According to a research done in Belgium Moderna's COVID-19 vaccine makes more than twice as many antibodies as Pfizer's.
The results were published on the Journal of American Medical Association website on Monday.
The study involved a group of 1,600 people whose blood samples were analyzed 6 to 10 weeks after their second doses.
Antibodies are known to be a key component of a human body's immune response, but the study didn't examine whether more antibodies meant a longer period of immunity before waning.
Both Moderna and Pfizer's mRNA vaccines have reported more than 90 percent effectiveness during the third phase of the clinical trials.