The Qatar study people, apparently:
The vaccine's weakening protection may be due to people's behavior, the study authors noted.
"Vaccinated persons presumably have a higher rate of social contact than unvaccinated persons and may also have lower adherence to safety measures," they wrote. "This behavior could reduce real-world effectiveness of the vaccine as compared with its biologic effectiveness, possibly explaining the waning of protection."
The studies were published Wednesday in the New England Journal of Medicine.