COVID-19 Vaccine: Why mRNA vaccines are preferred?

COVID-19 Vaccine: Why mRNA vaccines are preferred?

COVID-19 Vaccine: Why mRNA vaccines are preferred? On December 2nd, the UK took the lead in approving Pfizer’s vaccine, and the vaccine began on the 8th. Today, the vaccine has also been approved in the United States, and national vaccination is expected to begin on the 15th. On the 17th of next week, the US FDA is very likely to approve Moderna’s mRNA vaccine, and it is possible to start vaccination on the 22nd. Except that these two viruses first completed the Phase III clinical randomized study, what factors made the world look at mRNA vaccines in awe?

Because retrovirus has the longest gene conversion rate and maintenance time, it is a pity that it will integrate into the DNA of the human host. Some scholars worry about the possibility of cancer. At present, this gene transformation method has been rarely used in cancer treatment.

Adenovirus does not integrate into human DNA, but it is toxic to cells to a certain extent and can cause the body to become immune to adenovirus vectors. This may explain the side effects of the AstraZeneca COVID-19 adenovirus vector vaccine, and the change in the effective rate of the initial dose (the high dose of the first vaccination may stimulate a stronger immune response against the adenovirus vector and affect the second vaccination. The result. Therefore, it is better to use a lower dose for the first time).

The nanotechnology liposome itself has less impact on the immune system, and general mRNA will not be reverse-transcribed and integrated into human DNA, but it temporarily expresses a large number of proteins to be delivered in human cells (such as COVID-19 spike protein, Activate the immune response, and then gradually fade), the best safety. However, I used a DNA plasmid at the time; because DNA is relatively stable. At that time, everyone knew that RNA extraction and preservation were very tricky, and there was no precedent for successful mRNA gene transformation.

The lipid carrier-mediated gene delivery of the COVID-19 spike protein mRNA as the main body avoids errors in the DNA transcription process and potential side effects during the transcription process, allowing the spike protein to be efficiently expressed in human cells in a short period of time and activate the body The immune response, which is more effective than natural infection to produce specific anti-viral antibodies and immune killer cells.

Although gene expression is short-lived, activated B cells and T cells have their own memory and can eliminate or inhibit the virus for a “long time”. At the same time, this mRNA will not be reverse transcribed into DNA, and it will not be integrated into the host DNA, which is safe and reliable.

For decades, the method of mRNA gene delivery has been the dream of scientists. The founding partner of Moderna, the inventor of mRNA technology, and Hungarian-American scientist Katalin Kariko has worked on a cold bench for 40 years, and originally planned to establish Moderna to engage in mRNA cancer vaccines.

As a result, the COVID-19 epidemic broke out. When Chinese scientists announced the gene sequence of COVID-19 (including the spinous protein) on January 10 this year, researchers in the United States and Germany changed hands and wanted to plant flowers without blooming. Chengyin Liu Liu, very lucky, this spike protein proved to be a good immunogen for COVID-19, and the COVID-19 mRNA vaccine is here! This is an important breakthrough in human science and technology and the result of the joint efforts of scientists from all over the world!

In contrast, inactivated virus vaccine is a more mature method, and the annual flu vaccine uses this traditional method. Its research and development success rate is high, so it is widely used. However, because the heat is not easy to control during the inactivation process, it brings certain difficulties to quality control. Production capacity is therefore subject to certain restrictions. At the same time, the added chemicals will also bring some side effects.

Generally, the effective rate of inactivated influenza vaccine is between 50% and 70%. At present, the domestically-made COVID-19 vaccine with inactivated vaccine as the main body and adenovirus vector has been reported in the early stage of toxicity and antibody positive rate. Volunteers can tolerate mild to moderate side effects, and antibodies are also positive after injection.

However, a positive antibody does not guarantee that it has sufficient protection. The effective rate must be obtained in a three-phase randomized study with a control group. As the epidemic situation in China is well controlled, corresponding research must be conducted in other countries with high incidence.

On December 9, the UAE Ministry of Health approved and reported the results of the Phase III clinical study of China’s SINOPHARM inactivated vaccine, which showed an effective rate of 86%, no serious side effects, and can significantly reduce the occurrence of serious cases. Details have not yet been announced. The advantages of inactivated vaccines and adenovirus vector vaccines are that they are less affected by temperature and are easy to store and transport, making them more suitable for developing countries.

Due to potential advantages such as improved vaccine efficiency and productivity brought about by technological innovation and high antigen expression and reduced side effects, when the effective rate of the mRNA COVID-19 vaccine reached 95%, the industry unanimously hailed this major breakthrough.

More importantly, there are almost no severely ill patients among the vaccine recipients. Many people think that this is the coming of God’s grace! Developed countries such as the United States and the United Kingdom have pre-ordered the products of these two companies. China’s Fosun has also signed a cooperation agreement with Pfizer and has completed the first phase of clinical trials. It is expected that related phase 2 (non-randomized) clinical studies will be launched in China soon to obtain approval from the Chinese FDA for marketing.

Although the US medical insurance and the government will pay for the vaccination, another difficulty that is currently facing is that more than 37% of the American people are uneasy about the vaccination and are not ready to vaccinate immediately. In this regard, the three former presidents of the United States, Bush, Clinton, and Obama said that they will be vaccinated as soon as possible under the observation of the media, as a platform for vaccine safety.

Because the vaccine is for normal people, it is not a “medicine”, it is not a cure for the patient, but a disease prevention. At the same time, for the COVID-19 vaccine, the population to be vaccinated is billions of healthy people, including children. Therefore, its safety must be much stricter than “medicine”. Therefore, if time is not urgent, all new vaccines should wait for long-term (more than 2 years) data before final approval.

But in the face of a severe epidemic, this is irrational. Regulations that allow emergency use are designed for this situation. At present, the US FDA’s requirement is that after the last patient is enrolled in the Phase III clinical study, observe at least another 2 months to ensure that there are no serious acute side effects. Moreover, regulatory agencies must strictly control the use of these new vaccines from the beginning.

The initial use of these vaccines is limited to those who need them most-doctors, nurses, other health care workers, and elderly people in nursing homes. Regulators also need to continue to closely monitor the side effects of vaccines already on the market (the so-called Phase IV clinical study). With the accumulation of data in the first two months of next year, the scope of vaccinators will be further expanded.

(soruce:weibo)

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