A small new study suggests that Pfizer-Biotech’s COVID-19 vaccine may provide protection against neocoronaviruses for several years if they do not evolve significantly.
The degree of vaccine protection depends on how much and how fast the virus evolves, and how powerful different types of vaccines are at eliciting a durable immune response. The Pfizer vaccine uses mRNA to train the immune system to fight SARS-CoV-2. Although the mRNA vaccine greatly exceeded experts’ expectations and showed high efficacy in protecting against SARS-CoV-2, it is not clear how long this protection will last.
To find out, a group of researchers recruited 41 participants who received two doses of the Pfizer vaccine, and eight people who had previously been infected with SARS-CoV-2. The researchers collected blood samples at the beginning of the study, and then collected blood samples 3, 4, 5, 7, and 15 weeks after the participants received the first dose of the vaccine.
Consistent with previous studies, the researchers found that the mRNA vaccine induced a strong antibody response, and those who were newly crowned recovered (mildly ill) responded even more strongly after vaccination.
The team also collected lymph node samples from 14 people over the same time span, none of whom had been previously infected with SARS-CoV-2. In response to the infection and the vaccine, short-lived molecular structures known as germinal centers formed in the lymph nodes. Lymph nodes are glands that hold cells of the immune system and usually swell in response to infection.
In people infected with SARS-CoV-2, these structures form in lymph nodes in the lungs, which are difficult to obtain, whereas vaccines usually stimulate the production of these structures in the armpits, which are more readily available.
Such structures train a type of immune cell called a B cell to better bind to SARS-CoV-2 over a period of weeks or months. This process produces highly trained immune cells, some of which are memory cells that remember the virus over time.
In the new study, the researchers found that in most of the vaccinated participants, their germinal centers continued to be active, training these strong immune cells for at least 15 weeks after the first injection.
According to the researchers, “Because this germinal center response continues for months, it may produce many memory cells that can last for years, some of which may take root in the bone marrow and produce lifelong antibodies.”
While the authors did not observe people who received the Moderna vaccine, they believe that the response may have been similar, as this is also an mRNA vaccine that shows comparable efficacy.
But that doesn’t necessarily mean people don’t need booster shots.
The need for booster vaccinations will depend on how far the virus has evolved and whether the cells produced by the biogenesis center are strong enough to handle the significantly different mutations. In addition, not everyone is able to produce an equally strong immune response; some people, such as those with suppressed immune systems, may need booster shots.
The findings are published in the June 28 issue of the journal Nature.
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