Study finds one vaccine may make more antibodies, but does it matter?
Ten months ago, the results of large clinical trials appeared almost too good to be true: Two messenger RNA vaccines reduced symptomatic COVID-19 cases by more than 90% in almost every group that got them.
Now, subtle differences between the Pfizer Inc.-BioNTech SE and Moderna Inc. vaccines are emerging across patient groups over time. One small U.S. study found waning levels of antibodies with Pfizer’s vaccine, particularly in an older group of people. And a larger study from Belgium found that Moderna’s shot may generate more antibodies than Pfizer’s.
But what this all means in the real world is still unclear. Researchers are still working to understand the nuances of how long their protection lasts, and how it differs from one person to another.
Getting answers to those questions is a crucial step to determine who might need a booster shot. The more infectious delta variant, the rise of which has coincided with slight drop-offs in vaccine effectiveness, has raised the stakes and led governments to begin rolling out a third dose of the shots. The Food and Drug Administration will hear public arguments on Sept. 17 about whether to go ahead with booster shots of Pfizer’s vaccine.
Much of the focus has been on levels of antibodies, which serve as one of the immune system’s front-line defenses. One theory about Moderna’s vaccine is that it creates more of those antibodies because it uses a larger dose and the two doses are administered over a oneweek longer interval than Pfizer’s.
But antibodies are just one component of immunity, and it isn’t clear if they are the most important one, especially over the long-term.
Along with shorter-lasting antibodies, COVID-19 vaccines also trigger what’s essentially a long-term memory in the immune system. That memory appears to increase and become better at making variant-fighting antibodies over time. That longer-term protection, which includes what are known as T cells and memory B cells, is harder to measure in the lab than antibodies. But it’s thought to play an important role in preventing severe illness and hospitalizations.