Evidence indicates that immunity following infection with SARS-CoV-2, the virus that causes COVID-19, lasts as long as 11 months. Questions remain, however, regarding the duration of immunity elicited by mRNA vaccines against the virus. Findings from a recent study indicate that mRNA vaccines elicit long-term immunity due to the presence of germinal centers in the lymph tissue.
Germinal centers are small, transient structures that form in the lymph nodes, gut, and spleen in response to an acute infection or vaccination. They produce plasma cells and memory B cells – long-lasting immune cells that secrete antibodies that provide protection against future reinfection. Germinal centers are important components of the body’s adaptive immune response.
The authors of the study conducted a two-part experiment. The first experiment involved 14 healthy adults who had received the Pfizer BioNTech COVID-19 vaccine and had never been infected with SARS-CoV-2. The authors of the study sampled cells taken from the lymph nodes of the participants three, four, five, and seven weeks after they received the first dose of the two-dose vaccine. They sampled lymph tissue from 10 of the participants 15 weeks after their first dose.
Analysis of the lymph tissue indicated that germinal centers were generating antibody-producing B cells three weeks after the initial dose. Germinal center activity remained high through successive weeks, and at 15 weeks after the first dose 80 percent of participants still demonstrated germinal center activity.
The second experiment involved 41 healthy adults who received the Pfizer BioNTech vaccine, including eight who had previously been infected with SARS-CoV-2. The authors collected blood samples from each of the participants before the first dose and again at four, five, seven, and 15 weeks afterward.
The blood samples revealed that antibody levels increased slowly among participants who had never been exposed to the virus, peaking about one week after the second dose. In contrast, antibody levels among those who had previously been infected with SARS-CoV-2 were high before the first dose. These levels increased rapidly upon vaccination and peaked higher than those who had never been infected.
These findings suggest that the immune response to mRNA vaccines is robust and long-lasting. They also underscore the value of vaccination even after having been infected with SARS-CoV-2.
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