According to a large study by US health workers published on Tuesday, the effectiveness of the Pfizer and Moderna Covid 19 vaccines against infection fell from 91% to 66% after the Delta variant.
Both Centers for Disease Control and Prevention (CDC) are reviewing the real-world performance of vaccines as they were authorized among first-time healthcare personnel, first responders and other front-line workers.
Thousands of workers in six states were tested weekly and at the onset of Covid 19 symptoms, allowing researchers to gauge their effectiveness against symptomatic and non-symptomatic infections.
The effectiveness of the vaccine was estimated at 91% during the initial study period from December 14, 2020 to April 10, 2021, considering the rate of infection and the time it took for people to be infected with the vaccine and immunizations.
But in the weeks leading up to August 14, when the highly contagious Delta type prevailed, the effectiveness dropped to 66%.
The report’s authors said there were several warnings, including that vaccine protection could be reduced over time, and that 66% of the estimates were based on a relatively short study period with some infections.
“Although these interim results suggest a moderate reduction in the effectiveness of the COVID-19 vaccine in preventing infection, a two-thirds reduction in the risk of infection indicates the continued importance and benefits of the COVID-19 vaccine,” he said. ۔ “
Numerous studies have now concluded that the efficacy of the vaccine has fallen against Delta, although the exact level of this drop varies between papers.
According to a recent CDC study of patients in New York, protection against acute illness appears to be more than 90% stable.
Another CDC study of Los Angeles patients, released Tuesday from May 1 to July 25, found that non-vaccinated people were hospitalized with Covid 19 rather than the vaccine. It is 29.2 times more likely to occur, which is about 97% efficiency.
In early July, the Delta became a major source of tension in the United States.
According to a recent article in the journal Virological, the amount of virus found in the first tests of Delta variant patients was 1000 times higher than in patients with the first wave of the virus in 2020, leading to a significant increase in her infectious disease. ۔
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