Approximately 221 million doses of the Pfizer-BioNTech vaccine have been administered in the United States compared to approximately 150 million doses of Moderna's vaccine. In several studies published in recent weeks, most still pending peer review, Moderna's vaccine appeared to be more effective in the long term than the Pfizer-BioNTech vaccine.
Research published by the Centers for Disease Control and Prevention (CDC) found that the effectiveness of the Pfizer-BioNTech vaccine fell from 91% to 77% after a four-month period after the second injection. During the same time period, the Moderna vaccine showed no decrease in its protection against hospitalization.
The New York Times reports that if the efficacy gap continues to widen, it may have implications for the booster vaccine debate. Currently, public health institutions around the world are considering recommending a third injection of the Pfizer-BioNTech vaccine for some high-risk groups. This journal also notes that the data indicating that effects vary is based primarily on observations, as vaccines have never been directly compared in a carefully designed study, and therefore need to be viewed with some caution.
