A new study conducted by the Centers for Disease Control and Prevention found that Moderna's COVID-19 vaccine is the most effective of the three vaccines authorized by the Food and Drug Administration at preventing hospitalization from the virus.
"Among U.S. adults without immunocompromising conditions, vaccine effectiveness against COVID-19 hospitalization during March 11- August 15, 2021, was higher for the Moderna vaccine (93%) than the Pfizer-BioNTech vaccine (88%) and the Janssen vaccine (71%)" the team wrote in the CDC's weekly report on death and disease," the CDC said in the report.
The researchers found that the effectiveness of Pfizer's vaccine started to diminish after four months compared to Moderna's vaccine, which dropped to 92%.
"Vaccine effectiveness for the Pfizer-BioNTech vaccine was 91% at 14 -120 days after receipt of the second vaccine dose but declined significantly to 77% at more than 120 days," the researchers said.
They did not determine why there was a drop-off after 120 days and cited several possible reasons.
"Differences in vaccine effectiveness between the Moderna and Pfizer-BioNTech vaccine might be due to higher mRNA content in the Moderna vaccine, differences in timing between doses (3 weeks for Pfizer-BioNTech versus 4 weeks for Moderna), or possible differences between groups that received each vaccine that were not accounted for in the analysis," they said.
Despite the drop-off and variation between the vaccines, the researchers said that all three offer "substantial" protection against being hospitalized with COVID-19.
"Although these real-world data suggest some variation in levels of protection by vaccine, all FDA-approved or authorized COVID-19 vaccines provide substantial protection against COVID-19 hospitalization," the report said.