Both infection and vaccination can lead to immunity when it comes to SARS-CoV-2, the virus behind COVID-19. Two of the vaccines that provide immunity to SARS-CoV-2 are Pfizer’s and Moderna’s mRNA offerings, both of which provide considerable protection from the virus a month or two after administration of the second dose. A new preliminary study evaluated the mechanisms by which the vaccines offer protection against the virus and compared the data to that of people who developed immunity through infection.
The study involved comparing the immune response in individuals who were given two doses of an mRNA vaccine to unvaccinated individuals who had contracted the virus and were recovering from asymptomatic COVID-19. The researchers aimed to explore the mechanisms behind the immune response that results from mRNA vaccines compared to infection with the virus.
Similarities in immune response between the individuals who were vaccinated and those who had contracted the virus were similar, though, at the cellular level, the researchers noted some differences between the two. Both pathways to immunity resulted in the development of neutralizing antibodies.
The researchers explained:
In this study, we aimed to address two questions: What are the functional and transcriptomic responses of memory T and B cells to mRNA-based COVID-19 vaccination? And how does the vaccine response differ from that of an asymptomatic SARS-CoV-2 infection?
Though the researchers were able to detect antibodies in participants after two weeks from the first dose (in some cases), they report that the level spiked substantially after the second mRNA vaccine shot. After the first vaccine dose, the concentration of neutralizing antibodies was similar to that of individuals who had contracted the virus.
However, the second ‘booster’ dose of the vaccine resulted in significantly higher amounts of antibodies compared to the convalescent participants, though the study notes that important B cell adaptations were found in both groups of people. A key aspect of the findings is that around two weeks after the second mRNA shot, the researchers noted an ‘adaptive immune response’ that contributed to ‘future recall responses’ toward the virus in fully vaccinated individuals. The study goes on to state:
Both mRNA vaccines induce potent and durable neutralizing antibodies as early as 10 days (5) and last as long as seven months after the first dose of vaccination (12). Our data suggest that while neutralizing titers after the first dose are comparable to those observed in recovered individuals, levels of neutralizing titers are significantly higher than both groups following the second vaccination dose.
Ultimately, the study found evidence that the mRNA COVID-19 vaccines from Pfizer and Moderna are able to trigger an adaptive immune response to SARS-CoV-2 that includes a recall response in the case of future infection with the virus. The recall response is a key element of reducing the severity of infection from the virus and preventing the development of COVID-19 as a result. It’s important to note that the study is preliminary at this time and hasn’t yet been peer-reviewed.