Coronavirus pandemic: know the types of vaccine against covid-19
Photo: Government of São Paulo
Vaccines against covid-19 are being developed at an unprecedented speed, and, in addition to speed, ongoing projects seek to prove the efficacy and safety of new technologies, which in the future may modernize other vaccines already in use in the world.
According to the World Health Organization (WHO), among the nearly 200 vaccine proposals in tests, 44 reached the stage of experimentation in humans, called clinical studies. Of these, a group of 10 projects reached phase three of studies, in which tens of thousands of volunteers are recruited to see if the vaccine is really capable of protecting without causing damage to health.
As it still has a large circulation of the virus, which accelerates research, Brazil has hosted some of these tests with thousands of participants. Vaccines developed by AstraZeneca / Oxford, Sinovac, Janssen and Pfizer / Biontech / Fosun Pharma have received authorization for large-scale experiments in the country.
With techniques already used by science or new ways to induce the immune response, vaccines that have reached the last stage of testing have the same objective: to bring important information to the body that will trigger the production of defenses to the new coronavirus in advance. Agência Brasil explains the main strategies developed by scientists to make vaccines effective and safe.
When the body produces antibodies against a virus, it is stimulated by specific structures that make up these beings. In the case of the coronavirus that causes covid-19, scientists found that protein S, which forms the crown of thorns that gives the virus its name, is the structure that most causes the immune system to produce antibodies. This protein is also fundamental for infection: it is with the small spines formed by protein S that the new coronavirus connects to human cells and initiates the invasion in order to replicate itself.
The director of the Brazilian Society of Immunizations (SBIm), Renato Kfouri, explains that anticipating the body’s contact with protein S is a common strategy for the main ongoing projects. “Vaccines are primarily aimed at inducing antibodies against this S protein. Antibodies are, in general, neutralizing. They are able to neutralize the activity of the virus ”.
Inactivated virus vaccines
Among the ten vaccines that reached phase 3 clinical studies, three proposals developed in China use the technique known as inactivated virus vaccine: that of Sinovac, which is being tested in Brazil in partnership with the Butantan Institute and the government of São Paulo , that of Sinopharm with the Wuhan Institute of Biological Products, and another of Sinopharm with the Beijing Institute of Biological Products.
Boxes with potential Sinovac vaccine against Covid-19 in Beijing
Boxes with potential Sinovac vaccine against Covid-19 in Beijing – Reuters / Rights Reserved
The strategy takes its name because the vaccine contains the dead virus itself, which is technically called inactivated. These vaccines are common in the prevention of several diseases, such as polio, hepatitis A and tetanus, and cause the body to produce defenses from an early and harmless contact with the virus.
“In this technology, the virus is cultivated in the laboratory, and, after having a large quantity, you inactivate, kill the virus in the most popular language, through temperature or chemical substances. It is a whole virus, dead, inactivated, but with these proteins conserved and capable of inducing an immune response ”, explains Kfouri. “The only difficulty is that you need laboratories with a high level of biosafety to handle the live virus, you need to cultivate it, and you have a time to multiply these viruses to then inactivate. These are processes that require a longer time and a maximum level of security for the laboratories, because they will handle viruses with an infectious potential ”.
Viral vector vaccines
To make the body produce antibodies capable of neutralizing protein S, non-replicating viral vector vaccines bring an innovative proposal: the new coronavirus protein is inserted into another virus, modified in the laboratory, to transport it to the body human and not multiply. Once the protein reaches the body, the immune system identifies it and produces structures capable of preventing its action in the future, when the new coronavirus tries to cause infection.
This technology was already being studied to produce vaccines against the Ebola virus and coronavirus that caused outbreaks in previous years, such as SARS-CoV-1, which explains the speed with which it was possible to direct research to SARS-CoV-2. Projects like that of the American Janssen and that of the Chinese CanSino use human adenoviruses to transport protein S to the human body.
The same is proposed by the Gamaleya Epidemiology and Microbiology Research Institute, in Russia, with the difference of using two different types of adenovirus, one in each dose of the vaccine. If proven and registered by the National Health Surveillance Agency (Anvisa), the Russian vaccine must be produced in Brazil by the União Química Group.
The British proposal by the pharmaceutical company AstraZeneca and the University of Oxford uses a chimpanzee adenovirus as a viral vector. This vaccine is being tested in Brazil, and the federal government signed a technology transfer agreement so that the Oswaldo Cruz Foundation can produce it.
a test tube labeled with the vaccine is seen in front of the AstraZeneca logo
Vaccine in AstraZeneca tests – REUTERS / Dado Ruvic / Illustration / Copyright
“The vaccines are from live adenovirus, but they are non-replicating. They remove the proteins responsible for their multiplication from the structure of the adenovirus. These adenoviruses are cold viruses, ”explains Kfouri, who adds that adenoviruses were chosen to carry protein S because they elicit little immune response, allowing the body to concentrate its reaction on the coronavirus protein.
Another technology in tests, never used before in immunization, is that of RNA or DNA vaccines, which insert nucleic acids from the new coronavirus into the human body. So far, only vaccines that use RNA have reached phase three of clinical studies, and their functioning predicts that, upon entering the organism, the nucleic acid of the new coronavirus will cause human cells themselves to produce protein S, which, in turn, instead, it will trigger the production of defenses in the body.
If the efficacy and safety is confirmed, this technology is considered faster for large-scale production, since the vaccine uses synthetic RNA, which dispenses with the cultivation of the virus in the laboratory. The phase 3 studies that seek to confirm the efficacy and safety of RNA vaccines are under the command of the American pharmaceutical company Moderna in partnership with the National Institute of Allergy and Infectious Diseases of the United States, and the research group that brings together the also American company Pfizer , the German Biontech and the Chinese Fosun Pharma.
Kfouri explains that research using RNA vaccines has also moved quickly because they started from studies that were already underway to develop vaccines against other coronaviruses and ebola. “This technology has the potential to be used in many other vaccines, due to its capacity for rapid production. It may be that, if it works, we will migrate other vaccines that we already use today for this platform ”.
Sub-unit protein vaccines
The fourth technology that is under development and has already reached phase 3 studies is that of sub-unit protein vaccines, which propose the injection of protein S and other proteins of the new coronavirus directly into the human body, without the use of viral vectors.
Among the ten vaccines in phase three studies, the only one of this type is that produced by the American pharmaceutical company Novavax.
“They carry bits of the virus, as we do with the flu and HPV vaccine. We take pieces of protein S, protein M, protein E, and make vaccines with these fragments of the virus, which also needs to be cultivated and inactivated, but instead of the entire virus, the vaccine takes viral particles, subunits of the virus ”.
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