How effective are Omicron-specific booster shots in combating COVID-19? Know report

0
Omicron-specific booster shots

Colombia: On August 31, 2022, the Food and Drug Administration authorized the use of updated COVID-19 booster shots specifically designed to combat the two most recent and infectious Omicron subvariants, ba.4 and ba.5. Following the FDA’s emergency use authorization, the Centers for Disease Control and Prevention is expected to begin vaccinating people within the next few days. One of the new booster shots is produced by Moderna and the other by Pfizer-BioNtech, as more than 450 people are still dying from COVID-19 in the US every day. As of August 31, 2022, only 48.5% of booster-eligible people in the US have received their first booster shot, and only 34% of those eligible have had their second shot.

These low numbers may be partly due to people waiting for newer versions of vaccines to provide better protection. But booster shots have proved to be an essential layer of protection against COVID-19. Prakash Nagarkatti and Mitzi Nagarkatti are immunologists who study infectious disorders and explore how vaccines activate different aspects of the immune system to fight infection. They look at how the updated booster shots train the immune system and how protective they can be against COVID-19.

  1. What’s different about the updated booster shots? The new authorized shots are the first updates to the original COVID-19 vaccines that were introduced in late 2020. They use the same mRNA technology as the original vaccines. The key difference between the original COVID-19 shots and the new “bicombinant” version is that the latter contains a mixture of mRNAs that spike both the original SARS-CoV-2 virus and the more recent Omicron subvariants, ba.4 and ba.5. Encodes proteins. , As of the end of August 2022, the ba.4 and ba.5 Omicron subvariants are dominant worldwide. In the US, currently, 89% of COVID-19 infections are caused by BA.5 and 11% by BA.4. The original vaccine’s failure to prevent re-infection and long-term protective immunity against virus strains led to the need for better vaccines.
  2. How does a bivalent vaccine activate the immune response? In a true COVID-19 infection, the SARS-CoV-2 virus uses its protruding spike protein to bind to and enter human cells. The spike protein activates the production of the so-called neutralizing antibody, which binds to the spike protein and prevents the virus from invading other cells. But when the virus mutates, as we know it, the antibodies that were Previously generated in response to a virus, the newly mutated spike no longer binds effectively to the protein. In this regard, the SARS-CoV-2 virus acts like a chameleon and evades the immune system by changing its body configuration. This is why the antibodies produced have become less effective in preventing infection by the newer variants over time. The concept of bivalent vaccines aimed at protecting against two different strains of a virus is not new. For example, Cervix is ​​an FDA-approved bivalent vaccine that provides protection against two different types of human papillomaviruses that cause cancer.
  3. How protective will the new shots be against infection? There are no human studies yet on the efficacy of the new bivalent vaccine in preventing reinfection and providing long-term immune protection. However, in human clinical trials and laboratory studies, both Pfizer-BioNTech and Moderna found that the initial version of their bivalent vaccine, directed against the original SARS-Cov-2 virus and the earlier Omicron strain, BA.1, did not work in the original. Provided longer protection against both strain and BA.1 version. In addition, the companies reported that the same initial combination produced a significant antibody response against the latest Omicron subvariants, ba.4 and ba.5, although this antibody response was lower than against subvariant ba.1. Based on these results, in spring 2022 the FDA rejected the ba.1 bivalent booster because the agency felt that the boosters may fail to provide adequate protection against the newest strains, ba.4 and ba.5, which At that time they were spreading rapidly in America and the rest of the world. , So the FDA asked Pfizer-BioNtech and Moderna to develop bivalent vaccines specifically targeting BA.4 and BA.5 instead of BA. Because clinical trials take time, the FDA was prepared to consider animal testing and other laboratory findings to decide whether to authorize a bivalent booster. This decision has sparked controversy as to whether it is appropriate for the FDA to approve boosters without the backing of direct human data. However, the FDA has said that millions of people have safely received mRNA vaccines — which were originally tested in humans — and that changes in mRNA sequences in vaccines do not affect the safety of the vaccine.

Thus, it is concluded that bivalent vaccines are safe and there is no need to wait for human clinical trials. Based on the evidence available from previous COVID-19 vaccines, we believe it is very likely that the new boosters will continue to provide strong protection against hospitalization and death from severe COVID-19. But whether they will protect against re-infection and new infection remains to be seen.

  1. Will it be a booster shot only? Bivalent vaccines can only be used as a booster shot for at least two months after the completion of the primary series — or the initially required shots — or after a previous booster shot. Modern bivalent vaccine is authorized for people 18 years of age, while Pfizer bivalent vaccine is authorized for people 12 years of age and older.
  2. Will the new shots protect against future variants? How well bivalent vaccines will perform in the face of new variants will depend on the nature of future spike protein mutations. If it is a minor mutation or set of mutations compared to the original strain or the Omicron variants BA.4 and BA.5, the new shots will provide good protection. However, if a hypothetical new strain has highly unique mutations in the spike protein, it is likely that it may once again evade immune defenses. On the other hand, the successful development of updated vaccines shows that mRNA vaccine technology is so rapid and innovative that it is now possible to develop and distribute new vaccines – within months of the emergence of a new variant.
Advertisement