Are the “viruses” produced by RNA vaccines harmful to the body?

Review expert: Gu Haitong, deputy chief physician of respiratory medicine department, Beijing Tongren Hospital, Capital Medical University

Hepatitis B vaccine, polio vaccine, HPV vaccine... In life, we are exposed to a variety of vaccines. Vaccination is the most economical and convenient way to prevent and control infectious diseases. Since the outbreak of the COVID-19 pandemic, almost everyone has received the COVID-19 vaccine. In addition to the inactivated vaccine we are familiar with, there is also an RNA vaccine that often appears in everyone's topic. So, compared with ordinary vaccines, what are the different values ​​of RNA vaccines?

Source: Healthy Chaohu

What are RNA vaccines?

RNA is the carrier of genetic information of biological cells and some viruses, and is mainly divided into messenger RNA (mRNA), transfer RNA (tRNA) and ribosomal RNA (rRNA). RNA is mainly responsible for converting DNA into protein in organisms. If DNA is an encrypted blueprint, then RNA is the engineer who processes the blueprint into a workpiece that can be actually put into use, deciphers (transcribes) the genetic code contained in DNA, and then forms a peptide chain through translation, which is the prototype of protein.

Composition of RNA and DNA

Source: Lianchuan Biotechnology

The RNA vaccine is effective because it utilizes the characteristics of messenger RNA (hereinafter referred to as mRNA). As early as the 1990s, scientists injected in vitro transcribed mRNA into mice and found that it could be expressed in mice, produce related proteins in a dose-dependent manner, and induce immune responses. This is the prototype of the mRNA vaccine. When the mRNA encoding the antigen protein is injected into the human body, it can synthesize the antigen protein in the body, thereby causing the human immune response to fight pathogen infection, which is the mRNA vaccine.

The main function of mRNA is to express genetic information on proteins, and it is a bridge in the process of genetic information transmission. In RNA vaccines, the body is activated to resist the real virus invasion by injecting the virus mRNA.

Source: pexels

What is the difference between RNA vaccines and traditional vaccines?

I believe that everyone has eaten sugar pills when they were young. This white "sugar" is actually the polio vaccine (bOPV). The sugar pill contains a kind of traditional vaccine - live attenuated vaccine, which is a polio virus with greatly reduced toxicity. Traditional inactivated vaccines or attenuated vaccines are to inject dead viruses or viruses with greatly reduced toxicity into the body, so that the body's immune system can recognize them and produce immune responses and antibodies. Antibodies in the body can deal with real viruses.

Source: Baidu Encyclopedia

Traditional vaccines are like giving the body a limited-time weapon (antibody). Only this weapon can defeat the enemy (virus). When the enemy invades, use the weapon and strike hard. However, this weapon is time-limited and has a limited duration, so the weapon needs to be replenished from time to time (the vaccine is injected more than once).

The difference between RNA vaccines and traditional vaccines is that RNA vaccines inject the genetic information mRNA of the virus. The injected mRNA forms some "viruses" through normal translation in the body. This "virus" has the same protein shell as the real virus, allowing the immune system to recognize and remember it. When the real virus invades, the immune system can recognize it and resist it. Moreover, there is no need to worry that this "virus" will be harmful to the body. RNA vaccines only contain fragments of the virus's genetic material and cannot synthesize a complete virus in the body. RNA vaccines are like giving a photo of the virus to the immune system, allowing the immune system to remember what the virus looks like.

mRNA vaccine principle

Source | "mRNA vaccines for infectious diseases: principles, delivery and clinical translation"

Therefore, the difference between traditional vaccines and RNA vaccines is that RNA vaccines allow organisms to produce "viruses" themselves, while traditional vaccines rely on the injection of inactivated or attenuated viruses to allow the body to produce antibodies.

Advantages of RNA vaccines

As an emerging vaccine product in the past two decades, RNA vaccines have incomparable advantages over traditional vaccines.

Source: Sina News

(1) RNA vaccines are safer

RNA vaccines mainly introduce viral mRNA into the body. Due to their own characteristics, they will be automatically destroyed after causing the body to produce viral proteins and will not remain in the body for a long time. The risk of infection for the vaccinated population is very low.

There is also a concern that, as RNA is a genetic material, will it affect its own genome and cause side effects such as mutations? In fact, there is no need to worry at all. The mRNA in the RNA vaccine will not be integrated into the genome, and there will be no risk of infection and mutation. The human genome exists in the cell nucleus, and mRNA mainly plays a role in the cytoplasm. The nuclear membrane of the cell nucleus is like a wall, blocking the mRNA input by the vaccine. In addition, due to the lack of reverse transcriptase, the mRNA input by the vaccine can only be used to translate viral proteins, and cannot be reverse transcribed into DNA that affects our genes.

(2) Vaccines are more effective

Because there are a variety of modification methods that can make mRNA more stable and more efficiently translated; at the same time, the development of delivery methods can enable mRNA to be quickly delivered into cells so that it can function.

(3) RNA vaccines are more effective and require fewer vaccinations

RNA vaccines rely on introducing genetic information fragments of the virus into the body. The immunity generated by this method can last longer than that generated by traditional vaccines, and fewer vaccinations are required to achieve the maximum prevention rate. This is mainly because mRNA controls the cells to produce "viral" proteins with viral characteristics, allowing the immune system to "remember" it. When the real virus attacks, the immune system recognizes the proteins on the virus and can produce highly effective immunity. The principle of traditional vaccines is not like this. It mainly triggers the immune system to produce antibodies by introducing viruses. The effect of antibodies is limited in time, so more traditional vaccinations are required and the effect is not as significant as RNA vaccines.

Source: pexels

(4) Convenience of RNA vaccine production

The development of inactivated vaccines requires cell culture, extraction of viruses from them, and then killing and inactivating the viruses or reducing their toxicity. This is difficult and often takes months or even years. However, the production of RNA vaccines does not require the use of cells. Current in vitro transcription technology only needs to study the RNA fragments of the virus to produce RNA vaccines on a large scale very quickly and cheaply. Compared with the 5-6 month production cycle of traditional vaccines, mRNA vaccines are expected to complete the production and preparation of vaccine samples within 40 days and achieve mass production , so they are expected to better respond to sudden infectious disease outbreaks.

The prospects for RNA vaccines are very good. Recently, the development of mRNA vaccines for cancer, a serious disease, has also begun, and it is expected to be successfully developed before 2030. By then, RNA vaccines will be able to become a major guarantee for consolidating human life and health. Let us look forward to this day and look forward to the future when RNA vaccine technology is fully mature.