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The drugmaker AstraZeneca announced on Monday that an early analysis of some of its late-stage clinical trials, conducted in the United Kingdom and Brazil, showed that its coronavirus vaccine was 70.4 percent effective in preventing Covid-19, suggesting that the world could eventually have at least three working vaccines — and more supply — to help curb the pandemic.
The British-Swedish company, which has been developing the vaccine with the University of Oxford, became the third major vaccine developer in this month to announce encouraging early results, following Pfizer and Moderna, which both said that their vaccines were about 95 percent effective in late-stage studies.
AstraZeneca’s results are a reassuring sign of the safety of the vaccine. It came under