2. What are the different types of vaccines for the Coronavirus being tested in different parts of the world? Explain.
विश्व के विभिन्न भागों में कोरोनोवायरस के विभिन्न प्रकार के टीके कौन से हैं? समझाएं।
Demand of the question:
It expects students to explain different types of vaccines and for the Coronavirus being tested in different parts of the world.
As per WHO more than 160 vaccines are in development stage against coronavirus by research teams in companies and universities across the world. Researchers are trialling different technologies, some of which haven’t been used in a licensed vaccine before. At least six groups have already begun injecting formulations into volunteers in safety trials; others have started testing in animals.
All vaccines aim to expose the body to an antigen that won’t cause disease, but will provoke an immune response that can block or kill the virus if a person becomes infected. There are at least seven types being tried against the coronavirus, and they rely on different viruses or viral parts.
- Inactivated vaccine — The whole virus is killed with a chemical and used to make the vaccine. This is the same approach that is used to make the inactivated polio (shot), hepatitis A and rabies vaccines. e.g. Sinovac Biotech in Beijing has started to test an inactivated version of SARS-CoV-2 in humans.
- Subunit vaccine — A piece of the virus that is important for immunity, like the spike protein of COVID-19, is used to make the vaccine. This is the same approach that is used to make the hepatitis and human papillomavirus vaccines.
- Weakened, live viral vaccine — The virus is grown in the lab in cells different from those it infects in people. As the virus gets better at growing in the lab, it becomes less capable of reproducing in people. The weakened virus is then used to make the vaccine. When the weakened virus is given to people, it can reproduce enough to generate an immune response, but not enough to make the person sick. This is the same approach that is used to make the measles, mumps, rubella, chickenpox and one of the rotavirus vaccines. e.g. Oxford University vaccine, also referred to as AZD1222.
- Replicating viral vector vaccine — In this case, scientists take a virus that doesn’t cause disease in people (called a vector virus) and add a gene that codes for, in this case, the coronavirus spike protein. Genes are blueprints that tell cells how to make proteins. The spike protein of COVID-19 is important because it attaches the virus to cells. When the vaccine is given, the vector virus reproduces in cells and the immune system makes antibodies against its proteins, which now includes the COVID-19 spike protein. As a result, the antibodies directed against the spike protein will prevent COVID-19 from binding to cells, and, therefore, prevent infection. This is the same approach that was used to make the Ebola virus vaccine.
- Non-replicating viral vector vaccine — Similar to replicating viral vector vaccines, a gene is inserted into a vector virus, but the vector virus does not reproduce in the vaccine recipient. Although the virus can’t make all of the proteins it needs to reproduce itself, it can make some proteins, including the COVID-19 spike protein. No currently licensed vaccines use this approach.
- DNA vaccine : The gene that codes for the COVID-19 spike protein is inserted into a small, circular piece of DNA, called a plasmid. The plasmids are then injected as the vaccine. No currently licensed vaccines use this approach.
- mRNA vaccine:In this approach, the vaccine contains messenger RNA, called mRNA. mRNA is processed in cells to make proteins. Once the proteins are produced, the immune system will make a response against them to create immunity. In this case, the protein produced is the COVID-19 spike protein. No currently licensed vaccines use this approach. The US governments partially funded Moderna’s vaccine is based on mRNA approach.
It is likely that COVID-19 vaccines could have different levels of effectiveness in various subgroups of people. Because the elderly generally do not respond as well to vaccines, one or more COVID-19 vaccines may not work well for them. At present, three vaccine candidates are at the final stage of their trials. Among them, Oxford’s COVID-19 vaccine has shown a positive result in its initial trial.
Keeping in mind the pandemic situation, many of these research institutes and universities are working at a breakneck speed to develop vaccine. Though the they have adopted different approaches to develop the vaccine, in the end what matters is how effective the vaccine is; so that whole humanity can be saved from the disastrous impact of this global pandemic.