The new coronavirus continues to mutate, and the mutant strains give birth to subtypes. The subtype of Omicron starts from BA.1, and now BA.4 / BA.5 has become the dominant strain in many areas. The existing vaccines mutate to Omicron The effectiveness of the “offspring” of the strain has also attracted more attention.
Two separate studies published in June 2022 shed some light on the answer to this question.
A report published by a Chinese research team in the journal “Nature” and a report by a British research team in the journal “Science” examined the causes of repeated infection with the new crown from different aspects.
“Broad Spectrum Immunity”
A research paper published by a Chinese research team in the journal Nature on June 17 stated that the vaccine currently developed for the early variant of Omicron has been escaped by the newly emerging subtype, so it may not be able to target the emerging subtype. Omicron subtype variants confer immune protection.
This research was led by the team of Professor Xie Xiaoliang from Changping Laboratory of Beijing Future Genetic Diagnosis Advanced Innovation Center of Peking University, and participated by Tsinghua University, Nankai University, Academy of Social Sciences, Capital Medical College and other institutions.
The study found that after the vaccinated people were infected by the early Omicron strain BA.1, they produced antibodies that could neutralize the BA.1 virus and the original new coronavirus, and the subtypes that appeared later, including BA. 2.12.1, BA.4 and BA.5, all have mutations that escape these antibodies.
These subtype variants were found to have greater escape capacity for neutralizing antibodies in plasma from patients who received three doses of the vaccine and were infected with Omicron BA.1 post-vaccination.
Neutralizing antibodies inactivate the virus and help provide “broad-spectrum immune” protection.
The team explained that the omicron subtype variant can break through the humoral immunity (antibody immunity) protection caused by the omicron virus itself, and the memory immunity generated by this breakthrough infection is mainly directed against the original strain.
Vaccines made with early mutants of Omicron have limited neutralization of emerging subtypes.
In this regard, the research team of Peking University believes that such vaccines may not be able to play a “broad-spectrum” immune protection effect against the new Omicron subtype variant.
“Unlike when Omicron first appeared, today’s Omicron subtype variants can target the humoral immunity (breakthrough infection) induced by Omicron itself, such as in Omicron after vaccination,” the study wrote. Micron infection.”
Omicron’s breakthrough infection-induced memory immunity was primarily against the original SARS-CoV-2 strain, and “this in turn narrows the diversity of antibodies elicited and may further facilitate the emergence of future variants.”
The Imperial College London research team published a paper in the journal Science on June 14, saying that Omicron infection does not necessarily enhance natural immunity to emerging virus variants and subtypes. The immune-enhancing effect of infection is more dependent on the individual’s infection history.
Studies have shown that an individual’s vaccination and infection history can have a huge impact on their immune response to variants, including to Omicron.
This is because of the role of “immuno-imprinting”; the memory and immunity of the “imprinting” left at the time of the initial infection to the virus that invaded at that time has nothing to do with Omicron and its subtype strains.
This goes against a common assumption. Infection with the virus is often thought to provide a natural boost of immunity, allowing a person to better recognize the variants encountered and defend against future infections, but new analysis finds that even people who have received three doses of the vaccine are still re-infected, including Reinfection with the Omicron variant and its various subtypes.
The research team found that among those who had received three doses of the vaccine and had not previously been infected with the new crown, after infection with Omicron, the body was immune to multiple previous variants (Alpha, Beta, Gamma, Delta and the original virus strain) Enhanced, but less immune-enhancing effect on Omicron itself.
People who recovered from the initial infection in the outbreak were later infected with the Omicron variant, and the first infection did not act as an immune booster.
This is because the study found that T cells cannot make up for the poor recognition ability of Omicron antibodies. Even in patients infected with this mutant strain, T cells still have poor recognition of the spike antigens of the mutant strains, which cannot be used to identify the mutants. provide effective protection.
Therefore, the report’s lead author, Rosemary Boyton, a professor in the Department of Infectious Diseases at Imperial, explained that having been infected with Omicron once did not equate to greater immunity to it and would not be re-infected. .
“The concern is that Omicron may mutate further into a more pathogenic strain, or become better able to overcome vaccine protection,” she said. In this case, people infected with Omicron It will be difficult to fight off future infections, depending on their immunoblotting.”
One of the report’s authors, Dr Joseph Gibbons from Queen Mary University of London, explained: “The link between a person’s infection history and their response to vaccines is now clear. Previous infection with different variants affects the The potency and durability of the immune response.”
However, they stress that it is certain that vaccination can provide continued protection against severe illness and death, but the impact of infection and reinfection on long-term health, including “coronavirus,” is unclear.
How does immunity arise?
The immune system is the body’s defense system against infection and consists of two parts: the innate immune response and the adaptive immune response. The innate immune response does not learn and does not target any specific virus, and therefore does not develop immunity to the new coronavirus.
The adaptive immune response is more targeted, producing cells that target antibodies that can stick to the virus and block it, and T cells that recognize the virus and target infected cells, a cellular response.
Research shows that it takes about 10 days to develop antibodies against the new coronavirus, and that the sickest patients develop the strongest immune responses.
Preliminary studies have shown that there is no weakening of T cells and immune memory after vaccination with the new crown vaccine, but the latest research shows that the advantages and disadvantages of this feature for “broad-spectrum” immune protection need to be further explored.
Why are neutralizing antibodies more important?
The COVID-19 coronavirus has a protective coating of ribonucleic acid (RNA) with spike proteins that attach to certain human cells. Once the viral RNA enters the cell, it begins to replicate and initiate the production of proteins, causing the virus to infect more cells and spread throughout the body, especially the lungs.
The immune system responds to different parts of the virus, but the focus is on the spike protein, which recognizes it as foreign and automatically starts producing antibodies in response.
Neutralizing antibodies are antibodies produced by the body’s immune system that attack the coronavirus‘ spike protein, making it harder for the virus to attach and enter human cells, according to the Harvard Medical School website. Neutralizing antibodies can provide longer-lasting protection against reinfection than binding antibodies.
Man-made versions of neutralizing antibodies, called monoclonal antibodies, are approved for clinical treatment of COVID-19 in some countries, including the United States.