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About 200 kinds of COVID-19 vaccines are being actively developed. All vaccines have a main goal: prepare a person’s immune system to prevent the body from resisting it when it encounters invading organisms.
To this end, the vaccine provides the immune system with something that looks like an intruder, and is basically harmless, but it will still trick the body into forming an immune response, thus countering the actual virus when it appears. It’s a bit like showing someone a picture and saying, “If this person appears at your door, don’t let them in.”
There are many ways to make the virus a “picture”, and COVID-19 vaccine developers are pursuing all of them.
Inactivated virus vaccine
This method has been around for decades. Jonas Salk used it to make a polio vaccine. The researchers used the virus of interest for heating or treatment with chemicals such as formaldehyde. This makes it no longer able to cause disease, but it can still display proteins on its surface, and the immune system can recognize it as an intruder.
Four companies in China have begun to use this method for clinical trials: Wuhan Institute of Biological Products; Beijing Institute of Biological Products; Chinese Academy of Medical Sciences and Sinovac Research and Development.
One disadvantage of the inactivated virus method is that the vaccine does not always produce a strong enough immune response to effectively resist the virus, and sometimes a second dose is needed to obtain protection.
Live attenuated vaccine
This is also a well-known method. Here, the virus has been modified or attenuated in the laboratory, in a sense it can still “live” because it can still infect cells, but rarely can spread quickly and cause disease. This is how the Sabine polio vaccine works.
These vaccines can produce a strong immune response, but in some cases, they can also cause the disease they are trying to prevent, because the weakened virus can sometimes be harmful to people with weakened immune systems.
The list of vaccine candidates prepared by the World Health Organization includes only three companies developing live attenuated vaccines.
Non-replicating viral vector vaccine
Instead of killing or modifying As a virus used in vaccines, researchers can only use proteins produced by the virus that stimulate the immune system.
Once the researchers know the complete gene sequence of the virus, isolating the genes for those proteins is relatively simple. But how do these genes enter human cells without actual or attenuated viruses?
One method involves turning to other viruses, which are not necessarily related to the virus that causes the disease. There are many viruses that infect humans, but cause little or no disease. Researchers can extract genes from coronaviruses to make proteins that stimulate the immune system, and then put these genes into one of the harmless viruses. Once the harmless virus enters the cell, it transmits the coronavirus gene (essentially, the point), and the cell faithfully produces the coronavirus protein, which triggers an immune response.
As a safety measure, researchers can modify the harmless virus so that it does not replicate itself after passing its genetic payload to the cell.
Oxford University has partnered with pharmaceutical company AstraZeneca to develop a vaccine that works this way. The drug candidate is already undergoing efficacy testing to see if it can actually prevent COVID-19. Together with the Institute of Biotechnology, Chinese Academy of Military Medical Sciences, CanSino Biologics also has a vaccine that works in human trials.
Replication virus vector vaccine
Similar to non-replicating viral vector vaccines, the viruses used in these vaccines are either harmless to human nature or harmless to humans. Like non-replicating viral vectors, these replicating viral vectors have been modified to include instructions for making viral proteins that can stimulate someone’s immune system. The difference is that these viruses do retain the ability to replicate themselves. This means that they can continue to pump out coronavirus proteins, thereby keeping the immune system activated and ready to react when the coronavirus appears.
Merck successfully used this technology to manufacture the Ebola vaccine, which was approved last year and is being tested with the candidate COVID-19 vaccine.
Virus-like particle vaccine
It sounds like virus-like particles are aggregates of proteins, similar to viruses, but without genetic instructions to replicate themselves. Several companies are using these virus-like particles to make vaccines. One is Medicago in Quebec City, which uses plants to produce virus-like particles.
DNA is usually a chemical substance that stores genetic instructions passed from one generation to the next. In order to produce proteins in accordance with these instructions, it is necessary to convert DNA into RNA-specific proteins are made from specific strands of RNA.
For RNA vaccine candidates for COVID-19, the specific strand of RNA is a strand that forms a protein called spiny protein on the surface of the coronavirus. The spike protein enables the virus to insert itself into cells in our body. The idea behind this vaccine is to inject RNA sequences into someone, and then that person’s cells begin to produce spike protein, and the immune system will recognize the spike protein and become resistant.
The advantage of RNA vaccine is that it can be produced quickly. It took only a few days for Chinese scientists to publish the new coronavirus gene sequence to the biotech company Moderna’s candidate vaccine for initial testing, and the test began only about two months later. Human volunteers. Several other companies, including pharmaceutical giants Pfizer and Sanofi, are also in the field of RNA vaccines.
Although many scientists are impressed by the potential of RNA vaccines, when COVID-19 appeared on the scene, such vaccines were relatively new. They are not long enough to complete the US Food and Drug Administration (FDA) requirements for their use in human testing.
Making DNA vaccines is another new method of vaccine production. The vaccine introduces genetic instructions directly into the human body to make the target protein. The person’s cells then use these instructions to make RNA that produces the desired protein, thereby stimulating the immune system.
However, getting DNA into human cells is more difficult than getting RNA. Inovio was the first person to start human research in its form, which requires the use of electrical pulses with vaccines to ensure that DNA is ingested. up.
Protein subunit vaccine
Another method of vaccination is to inject people with copies of the actual protein against which you want them to produce antibodies. This is an exploratory method for pertussis, diphtheria and tetanus vaccines.
Dozens of companies are taking this path. Novavax bears the brunt of human trials. It packages the protein in nanoparticles and then injects it with an adjuvant, which is a substance designed to enhance the immune system’s response to proteins.
Generally, it may take ten years or more to develop, test, and license new vaccines, but a coronavirus pandemic may greatly speed up the process because developers are performing work that is usually done in parallel. Even before the candidate vaccine proved effective, the company was expanding its production capacity to make hundreds of millions of doses of drugs that may never be useful. About a dozen vaccines have been tested in humans, and evidence that a particular vaccine is effective or ineffective may be launched by the end of this year.