Figure 4.

Neutralization activity is defined by the occurrence of symptoms. (A) Violin plots show the distribution of neutralization titers of sera derived from derived from asymptomatic individuals (red) and symptomatic patients (blue) during April and October 2020. Boxes depict medians (middle line), 75% quartiles (upper bound), and 25% quartiles (lower bound). Whiskers indicate 1.5-times interquartile ranges above and below boxes. The table below the figure highlights the number of clinical specimens that have been assessed. Statistical analysis was performed by two-tailed Mann-Whitney U test. Asterisks depict levels of significance as follows: **p < 0.01; ****p < 0.0001. (B) Like in (A) but the frequencies of individuals exhibiting indicated neutralizations titers are depicted. (C) Sequential sampling and analyses of neutralization activity in 17 asymptomatic individuals and 54 symptomatic COVID-19 patients. Different colours highlight different trends as follows: purple: declining trend; black: increasing trend; light blue: unchanged neutralization.