還有這兒

也是CDC網站上的。注意圖中的紅線（代表無症狀感染者）的水平幾乎不隨時間流逝而減低。

https://wwwnc.cdc.gov/eid/article/27/1/20-3515_article

 

 

 

 

In this study, the initial neutralizing antibody reaction appeared to correlate with the severity of the disease. However, patients with pneumonia were considerably older than asymptomatic persons, and increasing age is associated with a stronger neutralizing antibody response (10). In this study, neutralizing antibody titer decreased more in symptomatic than asymptomatic patients.