The Effect of Oral Levamisole Co-administration on the Level of Immune Response to Hepatitis B Vaccine in Healthy Individuals: A Randomized Clinical Trial

Despite its proven efficacy, the hepatitis B vaccine requires improvements in immune enhancement and durability, especially in the elderly. Levamisole, an immune modulator, has been tested as an adjuvant to hepatitis B vaccine in several studies in immune-compromised populations. However, we aimed to evaluate the effect of levamisole on the immune response to hepatitis B vaccine in healthy subjects. In this randomized clinical trial, healthy family members of chronic hepatitis B patients were given twenty-microgram intramuscular injections of hepatitis B vaccine at 0, 1, and 6 months and 50 miligrams of oral levamisole twice a day for two weeks with every vaccination dose. Serum hepatitis B surface antibody (HBsAb) levels of ultimately 98 individuals were measured one month after the final vaccination dose and compared to those of 119 subjects that received placebo and vaccine with an identical regimen. HBsAb levels 10 mIU/mL were considered protective. The Student’s t-test, Mann-Whitney test, Kruskal–Wallis analysis (quantitative comparison in age groups), Chi-square test, and the Pearson correlation were used to analyze data. p 0.05 was considered significant. Serum HBsAb levels were significantly higher in the test group (p 0.001). All test subjects had levels above 50 mIU/mL (86.7% exceeding 100 mIU/mL). The quantitative response according to age groups was remarkable (p=0.01 and p 0.001 for placebo and levamisole, respectively), while that of gender was insignificant (p=0.9). Unlike HBsAb titers amongst controls, levels in the levamisole group were affected by smoking (p=0.79 and p=0.006, respectively). We conclude that oral levamisole as an adjuvant to the hepatitis B vaccine enhances the anti-HBs antibody in healthy vaccinees.