St. John's Well Child & Family Center workers prepare to test a woman for COVID-19 at a free mobile test clinic set up outside Walker Temple AME Church in South Los Angeles amid the coronavirus pandemic on July 15, 2020 in Los Angeles, California./Credit: Mario Tama/Getty Images
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Previous vaccines and masks may hold down Covid-19, some researchers say
As US leaders work to control the spread of coronavirus, researchers across the globe are working to answer the mysteries that remain around infections.
