Correlation between infection intensity (log10 (x+1) transformed) and antibody levels (square root transformed). r is the correlation coefficient and p values are also given. The youngest age group (7–10) is excluded from the analysis as they are producing very little amounts ofanti-Sh13IgG3. a) Age group where infection levels peak (11–12 yearsold). b) Age group where infection levels are declining (13–16 years old). c) Age group where infection levels are lowest (17–18 years old).