One Vaccine Makes More Antibodies Than Another. Does It Matter?

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.

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. While billions of doses of vaccine have been administered around the world, 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, especially for older people and those with weakened immune systems. 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 or not to go ahead with booster shots of Pfizer's vaccine.