What is the protection rate and safety of the two Chinese vaccines under the spotlight, Kexing and Sinopharm?
At present, more than 100 million people have been vaccinated in China. And Gao Fu, director of the Chinese Center for Disease Control and Prevention, recently said that the domestic new crown vaccine does not have a high protective power, causing public concern. What is the protection rate and safety of the two Chinese vaccines under the spotlight, Kexing and Sinopharm? Dr. Xiaoxu Lin, a U.S. virologist and former laboratory director of the Department of Virus at the U.S. Army Research Institute, answers 3 questions about Chinese vaccines. The following is the essence of Lin Xiaoxu’s interview.
Q1. Why are Kexing and Sinopharm not on 80% protection rate?
According to the official data released by the Chinese Communist Party, the overall protection efficacy of Kexing vaccine is 50.65%, the overall protection efficacy of Sinopharm Zhongsheng (Beijing) vaccine is 79.3%, and the overall protection efficacy of Sinopharm Zhongsheng (Wuhan) vaccine is 72.5%. However, on April 10, Gao Fu, director of the Chinese Center for Disease Control and Prevention (CDC), suggested that the protective efficacy of Chinese vaccines is not high, and considered allowing the population to mix vaccines of different technologies and called attention to mRNA vaccines.
The reason for the low vaccine protection in China is related to the type of vaccine.
Both Kexing vaccine and GMP vaccine are inactivated vaccines, which are made by killing the intact strain of the virus.
Because it uses intact virus particles, it contains various proteins expressed by the virus. However, after the virus is killed, its conformation will change somewhat. It is like a person, who has various expressions and movements when alive, and after death, although it still looks like the same person, it is lifeless and is limp and collapsed. And the human immune system is very smart, it will not react too much to a dead virus. Therefore, inactivated vaccines do not activate too strong an immune response; the activation of killer T cells, even less. (Recommended reading: Is your immunity stronger than the vaccine?)
That is, the protection rate of inactivated vaccines is, as a rule, not particularly high.
The international standard for the protection rate of inactivated or attenuated vaccines is set at about 50%. For example, the protection rate of influenza vaccine, whether inactivated or attenuated, is between 50% and 70%, which is lower than the 90% protection rate of mRNA vaccines Pfizer and Modena.
Q2. Are there any safety risks of inactivated vaccines?
Inactivated vaccines have two main risks.
● The manufacturing process of inactivated vaccines, which is exposed to huge safety risks
To manufacture inactivated vaccines, the virus has to be cultured first and then inactivated. Then the first challenge is: whether the inactivation is complete and whether there is any surviving virus left. Therefore, every step of the process, from culturing the virus, inactivation to testing, requires very strict monitoring.
If virus inactivation is not complete during the production process, then a healthy person can be infected by the vaccination. The new coronavirus is highly transmissible, lethal, and can attack many organs in the human body, so the danger is much higher than SARS and Middle East Respiratory Syndrome, and the damage brought by the infection is high.
● Antibody-dependent enhancement effect (ADE)
Antibody-dependent enhancement effect, or ADE for short, is that certain antibodies produced by the body after vaccination, instead of resisting the virus, help the virus to invade human cells better.
This is a problem often faced by inactivated vaccines. The SARS and Middle East Respiratory Syndrome outbreaks of the same coronavirus have not been able to develop a successful vaccine for many years, and it is in this regard that no breakthrough can be made, because the percentage of such side effects occurring is still relatively high.
In fact, the vaccine companies have not released too many details about what side effects the Chinese vaccine will produce, and there are no official reports about the side effects, so at present, we can only use the adverse reaction reports from Hong Kong or other countries that have injected Kexing and GMP vaccines as a reference.
It is reasonable to say that more than 100 million people have been vaccinated in China, so there should be a lot of relevant data. I hope that the Chinese government will publish detailed and detailed data, as other countries have done, so that the public can fully understand the risks after vaccination.
At the same time, it is suggested that the Chinese government should also establish a system for reporting adverse reactions to vaccines, as the CDC has done in the United States, so that the public can be informed of any adverse reactions in a timely manner, and the outside world can also inquire and be informed of the specific situation of adverse reactions in a timely manner.
Q3. What is the reason why the Phase III data of Chinese vaccines have not been published in international journals so far?
Why have the Phase III clinical data of Kexing and Sinopharm not been published in international journals?
One possible reason is that the clinical data of Kexing vaccine in different countries are too different. The protection rate of Kexing vaccine in Turkey is more satisfactory, reaching 91%; in Indonesia, the protection rate is 65%; and in Brazil, it is only 50.3%. It is difficult to find a balance value as the high one can reach 91% and the low one only 50.3%.
In addition, the clinical trials of Kexing and Sinopharm mainly focus on people aged 16 to 60 years old, and there is a lack of data on elders over 60 years old, then there is no clinical data to prove whether the vaccine is safe for elders over 60 years old. However, elderly people happen to be listed as the second priority group for vaccination in many countries (health care workers are the first priority) because they are more likely to become seriously ill when infected and need to be protected in a focused manner. The lack of data in this area raises concerns about the safety of vaccination for people over 60 years of age and makes it difficult to provide a scientific basis that would enable widespread administration.
There is also a doubt as to whether there have been cases of ADE effects.
One of the informed consent forms that one has to sign before getting the vaccine in China, one of the consent forms, very clearly warns the vaccinated person of the ADE effect as a very major side effect. The common side effects noted for other vaccines internationally are mostly common reactions such as pain at the injection site, fever or redness on the body. There are also individual vaccine instructions that mention the possibility of ADE, but they are not ranked very low as an important possibility.
Informed consent form for Chinese inactivated vaccines.
The informed consent form for the Chinese vaccine states that no antibody-dependent enhancement effect was observed in large animal tests, but “the possibility of exacerbation of disease after vaccination with novel coronavirus infection cannot be ruled out”. This statement seems like a responsible approach to inform the public about the risks, but to put it another way, have they already found such cases in clinical trials? After all, the ADE effect is the most worrisome and serious side effect of the vaccine development process. Many vaccine developments have failed because of ADE effects.
Objectively speaking, unsuccessful vaccine development is a normal scientific phenomenon. Over the past decade or so, pharmaceutical companies have designed many vaccines for SARS and Middle East Respiratory Syndrome, but they all failed. I hope that there will not be too many political factors involved in scientific experiments, in order to bring safety to the public.
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