Countries such as the UK and the US have been launching bivalent boosters since September last year. These vaccines are expected to protect against coronavirus infection better than the original vaccine.
Everything seemed happy here until some research came out suggesting that immune imprinting might make bivalent boosters less effective than people expected.
In early January, the New England Journal of Medicine (NEJM) published two articles stating that the bivalent booster was believed to be able to defeat the Covid-19 strain and that the Omicron strain did not produce the same amount of antibody response. larger than the original mRNA. Vaccine.
Immune imprinting is considered to be the main reason behind this.
What are immune markers?
Immune signature is nothing more than the tendency of the body to recur an immune response based on the first variant it was exposed to, whether by infection or vaccination, in case it encounters a new or slightly different variant. slightly different of the same pathogen.
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Findings so far!
It was in 1947 when the concept of immune markers first came to light. Scientists observed that the bodies of people who were previously infected with flu and vaccinated against the current flu strain produced antibodies against the first strain they were exposed to. This was found in a report released in the magazine Nature.
At that time, it was called “original antigenic sin”. However, today this concept is called imprinting.
In the coming years, scientists came to the conclusion that this imprinting serves as a database for the body’s immune system. This database helps the body respond better to repeated infections.
When the body is exposed to a virus for the first time, it forms memory B cells. These cells circulate in the blood. They then quickly produce antibodies as soon as the body is exposed to the same virus strain again.
Isn’t that a good mechanism of the body?
It’s a beneficial mechanism, but not always. The problem arises when a variant of the virus that is similar but not actually the same virus comes into contact with the body. In these cases, the body’s immune system activates memory B cells instead of creating new B cells. Now, when these memory B cells are created, they produce antibodies that bind to the characteristics observed in both strains, the old strain and the new strain. This is called cross-reacting antibodies.
Now, cross-reactive antibodies are not completely wasted; they provide protection against new strains. However, they are not as effective in protecting the body compared to those produced by B cells in case the body encounters the original virus for the first time.
What do recent studies say?
Researchers from the Vagelos College of Physicians and Surgeons of Columbia University in New York conducted a study in which 40 people participated. These people were vaccinated with three doses of the monovalent vaccine (original vaccine). In the trial, 19 of these 40 participants received a booster (actually a fourth shot) of the monovalent (original) vaccine. The remaining 21 participants received a booster shot of the new bivalent vaccine.
The experiment showed that the bivalent booster vaccine did not induce a peak virus-neutralizing antibody response that was significantly greater than the original monovalent vaccine.
In another study, researchers from Beth Israel Deaconess Medical Center in Boston observed immune responses in 15 individuals. These participants received an initial monovalent enhancer, whereas in 18 other participants, a bivalent enhancer response was recorded.
As a result, it was found that median BA.5 (Omicron) neutralizing antibody titers were similar to mRNA enhancement after mono- and bi-chemotherapy, with a modest trend in favor of the enhancer bivalent with coefficient 1.3.
These two studies and many others point to the fact that immune imprinting can create a barrier to the effectiveness of bivalent vaccines.
In 2022, Professor Rosemary Boyton and her team conducted a study at Imperial College London on the same issue. The professor and team found that Omicron infection had negligible or no beneficial effect in strengthening any part of the immune system. The study included more than 700 participants. The immune systems of these 700 participants were imprinted with older coronavirus variants.
David Ho, the author of the Columbia University study stated in an interview that they were somewhere expecting the results they found. In vaccinology, there is a phenomenon called immune imprinting, which means “immune memory preferentially sees what has been seen before”.
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If bivalent enhancers are not as effective as monovalent enhancers, can you omit them?
Are not. David Ho clarified the doubt by saying that even if the boosters are not as good as the original ones, people should still buy bivalent boosters.
What does the World Health Organization (WHO) say?
The World Health Organization (WHO) warned last year, saying: “The majority of the benefit comes from booster vaccine delivery, regardless of whether it is monovalent or bivalent.”
Regardless of the type, vaccines against the coronavirus are extremely important in preventing severe disease, scientists suggest. However, there is now an urgent need to introduce a vaccine that is able to counteract the immune signature, while also combating the transmission of the virus.
Is there a way to deal with immune markers?
Currently, there are many studies looking for a method to disrupt immune signatures. Some scientists think intranasal vaccines may prevent infection better than injectable vaccines.
These scientists suggested that mucous membranes would provide stronger protection, regardless of whether they carried traces of previous exposures or not.
Many researchers around the world are also aiming to find out whether a coronavirus vaccine could be produced annually and whether this could help avoid the problem of immune signatures. Are not.
David Ho also expressed in an interview that there are a lot of efforts towards developing a pan-sarbecovirus vaccine. These vaccines will protect against all variants that cause COVID. These vaccines can even protect us from SARS and other viruses. However, one should not expect the development of such a vaccine overnight. Efforts will take time to yield results.
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Source: pagasa.edu.vn