Zoom in: In a study released last week, the CDC found that Moderna was significantly more effective against hospitalizations and emergency department or urgent care encounters than the Pfizer or J&J vaccines.

A second smaller study found more similar effectiveness level against hospitalization between the two mRNA vaccines…

Possible reasons for the difference include that Moderna has a much higher dosing regimen than Pfizer, and the second shot is given after a slightly longer interval.

And, while the vaccines are both made using mRNA technology, they have structural differences.