Covid vaccine


This article describes 8 different approaches towards the development of a COVID-19 vaccine.




May 02, 2020: Vol 20 No 53


By April 08, 2020, there were at least 115 COVID-19 vaccine candidates of which 73 were in laboratory stages of development and 5 were in clinical development (Le et al, 2020). Callaway (2020) provided a further update.

Important updates are:

1. At least 6 teams working on COVID-19 vaccines have begun safety trials in human volunteers.

2. Some of the vaccines under development involve technologies that have never before been used in a licensed vaccine.

3. Presently, there are 8 different vaccine approaches. These include the use of inactivated or weakened virus; the use of replicating or non-replicating viral vectors; the use of vaccines with DNA or RNA; and the use of vaccines based on protein subunits or virus-like particles.

4. Weakened viruses are produced by repeatedly passing the virus through animal or human cells until mutations arise that make the virus less pathogenic.

5. Inactivated viruses are produced by treating the active virus with chemicals or heat; this requires a large reservoir of the virus for vaccine production.

6. A replicating viral vector uses a different, genetically-engineered, weakened virus, such as a weakened measles virus. This viral vector can replicate within human cells and can produce coronavirus proteins in the body. The coronavirus proteins elicit an immune response. Whereas the approach is safe and can elicit a strong immune response, its effectiveness can be blunted if the patient has strong immunity against the viral vector.

7. A non-replicating viral vector is similar, except that the virus does not replicate in the body and so booster injections are required to produce long-lasting immunity.

8. DNA and RNA vaccines use genetic instructions in the form of DNA or RNA, injected into human cells, resulting in the production of viral protein in the body.

9. Protein-based vaccines involve the direct injection of coronavirus proteins or parts thereof, such as the spike protein or the receptor binding domain of the spike protein.

10. Vaccines based on virus-like particles involve the injection of the virus protein shell or a part thereof; because there is no viral RNA in the vaccine, the vaccine will not produce disease.

11. Most of the work is being conducted by private and industrial organizations, most of which are in North America.

12. The COVID-19 vaccine could be at least 18 months away.


Callaway E. The race for coronavirus vaccines: a graphical guide. Nature 2020; 580: 576-577

Le TT, Andreadakis Z, Kumar A, Roman RG, Tollefsen S, Saville M et al. The COVID-19 vaccine development landscape. Nature Rev Drug Discovery 2020; doi: 10.1038/d41573-020-00073-5.

Leave a Reply

Fill in your details below or click an icon to log in: Logo

You are commenting using your account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s

%d bloggers like this: