coronavirus. One such vaccine, developed at Oxford University is ChAdOx1 nCoV-19 (a version of adenovirus causing the common cold) has commenced trials in the UK and South Africa. The concept is to use the ChAdOx1 gene to promote the production of the ‘spike protein’ of the novel coronavirus (which attacks our cells), with added genetic material. It is hoped that the vaccine will help the immune system recognize the coronavirus, create the antibodies that attach to the spike protein thus stopping the virus from entering into cells. The drawback of such whole virus vaccines is that usually, they call in a weaker immune reaction, so people may need several ‘booster shots’ and not just one dose to get immunity.
What are the other vaccine groups?The other two main groups are subunit vaccines (an established technology) and nucleic acid vaccines (the first such vaccine passed its first clinical trial in May). Subunit vaccines contain only parts of a virus, made in the lab. In the case of SARS-CoV-2, this part is the often-mentioned spike protein. By injecting a ready-made component of the virus into the human body it is easier to provoke a faster and stronger immune reaction than with whole virus vaccines. The benefit of subunit vaccines is that they can be administered to COVID-19 patients with weakened immune systems who are at risk of having a severe or critical form of the disease. Nucleic acid vaccines are a radically new technology where no human vaccine has been licensed yet. The idea here is not to introduce viruses or virus parts to stimulate an immune reaction. Instead, DNA or RNA molecules with copies of the virus’s genetic code are injected into cells to produce antigens, or ‘infectious agents’ similar to the virus. Once the antigens appear, our immune system produces antibodies. These either attack the virus (if we are sick) or develop a memory of the specific pathogen, so if the same virus infects us, the antibodies can identify and attack it faster. The benefit of this technology is that it’s cheap and fast (mRNA molecules for the vaccine can be created by sequencing current virus samples in the population). In animal experiments, researchers managed to provoke immune reactions to various infectious agents, such as influenza virus, hepatitis B virus, HIV and rabies virus.
Here is the current state of science on a Sparrho pinboard. NB: The pinboard contains research papers that have not been peer-reviewed yet, meaning that they have not gone through the standard scientific validation process yet.
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