Effect of Zinc Supplementation on Serological Response to Vaccination Against Streptococcus Pneumoniae in Patients Undergoing Chemotherapy for Colorectal Cancer

The aim of the study was to evaluate the effect of zinc supplementation on the antibody titer and the 23-valent pneumococcal seroconversion after vaccination in patients undergoing chemotherapy for colorectal cancer. The study included 25 patients undergoing postsurgery chemotherapy for colorectal adenocarcinoma (chemo group). Subjects were assessed in the perioperative period (prevaccination), before chemotherapy (4thwk) and after 3 cycles of chemotherapy (16thwk). Thirty-two healthy volunteers (control group) were included in the study. Participants received the 23-valent pneumococcal conjugate vaccine, and capsules containing zinc (Zn) sulfate (70mg daily) or identical placebo capsules (containing wheat starch with no added Zn) for 16wk and were randomly allocated on one of the following groups: chemo-Zn (n = 10), chemo-placebo (n = 15), control-Zn (n = 21), and control-placebo (n = 11). The antipneumococcal antibody titer against 6 polysaccharides was analyzed by ELISA and compared using linear mixed models. The seroconversion rate was compared using Fisher's exact test. An immune response to the vaccination against pneumococcus was observed in all participants. In the 16thwk, the polysaccharide 6 concentration was lower in the chemo-Zn group [2.96 (1.74-5.03) g/mL] compared with the Chemo-Placebo group [10.75 (5.37-21.54) g/mL] and the seroconversion rate was lower in the chemo-placebo (36%) compared with the control-placebo (85%) (P = 0.027). Zinc supplementation did not change the antibody titer after vaccination. However, the lower seroconversion rate observed in the chemo-placebo suggests an influence of zinc in the vaccinal protection.