COVID-19 swept the world, and China spent two months trying to control the epidemic, but this does not mean the end.

At present, five COVID-19 vaccines have entered global clinical trials. Usually, vaccines need to go through three stages of clinical trials before registration and marketing. The goal and significance of each stage are different. According to the design of R&D, different schemes require different time.

1

Phase I clinical trial

The key point is to observe the safety of use, mainly through a small number of susceptible healthy volunteers as subjects, to determine the human body's tolerance to different doses of vaccines and understand its preliminary safety. Generally, the number of people is relatively small, ranging from tens to 100.

2

Phase II clinical trial

The purpose of expanding the sample size and target population is to further confirm the preliminary effectiveness and safety of the vaccine in the population and determine the immunization program and dose. The average number of subjects is several hundred. It should be pointed out that phase I and phase II clinical trials are conducted by healthy volunteers, and it takes about several months according to different immunization procedures and different schemes.

three

Three stages of clinical trials

The required sample size is larger. For general infectious diseases, it is generally necessary to observe an epidemic cycle to determine its protection rate for susceptible people. Its scale is thousands, some even tens of thousands.

It is necessary to produce qualified vaccine samples and prove their safety and effectiveness in animal experiments before they can enter clinical trials. What really determines the effectiveness of the vaccine is the third-phase clinical trial, and the final result is the scientific basis for the vaccine to be approved for marketing.

There are three kinds of COVID-19 vaccine * * * that have entered the first and second joint clinical trials in China, namely, adenovirus vector vaccine developed by Chen Wei's team of the Academy of Military Sciences, inactivated vaccine developed by China Institute of Biological Products of Sinopharm Group and inactivated vaccine developed by Beijing Kexing Zhongwei Biotechnology Co., Ltd. In addition, recombinant genetic engineering vaccine, influenza virus vector vaccine and nucleic acid vaccine are also under development.

How does COVID-19 vaccine make people immune?

Adenovirus vector vaccine

inactivated vaccine

It is a vaccine that kills pathogenic microorganisms but still maintains its immunogenicity. It has the advantages of mature production technology, controllable quality standard and wide protection range. Inactivated vaccine does not need to find the key components that can produce immunity in pathogens, so it is easy to achieve. If the adverse reactions are not too great, this is a simple and low-cost vaccine technology. Inactivated vaccines also need to cultivate pathogens, purify and add stabilizers. The yield is average, because the effect is slightly poor, the dose usually needs to be larger than the same live vaccine.

Recombinant genetic engineering vaccine

Genetic engineering vaccine is a product obtained by cloning a gene fragment encoded by a protective antigen of a pathogen into an expression vector for transfection of cells, eukaryotes and prokaryotes, or deletion of virulence-related genes of the pathogen to make it a gene deletion vaccine without virulence-related genes. This technology has been used in hepatitis B vaccine, cervical cancer vaccine and hepatitis E vaccine for 30 years, 14 years and 8 years. S protein is a synaptic protein on the surface of COVID-19. At present, Jinhai team of School of Life Sciences of Tianjin University uses Saccharomyces cerevisiae to produce S-component protein vaccine, and Longkema Company, a subsidiary of Chongqing zhifei, uses CHO cells to produce S-component protein vaccine.

Influenza virus vector vaccine

The influenza virus vector technology of COVID-19 vaccine is to transfer the S protein gene into the gene carrying influenza virus, so that the S protein grows on the surface carrying influenza virus, and the human body can be immune to this influenza virus or to 20 19 coronavirus, which can kill two birds with one stone.

Nucleic acid vaccine

At present, microbes in Shanghai are developing mRNA vaccine, and Xu Jianqing's team in Shanghai Public Health Clinical Center is developing DNA vaccine. DNA and mRNA are both nucleic acids, and vaccines based on these two technologies are both nucleic acid vaccines. Nucleic acid is the genetic material of life, and the part of nucleic acid with information encoding various components of life is also called gene. DNA is the original gene and mRNA is the replication gene. MRNA vaccine is to directly inject genes into human body, so that human cells can use this foreign gene to synthesize vaccine components. Compared with non-nucleic acid vaccine, nucleic acid vaccine has a prominent advantage, that is, it can be replicated and its output is amazing.

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