Moderna’s COVID-19 vaccine more than doubled the level of antibodies compared to the Pfizer vaccine, according to a study of healthcare workers in Belgium, researchers found.
A research letter published in JAMA drew from 2,499 healthcare workers who received two doses of either the Pfizer/BioNTech vaccine or Moderna’s shot. Researchers looked at antibody levels in blood tests before vaccination, and up to 10 weeks following participants’ second dose.
Overall, the Moderna vaccine elicited an antibody level of 3,836 U/mL, compared to 1,444 U/mL following the Pfizer vaccine, and among participants previously uninfected, researchers reported 2,881 U/mL for Moderna versus 1,108 U/mL for Pfizer. Study authors suggested the difference could be explained by the higher mRNA content in the Moderna vaccine, and the longer gap between the first and second dose (4 weeks vs 3 weeks for Pfizer).
“A relationship between neutralization level after SARS-CoV-2 vaccination and protection against COVID-19 has been demonstrated by several studies,” the letter reads. “As such, the height of the humoral response after vaccination, which correlates with neutralizing antibody titers, might be clinically relevant.”
The study had its limitations, like lacking data on cellular immunity, and the focus on healthcare workers. Researchers said further research is needed to determine whether the differences in antibody level conveys a difference in lasting protection.
Separate findings from the Mayo Clinic recently indicated the Moderna vaccine cut COVID-related hospitalizations by about half the rate compared to the Pfizer vaccine. Study authors suggested several factors behind the differences observed among the Pfizer and Moderna vaccines, including the dosing, meaning “each mRNA-1273 [Moderna] dose provides three times more mRNA copies of the Spike protein than BNT162b2 [Pfizer], which could result in more effective priming of the immune response.”