https://blog.wongcw.com/2021/02/12/%e7%be%8ecdc%e7%a0%94%e7%a9%b6%e9%a1%af%e7%a4%ba%e6%88%b4%e5%85%a9%e5%80%8b%e5%8f%a3%e7%bd%a9%e5%b0%8dcovid-19%e4%bf%9d%e8%ad%b7%e5%8a%9b%e6%9c%89%e9%a9%9a%e4%ba%ba%e5%bd%b1%e9%9f%bf/
美CDC研究顯示戴兩個口罩對COVID-19保護力有驚人影響