Effect of oral levamisole on immunological response to hepatitis B vaccine in haemodialysis patients

SIRS, We read with interest the work of Fabrizi et al. addressing the role of levamisole on enhancing immunological response of the haemodialysis patients to hepatitis B virus (HB) vaccine. Fabrizi et al.’s intention-to-treat (ITT) analysis compared haemodialysis patients who received HB-vaccine plus levamisole with those who received HB-vaccine alone. Intention-to-treat analysis is an analysis based on the initial treatment intent, not on the treatment that was eventually administered. ITT analysis is intended to avoid misleading artefacts that can arise due to dropouts. If people in the intervention group tend to drop out at a higher rate because of safety reasons, even an ineffective treatment may appear to be beneficial in per protocol analysis. However, if dropouts are not because of adverse events, an ITT analysis can be misleading and undermine the clinical efficacy of the intervention. In Fabrizi et al.’s review, 44 patients (13.5% of the total studied population), who were in the ITT population but did not complete the vaccine schedule, are included – however, none of them failed to comply due to safety reasons. Including these patients seems to undermine the true efficacy of oral levamisole. The pooled result of ITT analysis by Fabizi et al. reports the effect of levamisole to be significantly lower than that of Alavian et al.’s per protocol analysis and the latter’s subgroup analysis including those who completed the vaccine schedule (OR 2.08 vs. 2.77 and 2.43, respectively). It is important to emphasize that, according to Alavian et al.’s meta-analysis, the role of levamisole in maintaining long-term HBsAb is greater than its contribution to post-vaccination anti-HBV immunity (3.96 vs. 2.77).