The antibody of "mixed vaccination" is 10 times higher? Is "mixed vaccination" necessary to deal with Omicron?

According to media reports, the test results recently released by the China Food and Drug Inspection and Research Institute (hereinafter referred to as "CFDA") showed that after two doses of inactivated vaccine, a sequential booster dose of adenovirus vector COVID-19 vaccine (inhalation form) was given. The neutralizing antibody titer against the pseudovirus of the Omicron variant was only slightly lower than that of the prototype strain, and was 10 times higher than the neutralizing antibody titer after three doses of inactivated vaccine.

A long list of professional terms such as "pseudovirus", "prototype strain", "slightly decreased", etc. bring a lot of reading difficulties.

In short, the "2+1" "mixed" treatment produced antibodies, which were tested on Omicron's pseudovirus and were effective! It may be more effective than the three-shot inactivation.

The question is, why use Omicron's fake virus for experiments? 2+1 mixed attack may be more effective, should mixed attack be enabled?

Why use "fake viruses" for testing? Are the results reliable?

Before the first imported case carrying the Omicron strain entered China, the Omicron variant had not been found in my country.

What should we do if we still want to conduct scientific research even though we don’t have the Omicron strain?

As a national platform, China Inspection has established a technical support platform with independent intellectual property rights very early. Using pseudoviruses, the Omicron pseudovirus is formed through site-directed mutagenesis for preliminary research on vaccine effects.

With pseudovirus technology, Omicron can initially explore the effectiveness of the vaccine before it arrives. The "Technical Guidelines for the Development of New Coronavirus Vaccines for Prevention (Trial)" issued by the National Medical Products Administration specifically mentions that the preliminary immunogenicity exploration can be carried out by the "pseudovirus neutralization method" to measure antibody titers, but the results of this method need to be compared with the results of traditional methods or animal challenge tests, and further verification is required later.

It can be seen that the official guidelines believe that the results of fake viruses are preliminary and still need further verification.

This time, the pseudovirus technology platform concluded that the "mixed" antibody was 10 times higher, but it still needs to be verified by subsequent real Omicron strains and even animal experiments.

As of press time, cases of Omicron infection have occurred in two places in China, and relevant departments are further carrying out follow-up research after obtaining the Omicron strain.

Information shows that the Chinese Center for Disease Control and Prevention, Sinopharm Group, and Sinovac Biotech received the Omicron strain isolated by the University of Hong Kong around December 9, and began virus cultivation and vaccine development.

Is “mixed fighting” really feasible?

Regarding "mixed fighting", the Science and Technology Daily reporter summarized the views from three aspects:

The World Health Organization held a meeting of the Strategic Advisory Group of Experts on Immunization and made corresponding recommendations on the use of polio vaccines, influenza vaccines, malaria vaccines, and new crown vaccines. In terms of booster immunization with new crown vaccines, they recommended the use of homologous vaccines, that is, vaccines with the same technical route; they also discussed the issue of sequential immunization with different technical routes of new crown vaccines, believing that there must be evidence and corresponding research results.

Wang Huaqing, chief expert of the immunization program of the Chinese Center for Disease Control and Prevention, said at a previous press conference of the joint prevention and control mechanism that the current expert advice is to use vaccines produced by the original vaccination company. If the same company cannot meet the supply, vaccines with the same technical route should be selected for vaccination.

Zhang Yuntao, chief scientist of Sinopharm Group China National Biotec Group, told Science and Technology Daily that from the perspective of scientific research and innovation, the country actively supports and encourages the research of "mixed vaccination". China National Biotec Group has carried out the research and development of multiple vaccines including protein recombination, mRNA and other technical routes, and has also carried out research on the effect of "mixed vaccination" between vaccines of different technical routes. If vaccines are "mixed" in a large population, scientific laws need to be followed.

What research should be done before a “mixed fight”?

Relevant experts said that based on current policies and regulations, the vaccine for mixed injection must be a vaccine that has been approved for marketing or has obtained emergency marketing authorization. The effect of mixed injection should be evaluated on sensitive animals and should not be limited to the results of neutralizing antibody titers. The safety of mixed injection must be evaluated and verified on a qualified GLP (Good Laboratory Practice) platform.

Therefore, whether to mix vaccines or not still needs further scientific research to verify. Wang Huaqing also said earlier that "we will conduct demonstrations based on the results of sequential immunization research conducted by relevant companies and put forward relevant suggestions."

Vaccine products have strict regulations in terms of marketing, use strategies, and indications, which must be strictly implemented according to the requirements of the State Food and Drug Administration when approving the application. If "mixed vaccination" is implemented, it is necessary to submit materials, apply, and be approved for marketing after review and approval, or obtain emergency use permission from relevant departments.

Is it necessary to "mix and match" to deal with Omicron?

In response to the mutant strains, my country's vaccine research and development units have been continuously tracking, intervening in advance, and conducting research.

Xu Wenbo, director of the Institute of Viral Disease Prevention and Control of the Chinese Center for Disease Control and Prevention, stated at a press conference of the State Council's Joint Prevention and Control Mechanism that China has completed preliminary technical reserves and research on multiple technical routes including inactivated vaccines, protein vaccines, and vector vaccines for the Omicron variant, and some companies have already started relevant preliminary designs.

"When a new large-scale epidemic variant emerges, we will activate our mature and complete technical system, namely the emergency research and development and production system for emerging infectious diseases, and quickly complete the development of a new inactivated vaccine to respond to the variant." Zhang Yuntao told Science and Technology Daily that all research work before clinical trials can be completed in about two months.

Whether Omicron's enhanced ability to escape the immune system will reduce the effectiveness of existing vaccines remains to be further confirmed; once it escapes, which strategy to adopt also needs further evaluation.

At present, the safety of "mixed shots" still needs to be further verified, and the development cycle of new crown vaccines specifically for Omicron is relatively short. Is it "mixed shots" or vaccination with new vaccines? The relevant departments will make the judgment based on "maximum protection at the minimum cost".

Source: Science and Technology Daily

◎ Science and Technology Daily reporter Zhang Jiaxing

Editor: Wang Yu

Review: Yue Liang

Final review: Liu Haiying