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Al-Marsad Journal: A study prepared by U.S. health officials has shown that the efficacy of the Pfizer and Moderna coronavirus vaccines has increased from 91% to 66% since the delta mutant became widespread in the United States.
Weekly checks
The study, which was tested on thousands of employees at health centers and hospitals in six states, was prepared to study the effectiveness of the two vaccines, according to tests done weekly on volunteers to monitor infections with and without symptoms.
The vast majority of health workers have received one of these two vaccines.
decrease in efficiency
Between December 2020 and April 2021, the effectiveness of these two vaccines in preventing infection with the virus was 91%, according to data released by the Centers for Disease Control and Prevention, the country’s main federal agency.
But in the weeks when the delta mutant became dominant, accounting for more than 50 percent of infections, the effectiveness fell to 66 percent.
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