China has made a major breakthrough in COVID-19 vaccine. The vaccine was approved by the State Administration of Pharmaceutical Products on June 9, 2009 and entered the clinical trial. This vaccine is an mRNA vaccine, not a nucleic acid vaccine. This vaccine has realized mRNA vaccine in China? Zero? This breakthrough also marks that China's research and development level and regulatory capacity of nucleic acid vaccines rank among the top in the world. The vaccine has the advantages of safety, effectiveness and short development cycle. MRNA vaccine is a kind of vaccine that synthesizes the mRNA sequence encoding a specific antigen in vitro, and then delivers it to the body to express the corresponding antigen protein, which causes humoral and cellular immune responses by simulating virus infection, thus producing immune protection. Both MRNA vaccine and DNA vaccine belong to nucleic acid vaccine. Nucleic acid vaccine is the third generation vaccine developed on the basis of the first generation attenuated/inactivated vaccine and the second generation subunit vaccine. MRNA vaccine maintains the advantage of DNA vaccine in expressing intracellular antigen, overcomes the shortcomings of low immunogenicity and nonspecific immunity to carriers, and there is no risk of integration into host DNA. It can be said that mRNA vaccine is a vaccine with great development potential. There are two main types of mRNA vaccines, non-replicating and self-amplifying. Compared with non-replicating mRNA, self-amplifying mRNA can not only encode antigens, but also have sequences similar to virus replication process, so it can replicate in cells and improve protein expression.
Three advantages of vaccine: 1. Safety: mRNA vaccine is non-integrated and will not be integrated into the genome, thus avoiding the risk of gene mutation; It can be degraded by physiological metabolism, or its half-life in vivo can be adjusted by sequence modification and delivery vector. 2. Effective: mRNA vaccine can induce humoral immunity and cellular immunity. It is safer to induce two types of immune response when we don't fully understand the immune response mechanism in novel coronavirus. 3. The research and development cycle is short: it takes several generations for live attenuated vaccine to screen out suitable virus strains, and it takes time for inactivated vaccine to go through the process of virus culture and repeated inactivation, and protein subunit vaccine needs to be produced, isolated and purified in vitro. However, mRNA vaccine only needs to construct genetic material in vitro and then inject it into human body, and human cells produce immunogenic proteins, so it has the potential of rapid production and low cost, and is one of the important strategies to deal with sudden infectious diseases.