Advantages and Disadvantages of Five COVID-19 Vaccines
Advantages and Disadvantages of Five COVID-19 Vaccines. COVID-19 ( new coronavirus) is a new virus, and there are many uncertainties in vaccine development. Although the most optimistic estimate is that the vaccine will be available for emergency use in September this year, the possibility of failure is not small, so eggs cannot be placed in one basket. The simultaneous development of multiple technical routes is a multi-insurance solution. So, what are the technical routes for the development of COVID-19 vaccines? What are their respective advantages and disadvantages?
The development of vaccines generally includes five technical routes: virus inactivated vaccines, nucleic acid vaccines, recombinant protein vaccines, adenovirus vector vaccines, and attenuated influenza virus vector vaccines.
What are the characteristics of these 5 types of vaccines?
Technical route: Inactivated vaccines are the most traditional and classic technical route: culture the new coronavirus in vitro and then inactivate it to make it non-toxic, but the “corpses” of these viruses can still stimulate the body to produce antibodies and make immune cells remember The appearance of living a virus.
The advantages of inactivated vaccines are that the preparation method is simple and fast, and the safety is relatively high. It is the usual means to deal with the transmission of acute diseases. Inactivated vaccines are very common. The commonly used hepatitis B vaccines, inactivated polio vaccines, inactivated Japanese encephalitis vaccines, and DPT vaccines are all inactivated vaccines.
However, inactivated vaccines also have disadvantages, such as large vaccination dose, short immune period, single immune route, etc. The most terrible shortcoming is that it sometimes causes antibody-dependent enhancement effect (ADE), which makes the virus infection worse. This is a serious adverse reaction that can lead to the failure of vaccine development.
Adenovirus vector vaccine
Technical route: Adenovirus vector vaccine uses modified and harmless adenovirus as a carrier, loaded with the S protein gene of the new coronavirus to make an adenovirus vector vaccine to stimulate the body to produce antibodies. The S protein is the key “key” for the new coronavirus to invade human cells. The harmless adenovirus wears the S protein hat and pretends to be fierce, allowing the body to produce immune memory.
The advantages of adenovirus vector vaccines are: safety, high efficiency, and fewer adverse reactions. This vaccine has a successful precedent: Previously, the “recombinant Ebola virus disease vaccine” independently developed by the team of Academician Chen Wei and Tianjin Kangsino Biotechnology Co., Ltd. also used adenovirus as a carrier.
This vaccine also has disadvantages. The development of recombinant virus vector vaccines needs to consider how to overcome “pre-existing immunity”. Take the “recombinant new coronavirus vaccine” that entered clinical trials as an example. This vaccine uses type 5 adenovirus as a carrier, but most people have been infected with type 5 adenovirus during growth, and there may be antibodies that can neutralize the adenovirus vector in the body , Which may attack the vector and reduce the effect of the vaccine. In other words, the safety of the vaccine is high, but the effectiveness may be insufficient.
Nucleic acid vaccine
Technical route: Nucleic acid vaccine includes mRNA vaccine and DNA vaccine. It directly injects the gene, mRNA or DNA encoding S protein into the human body, and uses human cells to synthesize S protein in the human body to stimulate the body to produce antibodies. In layman’s terms, it is equivalent to handing over a detailed virus file to the body’s immune system. The mRNA COVID-19 vaccine in clinical trials of Moderna in the United States is a nucleic acid vaccine.
The advantages of nucleic acid vaccines are: there is no need to synthesize proteins or viruses during development, the process is simple, and the safety is relatively high. Nucleic acid vaccine is a new technology for vaccine research and development that is actively explored all over the world. At present, there is no human-use nucleic acid vaccine on the market.
The technology of this vaccine is too new, and there is no successful precedent, so don’t know where there may be pits in the development process! From an industrial point of view, although the production process itself is not complicated, most countries in the world have a relatively weak foundation in this field, and a stable and controllable mass production supply chain has not yet been formed. So its shortcomings are: there is no successful precedent, most countries cannot produce on a large scale, and it may be difficult to popularize in low-income countries because of the high price.
Recombinant protein vaccine
Technical route: Recombinant protein vaccine, also known as genetic engineering recombinant subunit vaccine. It uses genetic engineering methods to mass-produce the S protein of the new coronavirus that is most likely to be an antigen, and inject it into the human body to stimulate the body to produce antibodies. It is equivalent to not producing a complete virus, but separately producing the key components of many new coronaviruses and handing them to the body’s immune system.
The advantages of recombinant subunit vaccines are: safety, high efficiency, and large-scale production. This route has a successful precedent, and the more successful genetic engineering subunit vaccine is the hepatitis B surface antigen vaccine.
The disadvantage of recombinant subunit vaccines is the need to find a good expression system, which is difficult. Its antigenicity is affected by the selected expression system, so the expression system needs to be carefully selected when preparing the vaccine.
Attenuated influenza virus vector vaccine
Technical route: The attenuated influenza virus vector vaccine uses an attenuated influenza virus vaccine that has been approved for marketing as a carrier, carrying the S protein of the new coronavirus, and co-stimulating the human body to produce antibodies against the two viruses. Simply put, this vaccine is a fusion virus formed by the low-toxicity influenza virus wearing the COVID-19 virus S protein “cap”, which can kill two birds with one stone, and can prevent influenza and COVID-19. When the epidemic of COVID-19 pneumonia overlaps with influenza, its clinical significance is very great. Since the attenuated influenza virus is easy to infect the nasal cavity, this vaccine can be vaccinated only by dripping the nose.
The advantages of the attenuated influenza virus vector vaccine are: one vaccine prevents two diseases, less frequent vaccination, and simple vaccination method.
Live attenuated virus vaccines are a very important type of vaccine. Our usual live attenuated vaccines are: Japanese encephalitis live attenuated vaccine, hepatitis A live attenuated vaccine, measles live attenuated vaccine, rubella attenuated Live virus vaccine, live attenuated varicella vaccine, oral rotavirus live vaccine, etc. But the disadvantage of live attenuated vaccines is that the development process is long.
It should be noted that this technical route does not directly attenuate the new coronavirus into a vaccine, because it requires long-term virus culture and passage attenuation and screening; it uses an attenuated influenza virus vaccine as a carrier. , The disease-causing S protein of the new coronavirus is transferred to the attenuated influenza virus vaccine by bioengineering, so that a lot of virus culture, passage, attenuation and screening time can be saved.