How to choose between single-shot and double-shot COVID-19 vaccines? Here comes the authoritative response!

At present, the overseas epidemic is still severe, while the domestic epidemic has been effectively controlled. When it comes to the choice of COVID-19 vaccine, many people have encountered the "trouble of choice": should they get vaccinated? Which type of vaccine is better? How to choose between single injection and double injection? In this regard, Xinhua News Agency reporters interviewed relevant competent departments and authoritative experts in the industry.

At present, my country has 4 new coronavirus vaccines that have been conditionally approved for marketing by the National Medical Products Administration. According to the technical route, there are two categories: one is inactivated vaccines, including 3 inactivated vaccines produced by Sinopharm Beijing, Sinopharm Wuhan, and Beijing Sinovac Biotech; the other is adenovirus vector vaccines, which is the type 5 adenovirus vector vaccine produced by Tianjin CanSino Biologics.

Which one is better?

The relevant competent departments of the National Health Commission stated that no matter what technical route is adopted, as long as the vaccine has been formally approved for conditional marketing by the country, its safety and effectiveness are supported by certain data, and the potential benefits or known benefits are greater than the potential risks or known risks, and the public can use it with confidence.

According to industry experts, the two technical routes of the new coronavirus vaccine have their own characteristics.

Shao Yiming, a researcher at the Chinese Center for Disease Control and Prevention and an advisor to the World Health Organization's Vaccine Development Committee, said that inactivated vaccines are made by killing the coronavirus after it has been cultured and amplified, and then injecting the inactivated virus particles into the human body to induce an immune response. Because inactivation destroys some protein antigens on the surface of the virus, the immunogenicity of the vaccine is lower than that of the live virus, and double or triple injections are often used. The first injection induces memory cells, and the second injection exponentially enhances the overall immune response by stimulating the memory response.

Wang Junzhi, deputy leader of the vaccine research and development team of the scientific research team and academician of the Chinese Academy of Engineering, said that the main feature of inactivated vaccines is that the vaccine ingredients are close to the natural virus structure, usually the immune response is strong, and it has good safety. This vaccine is relatively stable and can be stored for two to three years under storage and transportation conditions of 2 to 8 degrees Celsius.

The adenovirus vector vaccine is like a car carrying the "new coronavirus antigen gene" cargo. After being delivered into human cells, the "new coronavirus antigen gene" can neither replicate itself nor cause disease, but it can express the protein antigen of the new coronavirus and stimulate the human immune system to produce antibodies.

Wang Junzhi introduced that the adenovirus vector vaccine independently developed by my country uses "type 5 adenovirus" as a vector and introduces the "new coronavirus antigen gene", which can not only induce the production of good neutralizing antibodies, but also induce enhanced cellular immunity. The currently approved immunization procedure is a single injection.

So, how to choose between single needle and double needle?

Shao Yiming said that for people who have temporary or urgent tasks to go to the epidemic area but do not have enough time to wait, it is more suitable to be injected with a single-dose adenovirus vector vaccine.

In addition, the single-dose adenovirus vector vaccine has the following advantages: First, a single injection completes the entire course of immunization, avoiding immune loss caused by long distances, busy work, or lack of vaccines, thus ensuring a high vaccination rate; second, the overall cost of a single injection is lower, and the cost-effectiveness ratio is higher. Third, in the current situation of insufficient global vaccine production capacity, a single-dose vaccine can vaccinate twice as many people, increasing the accessibility of vaccines.

However, every advantage has its disadvantages. Shao Yiming pointed out that the intensity of the immune response induced by a single-shot adenovirus vector vaccine is generally weaker than that of a two-shot vaccine. Because when this type of vaccine is administered again, the human body mainly produces a memory response to the "car" - the adenovirus vector, rather than the "cargo" - the "new coronavirus antigen gene." This type of single-shot vaccine is fine for preventing early epidemic viruses, but when it is replaced with a later mutated virus, the protection efficiency will mostly decrease. Therefore, when choosing a vaccine, it is necessary to make a comprehensive judgment and scientific decision based on the specific situation of the population to be protected and the latest monitoring data of the local epidemic virus.

Source: Xinhua Viewpoint, Science and Technology Daily

Editor: Wang Yu

Reviewer: Guan Jingjing

Final judge: He Yi