With so many areas in the United States with low vaccination rates, the spread of the Delta variant of the coronavirus will make it that much harder for the country to reach herd immunity, a top expert says.
원문출처 : https://www.cnn.com/2021/07/03/health/us-coronavirus-saturday/index.html
원문출처 : https://www.cnn.com/2021/07/03/health/us-coronavirus-saturday/index.html