On June 28, the top academic journal Nature published an online paper in the form of "Accelerated Article Preview" to answer this key question. The paper pointed out that this is the first study to provide evidence for "(COVID-19 vaccine) vaccination can continuously induce cellular responses against specific antigens in the human body".
Researchers pointed out that in this epidemic, a new type of vaccine called "mRNA vaccine" turned out to be used in many countries and regions to fight the epidemic. Despite the excellent protection demonstrated in clinical trials, such vaccines have never been approved by the regulatory authorities before, so it is unclear how long their protection effects will last.
Since several mRNA vaccines were authorized for emergency in the prevention of coronavirus, many scientists wanted to know whether their effects were long-lasting, but most of these studies only monitored the level of antibodies in the blood, and no one has looked at the source of the immune response to see whether the human body really produces lasting immunity.
"The germinal centers are the key to a lasting immune response," said Professor Ali H. Ellebedy, one of the leaders of this study. "The germinal centers are the place where immune memory is formed. The longer it exists, the stronger our immunity will be. The stronger it will be, the longer it will last. This is because there is a very strict screening process in the germinal center, and only the strongest immune cells can survive."
In other words, the germinal center is like a barracks for the immune system. Only trained immune cells that stand out can carry the banner of immunity against the COVID-19.
mRNA vaccine induces long-lasting immunity (image source: References [1])
In order to understand whether mRNA vaccines can induce an excellent "germinal center response", researchers have begun to study individuals who have received mRNA vaccines since December last year. Three weeks after the first vaccination, all 14 volunteers participating in the study had germinal centers that produced antibodies against the novel coronavirus in their lymph nodes.
It is worth mentioning that the response of these germinal centers can last a long time. After the second injection, the response level of the germinal center remained high. 15 weeks after the first vaccination, 8 of the 10 people tested still have germinal centers for the novel coronavirus, indicating that the immune system is still continuously training B cell recruits to produce antibodies.
"These evidences indicate that there is a very strong immune response in the body," said Professor Rachel M. Presti, another person in charge of this study. "Our immune system uses germinal centers to perfect antibodies so that they can bind antigens well and last as long as possible. If the antibodies in the blood are the final product of the immune response, then the germinal center is where the immune response originated."
Professor Ellebedy pointed out that the ability to maintain the germinal center activity 15 weeks after vaccination indicates that the immunity has not declined, which is excellent.
In addition to assessing the activity of the germinal center, the researchers also analyzed the blood samples of 41 volunteers (8 of whom had been infected with the COVID-19). Consistent with the results of other studies, volunteers who have not been infected with the COVID-19 began to develop antibodies after the first dose of vaccine, and the antibody level reached a peak after the second dose of vaccine. For volunteers who have previously been infected with the COVID-19, the antibody level will rise rapidly after the first shot.
These results also show that even if you have been infected with the COVID-19 before, vaccination can provide additional protection.
Taken together, the study shows that although mRNA vaccines are a new type of vaccine, they can achieve good results in inducing immune responses and providing long-term protection. At the end of the paper, the researchers pointed out that the success of the vaccine depends on whether it can trigger a long-lasting, high-affinity antibody response, and the mRNA vaccine against the novel coronavirus is undoubtedly on the right path.
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References:
[1] Turner, J.S., O’Halloran, J.A., Kalaidina, E. et al. SARS-CoV-2 mRNA vaccines induce persistent human germinal centre responses. Nature (2021).
[2] COVID-19 vaccine generates immune structures critical for lasting immunity, Retrieved June 28, 2021
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