COVID-19 Vaccines: Scientists Use 8 Different Ways To Provide SARS-CoV-2 Immunity

Over 90 different vaccines are currently being developed against the deadly novel coronavirus by researchers in companies as well as universities worldwide. Each of them is trying different technologies and some of them haven’t even been used in a licensed vaccine by far.

While some of them have already started injecting their vaccine formulations into volunteers in safety trials, certain others have started testing in animal models.

There are at least eight different types of vaccines being tried against the coronavirus and the Nature journal’s new graphical guide explains how each of these vaccines is designed.

The vaccines are of 4 main types namely Virus vaccines, viral vector vaccines, nucleic acid vaccines, and protein-based vaccines. And each of these 4 has 2 different subtypes each.

1. Virus Vaccines- Those vaccines that use the virus itself either in a weakened or inactivated form. Many existing vaccines including the measles and the polio are designed in this method. Sinovac biotech in Beijing is currently testing an inactivated version of SARS-CoV-2 in human trials.

i) Weakened virus vaccines: Viruses are weakened by being passed via animals or human cells until it picks up mutations that reduce its ability to cause an infection. New York-based firm Codagenix is collaborating with the Serum Institute of India to weaken the SARS-CoV-2 by altering its genetic code.

ii) Inactivated virus vaccine: The viruses are made uninfectious by treating them chemically, or by using heat. This method requires large quantities of the virus.

2. Viral- vector vaccines- Viruses such as measles or adenovirus are genetically engineered in order to produce the coronavirus proteins in the body. They are then weakened so that they cannot be infectious. They are of two types namely:

i) Replicating viral vector vaccines: Vaccines similar to weakened measles can still replicate within cells. They tend to be safe and provoke a strong immune response.

ii) Non-replicating viral vector vaccines: These are vaccines that cannot replicate within cells since key genes have been disabled. Even though no licensed vaccine uses this method, Johnson & Johnson is currently working on this approach.

3. Nucleic-acid vaccines- These vaccines use genetic instructions for a coronavirus protein to promote an immune response.

i) DNA vaccine: Pores are created in the cell membranes to increase the uptake of DNA into a cell via a process called electroporation.

ii) RNA vaccine: RNA is encased in a lipid coat so that it can enter the human cells to churn out copies of the virus protein.

4. Protein-based vaccines- Coronavirus proteins are injected directly into the human body to generate an immune response. Protein fragments or protein shells mimicking the virus’s outer coat are also used.

i) Protein subunits vaccines: These are vaccines with viral protein subunits such as the receptor-binding domain or the virus’s spike protein. Similar vaccines against the SARS virus have been effective in animal models but haven’t been tested in human beings.

ii) Virus-like particles vaccines: Particles such as those empty virus shells which mimic the structure of coronavirus but aren’t infections due to the lack of genetic material are injected into human cells to trigger an immune response.