Text | Synthesized from the official website of the National Health Commission, Science and Technology Daily, etc
Have you been given a covid-19 vaccine booster?
If you haven't had time to fight yet, now you have more options.
On February 19, the joint prevention and control mechanism of the State Council press conference introduced that the National Health Commission has begun to deploy a sequential strengthening of immunization.
What exactly is sequential booster immunization? Why promote sequential vaccination? How to vaccinate specifically, what are the advantages and safety of the new regimen compared to the previous vaccination strategy? Who can go and fight?
▲On January 6, at the covid-19 vaccination site of Anhui Agricultural University, medical staff vaccinated teachers and students with a reinforced injection of the new crown vaccine. Photo by Xinhua News Agency reporter Huang Bohan
What is "sequential intensification of immunization"?
Sequential inoculation is relative to homologous inoculation.
Previously, the mainland has been implementing a homologous booster immunization strategy, that is, the booster needle should choose the same technical route of the new crown vaccine for vaccination, for example, if the new crown vaccine has previously completed two doses of inactivation process, the subsequent use of inactivated vaccine for enhanced vaccination.
The so-called sequential vaccination, which is commonly referred to as the vaccine "mixed beating", refers to the same vaccine of different technical routes of interval vaccination (alternating vaccination), including sequential basic immunization and sequential enhanced immunization.
Therefore, a sequential booster immunization programme means that if two doses of COVID-19 vaccination has previously been completed, any other non-inactivated covid-19 vaccine can be switched to a subsequent booster injection.
Wang Huaqing, chief expert of the immunization program of the Chinese Center for Disease Control and Prevention, said that when it came to sequential immunization before, it was mainly the polio vaccine we applied, that is, polio sugar pills, and the whole process of vaccination required 4 doses. The current vaccination is also completed in 4 doses, but the first two doses are given against inactivated trivalent polio vaccine and the last two doses are given with bivalent live attenuated vaccine.
Judging from the practice of other countries and regions, in response to the new crown pneumonia epidemic, some countries in the Americas, Europe and Southeast Asia have begun to implement a sequential intensification of immunization.
The World Health Organization also supports flexible cognate vaccines and heterologous vaccination programmes. On 16 December 2021, the World Health Organization (WHO) issued the Interim Guidelines for Heterologous Enhancement of COVID-19 Vaccines, which recommends that if the first dose is given against the Messenger Ribonucleic Acid (mRNA) vaccine, the booster needle can be vaccinated against the viral vector; and vice versa. If inactivated vaccine is initially given, follow-up vaccination with viral vector vaccine or mRNA vaccine may be given.
Why "mix-up"?
Why deploy sequential vaccination now?
"Sequential immunization is a process of continuous improvement of immune strategies and a decision based on scientific evidence." Wang Huaqing said that in the process of formulating a sequential immunization strategy, on the one hand, its protective effect is considered, on the other hand, like the polio vaccine using a sequential immunization procedure, it is more important to consider further reducing the risk of serious adverse reactions.
At present, the Omikerong strain has also become the dominant strain of imported and local epidemics outside the mainland, with stronger transmission and faster transmission speed, and the risk of overseas imported epidemics and local epidemics on the mainland has increased significantly.
Shao Yiming, a member of the vaccine research and development expert group of the scientific research group of the joint prevention and control mechanism of the State Council, believes that according to the previous experience in the prevention and control of infectious diseases, a single vaccine can deal with conventional viruses, but for the cunning virus that is good at mutation, different vaccines can be implemented "joint operations".
He said that the use of sequential immunization mainly has two purposes: one is that different vaccines can complement each other's advantages, and the other is that for some people, side reactions can be reduced, due to different personal constitutions, there may be more side reactions to a certain vaccine, in this case, you can change a vaccine, so as to avoid side reactions.
Safe or not, how effective is it?
It is understood that there are currently two combination options for sequential booster immunization:
First, inactivated vaccine (Vero cells) 2 doses of basal immunity + recombinant protein vaccine (CHO cells) 1 dose of boosted immunity;
The second is inactivated vaccine (Vero cells) 2 doses of basal immunity + 1 dose of adenovirus vector vaccine to strengthen immunity.
So, is the safety and effectiveness of the two new schemes guaranteed?
"Security is assured." Shao Yiming introduced that the inactivated vaccine in the mainland has confirmed its safety in the use of billions of doses, and the other two vaccines have fully proved its safety in the use of tens of millions and hundreds of millions of doses. In terms of side effects, the side effects of sequential vaccination and the use of vaccines alone are the same or even smaller, and no other side effects have been observed.
Moreover, from the international level, the World Health Organization, as well as some European and American countries have carried out a large number of sequential vaccination trials, including inactivated vaccines on the mainland with adenovirus vector vaccines, protein vaccines, mRNA vaccines, there are also inverted, on the basis of mRNA vaccines and other vaccines, the results of these studies are safe.
▲The vaccinated personnel are waiting in the observation area. Photo by Ju Huanzong, Xinhua News Agency
In terms of effectiveness, the country has organized relevant research work in the early stage, including the sequential strengthening of the adenovirus vector vaccine as a heterologous on the basis of inactivated vaccines, and the sequential strengthening of heterologous protein vaccines, the results of immunogenicity are very good, neutralizing antibodies are 100% yang transfer, and the titer of neutralizing antibodies can also be raised higher, which can play a complementary role.
For example, on November 23, 2021, a study published in Cell Research by Zhang Wenhong, director of the Department of Infectious Diseases at Huashan Hospital affiliated to Fudan University, showed that two inactivated vaccines plus one dose of recombinant protein subunit vaccine boosters can significantly enhance the neutralizing antibody titer against the new crown virus and mutant strains.
Who can choose sequential vaccination?
Under the deployment of the new sequential booster immunization, not all people are suitable for sequential immunization.
Wang Huaqing introduced that the object of this sequential immunization has 4 conditions: first, it must be a person over 18 years old; second, it is necessary to complete 2 doses of inactivated vaccination, and these 2 doses are the new coronavirus inactivated vaccine of Sinopharm Zhongsheng Beijing Company, Beijing Kexing Company, and Sinopharm Zhongsheng Wuhan Company; third, to complete 2 doses of vaccination, and the vaccination interval cannot be less than 6 months; fourth, there has been no enhanced immunization, that is, the 3rd injection has not been played.
A previous press conference on the joint prevention and control mechanism of the State Council revealed that as of February 7, nearly 460 million people had completed enhanced immunization on the mainland. That is, these populations that have completed boosted immunization do not need to be vaccinated repeatedly.
In addition, people who have completed full immunization using vaccines other than the three inactivated vaccines cannot be immunized sequentially at this stage.