While the race for a Covid-19 vaccine continues, scientists are learning more about the early vaccines used to fight smallpox, the only human infectious disease to be successfully eradicated.
원문출처 : https://www.cnn.com/2020/07/21/us/smallpox-vaccination-virus-eradication-scn-trnd/index.html
원문출처 : https://www.cnn.com/2020/07/21/us/smallpox-vaccination-virus-eradication-scn-trnd/index.html