Fig. 6

Recognition of recombinant RBD and RBD-P by human IgG polyclonal antibodies. The ELISA was performed using sera samples from no hospitalized individuals convalescing from COVID-19 (median age around 40 years). Also, twelve human sera obtained before the COVID-19 pandemic were used as control. Infection with SARS-CoV-2 was confirmed by RT-PCR from nasopharyngeal swabs performed in clinics. In boxplots, each data point is the mean and its deviation of replica per serum. Also, each boxplot presents the mean in a dotted line, the median as the middle line, the interquartile range as box limits, and the 2.5th and 97.5th percentiles as the whiskers. For all variables with the same letter, the difference between the means is not statistically significant. If two variables have different letters, they are significantly different (p < 0.05)