Fig. 6

Effect of HBsAg antibody concentration on protection against malaria episodes. Association between categorized anti-HBsAg IgG responses and time to the first clinical malaria episode (a), and between continuous anti-HBsAg IgG responses and the hazard of first (b) and recurrent (c) clinical malaria events within a 12-month follow-up period. a Kaplan–Meier curves of time to first clinical malaria for subjects with anti-HBsAg IgG concentration in the upper (grey), intermediate (blue) and lower (yellow) tertiles. Median survival time (and 95% confidence interval [CI]) of subjects in each tertile and sample size stratified by age group are shown, as well as the p-value of the log-rank test comparing survival time across tertile-based categories. b One unit increase in continuous anti-HBsAg IgG protects from clinical malaria in analysis unadjusted and adjusted for anti-NANP IgG concentration. c One unit increase in continuous anti-HBsAg IgG protects from clinical malaria until day 180 and is significantly protective of recurrent events of malaria (95% CI excludes 1) but 180 days after vaccination associations become not statistically significant. Comparable results are shown in d when repeating analysis of recurrent malaria events but adjusting for anti-NANP IgG concentration (p-value of Schonfeld residual tests for analysis of recurrent events unadjusted for anti-NANP was 0.01 and adjusted for anti-NANP was 0.02, thus, rejecting a constant hazard ratio). All models were adjusted by study site and age cohort