/Further investigation of the relationship between serological profile and sex was performed using point-biserial correlation specifically developed for analysis of correlations between binary and continuous variables. Figure 5 shows antibody responses correlate with subjects' sex. Once again, SIgM and RIgM are positively correlated with sex in individuals over 60 years old following both dose 1 and dose 2 vaccination. As is typical of antibody response evolution through Ig isotype switching with repeated vaccination (or even repeated infection), IgM levels show a negative correlation with sex in the younger age groups with values higher in males than in females.