A new study conducted by researchers from the University School of Medicine explored how COVID-19 vaccines impact consumers’ antibody response to the coronavirus. According to their findings, the vaccine was responsible for improving the quality of antibodies over the course of the first six months post-vaccination.
“If the virus didn’t change, most people who got two doses of this vaccine would be in a very good place,” said researcher Ali Ellebedy, Ph.D. “The antibody response we saw is exactly what we’d expect from a robust immune response. We never thought that six months following that second injection, many people would still be actively improving the quality of their antibodies. To me, that is remarkable.
"The problem is that this virus keeps evolving and producing new variants. So, the antibodies are getting better at recognizing the original strain, but unfortunately the target keeps changing.”
Tracking the antibody response
For the study, the researchers collected blood samples, lymph node samples, and bone marrow samples from different groups of participants; none of the participants had tested positive for COVID-19. Blood tests and lymph node samples were collected prior to the first dose of the COVID-19 vaccine, as well as at six checkpoints after getting the vaccine; bone marrow samples were collected at about four months and six months post-vaccination.
The researchers learned that the strength and quality of the antibodies improved over time. This was first evidenced after analyzing how the antibodies interacted with germinal centers in the body; germinal centers are where immune cells get stronger to provide protection against infection. Antibodies improve in quality the longer they stay in germinal centers.
This study showed that at the six-month mark, the majority of participants still had antibodies in their germinal centers, which is a key indicator of strong protection against COVID-19.
The researchers were surprised by this discovery after six months because there has been anecdotal evidence that consumers have a weaker immune response to COVID-19 over time. However, this might be due to there being fewer antibodies, not weaker ones.
“When you look at antibodies, quantity should not be your only concern,” Ellebedy said. “The antibodies at six months might be less in quantity, but they are much better in quality. And that refinement of the antibody response happens on its own. You get your shot, maybe your arm hurts for a day, and then you forget about it. But six months later your germinal centers are still ongoing and your antibodies are still getting better and better.”
After analyzing the blood samples, the researchers found similar results. Over time, the antibodies got stronger and were more likely to protect participants from infection. In the early weeks after vaccination, the antibodies were 20% likely to be bound to a COVID-19 protein; by six months after vaccination, that figure jumped to 80%.
While these findings are positive in terms of long-term virus protection, the researchers explained that mutations to the COVID-19 virus may put these findings into question.
“Everything changes when a new variant comes,” Ellebedy said. “You have to retrain your immune system. It’s like updating your anti-malware software to make sure it matches the newest computer viruses that are going around. It doesn’t mean the old software was bad. It just means it no longer completely matches the viruses it is going to encounter.”