Pfizer's COVID-19 vaccine has 30 micrograms of mRNA, while Moderna's has 100 micrograms. Scientists have speculated that this could be a reason Pfizer's shot produced a lower antibody response than Moderna's in recent studies.
Pfizer /BioNTech "used the minimum dose level" to get an immune response that was stronger than catching COVID-19. A higher dose might have risked more side effects
A study of 1,600 Belgian health workers found that Moderna's COVID-19 vaccine produced twice as many antibodies as Pfizer's at six to 10 weeks after vaccination.
The authors said that the higher mRNA levels in Moderna's vaccine and a longer interval between doses "might explain this difference."
A study from the University of Virginia found no difference in antibody response among age groups with Moderna's vaccine but a lower antibody response in people 50 and older with Pfizer's. The researchers said that the differences could relate to the amount of mRNA in the vaccines