Xinhua News Agency, Beijing, February 21 (Reporter Li Wen) China recently began to deploy the new crown vaccine sequential booster immunization.
So, is sequential vaccination just "mixing" different brands of vaccines?
In fact, sequential vaccination emphasizes the interval vaccination of different technical routes.
So why sequential vaccination?
Are there similar deployments abroad?
Why Sequential Vaccination
Sequential vaccination refers to the interval vaccination (alternating vaccination) of vaccines of different technical routes.
According to Shao Yiming, a member of the expert group for vaccine research and development of the Joint Prevention and Control Mechanism Scientific Research Team of the State Council of China, at the press conference of the Joint Prevention and Control Mechanism on the 19th, sequential immunization is often used for viruses that are highly variable and difficult to deal with. inoculation.
Wang Huaqing, chief expert of the immunization program at the Chinese Center for Disease Control and Prevention, said that some countries in the Americas, Europe and Southeast Asia have begun to implement sequential booster immunizations.
The European Medicines Agency and the European Centre for Disease Control and Prevention issued a statement in December 2021 saying that multiple studies have shown that mixed vaccination ("mixed") of adenovirus-vectored vaccines and mRNA (messenger ribose nucleic acid) vaccines were able to "generate better antibody levels" and "generate better T-cell immune responses than vaccines using the same technology".
T cells are one of the body's defenses against disease.
The statement said that "mixed fights" can "provide a wider range of vaccination options, especially when a certain vaccine cannot be given for some reason, and it can reduce the impact on vaccine promotion."
Shao Yiming said that the use of sequential booster immunization has two main purposes: first, different vaccines can complement each other's advantages; Side effects can be avoided.
Temporary guide to "fighting"
Based on existing research data, the World Health Organization issued interim guidelines for the "mixed fight" vaccination of the new crown vaccine in December 2021.
This guidance is based on recommendations made by the WHO Strategic Advisory Group of Experts and applies to all COVID-19 vaccines on the WHO's emergency use list.
The guidelines recommend that if the first dose is a viral vector vaccine, subsequent doses of mRNA vaccines can be administered regardless of whether it is a second dose or a booster dose; and vice versa.
If inactivated vaccines are initially administered, viral vector vaccines or mRNA vaccines can be administered later.
As of now, the vaccines that have entered the WHO emergency use list include: AstraZeneca vaccine in the United Kingdom, Johnson & Johnson vaccine, Moderna vaccine and Pfizer vaccine in the United States, Sinopharm vaccine and Sinovac vaccine in China, Covaxin vaccine and Covovax vaccine in India, Nova in the United States Wax vaccine.
Among them, Sinovac, Sinopharm and Covaxin are inactivated vaccines, Johnson & Johnson and AstraZeneca are adenovirus vector vaccines, Moderna and Pfizer are mRNA vaccines, and Novavax vaccine and Covovax are recombinant protein vaccines.
According to the interim guidelines, existing research mainly involves the impact of "mixing" on human immunity.
It is still standard practice to choose the same vaccine as the first dose for the second and third doses, but as research progresses, WHO will reassess the advantages and risks of "mixing".
As more research data comes out, it is not ruled out that the "mixed fight" guidelines will be adjusted.
Many countries approve "mixed fights"
On October 20, 2021, the U.S. Food and Drug Administration revised the emergency use authorization of the new crown vaccine, allowing vaccinators to choose a vaccine booster shot of a different brand of vaccine that was previously vaccinated.
Peter Marks, director of the U.S. Food and Drug Administration's Center for Biologics Evaluation and Research, said the decision to allow the "mixed fight" booster was designed to meet the public's needs as much as possible.
In June 2021, Canada's National Advisory Committee on Immunization announced new rules to allow co-administration of the new crown vaccine in order to further accelerate the progress of vaccination, after studying the results of the mixed vaccination of the new crown vaccine in Spain and the United Kingdom.
People who get the first dose of the AstraZeneca vaccine can choose the same vaccine for the second dose, or the Pfizer or Moderna vaccine.
South Korea, the United Kingdom and other countries have launched clinical trials on sequential vaccination of the new crown vaccine.
The Korean CDC will start a clinical trial of sequential vaccination in May 2021.
The first batch of test subjects is about 500 people who have received one dose of AstraZeneca's vaccine, and the second dose is vaccinated with other new crown vaccines such as Pfizer.
The results of the trial showed that people who received the AstraZeneca and Pfizer vaccines sequentially had 6 times higher levels of neutralizing antibodies than those who received two doses of the AstraZeneca vaccine.
The University of Oxford in the United Kingdom will launch a clinical trial of sequential vaccination of the new crown vaccine in February 2021.
The first phase of the clinical trial used a mix of AstraZeneca's vaccine and Pfizer's vaccine, and the second phase of the trial in April used the Moderna vaccine and the Novavax vaccine.
The test results showed that the level of antibodies produced by volunteers who received the Pfizer vaccine first and then the AstraZeneca vaccine was about five times higher than that of the volunteers who received two doses of the AstraZeneca vaccine. Levels were nine times higher than two doses of the AstraZeneca vaccine.
The AstraZeneca vaccine followed by the Moderna or Novavax vaccines produced higher levels of antibodies than two doses of the AstraZeneca vaccine.