Serological Changes against Hepatitis B Surface Antigen in Children and Adolescents Receiving Chemotherapy for Acute Leukemia.

BACKGROUND: Vaccination for hepatitis B virus (HBV) after chemotherapy among pediatric patients with acute Leukemia is still a debated issue. We investigated HBV immunity before and after chemotherapy and assessed immune response to re-vaccination after chemotherapy. METHODS: We retrospectively analyzed data of children and adolescents aged <19 years requested for vaccination after chemotherapy for acute leukemia to evaluate hepatitis B surface antibody (HBsAb) status before and after chemotherapy and to identify factors related to HBsAb positivity after chemotherapy. RESULTS: Of 89 enrolled patients, 61 (68.5%) with acute leukemia were HBsAb positive before chemotherapy. Of these 61 patients, 48 (78.7%) seroconverted to HBsAb negative status after chemotherapy; there were 76 (85.4%) HBsAb negative patients after chemotherapy. HBsAb positive patients when compared to HBsAb negative patients after chemotherapy had a significantly higher HBsAb positive rate (100.0% vs. 63.2%, p=0.008) before chemotherapy. Following HBsAb testing after one dose of the HBV vaccination, 33 (43.4%) of the 76 HBsAb negative patients seroconverted to an HBsAb positive status. HBsAb positive patients after a single dose of HBV vaccination had a significantly higher HBsAb positive rate at the time of diagnosis compared to HBsAb negative patients (84.8% vs. 48.8%, p=0.001). CONCLUSIONS: Based on these results, HBV re-vaccination after chemotherapy is recommended for all children and adolescents with acute leukemia. In addition, further investigation is required to improve the immunogenicity of HBV re-vaccination.

Immunogenicity and protective efficacy of a newly developed tri-component diphtheria, tetanus, and acellular pertussis vaccine in a murine model.

BACKGROUND/PURPOSE: Although assessing the immunogenicity and protective efficacy of acellular pertussis (aP) vaccines via murine model studies faces limitations, preliminary assessments have been achieved by evaluating respiratory challenge and humoral and cellular immunity. METHODS: We performed a long-term intranasal respiratory challenge with reference and clinically isolated strains of Bordetella pertussis. Simultaneously, we assessed humoral and cellular immunity for evaluating the immunogenicity of a newly developed tri-component diphtheria-tetanus-aP (DTaP) vaccine. Moreover, comparative assessment was made by performing the same evaluations with a commercially available tri-component DTaP vaccine as the positive control. RESULTS: Both groups showed significantly increased levels of antibodies against pertussis toxin, filamentous hemagglutinin and pertactin, and the levels of interferon-γ and interleukin-10 were significantly increased after two doses of vaccination. Furthermore, since cross cell-mediated immune reactivity between the two vaccines was detected, the possibility of interchangeability was indirectly suggested. Although the positive control group showed significantly higher titers in antibody responses for filamentous hemagglutinin and pertactin compared to the experimental group, anti-pertussis toxin antibody titers of the two groups were not significantly different and the protective efficacy against the clinical and reference strains was maintained in both groups for 18 weeks. CONCLUSION: The results showed inferior immunogenicity of the new DTaP vaccine compared to a commercial vaccine despite comparable cellular immunity and protective efficacy. Some efforts are necessary for improving immunogenicity against filamentous hemagglutinin and pertactin before conducting human clinical trials.

Immunogenicity and safety of the new reduced-dose tetanus-diphtheria vaccine in healthy Korean adolescents: A comparative active control, double-blind, randomized, multicenter phase III study.

BACKGROUND/PURPOSE: A new reduced-dose tetanus-diphtheria (Td) vaccine was developed in Korea, and phase I and II clinical trials were successfully undertaken. We conducted this double-blind, randomized, multicenter phase III clinical trial to assess the immunogenicity and safety of the new Td vaccine. METHODS: Healthy adolescents 11-12 years of age were enrolled and randomized to receive the new Td vaccine (study group) or a commercially available Td vaccine (control group). Blood samples were collected prior to and 4 weeks after the vaccination. Between the study and control groups, seroprotection rate, booster response, and geometric mean titer of antibodies against diphtheria and tetanus toxoids were compared after the vaccination. All solicited and unsolicited adverse events and serious adverse events during the 6-week study period were monitored. RESULTS: A total of 164 adolescents received vaccination, and 156 of them were evaluated to assess immunogenicity. The seroprotection rate and geometric mean titer for antibodies against diphtheria were significantly higher in the study group, whereas those against tetanus were significantly higher in the control group. However, all seroprotection rates against diphtheria and tetanus in the study and control groups were high: 100% against diphtheria and tetanus in the study group, and 98.7% against diphtheria and 100% against tetanus in the control group. No significant differences in the frequency of solicited and unsolicited adverse events were observed between the two vaccine groups. CONCLUSION: The new Td vaccine is highly immunogenic and safe, and this new Td vaccine can be effectively used for preventing diphtheria and tetanus.

Immunogenicity and safety assessment of a trivalent, inactivated split influenza vaccine in Korean children: Double-blind, randomized, active-controlled multicenter phase III clinical trial.

A multicenter, double-blind, randomized, active-control phase III clinical trial was performed to assess the immunogenicity and safety of a trivalent, inactivated split influenza vaccine. Korean children between the ages of 6 months and 18 y were enrolled and randomized into a study (study vaccine) or a control vaccine group (commercially available trivalent, inactivated split influenza vaccine) in a 5:1 ratio. Antibody responses were determined using hemagglutination inhibition assay, and post-vaccination immunogenicity was assessed based on seroconversion and seroprotection rates. For safety assessment, solicited local and systemic adverse events up to 28 d after vaccination and unsolicited adverse events up to 6 months after vaccination were evaluated. Immunogenicity was assessed in 337 and 68 children of the study and control groups. In the study vaccine group, seroconversion rates against influenza A/H1N1, A/H3N2, and B strains were 62.0% (95% CI: 56.8-67.2), 53.4% (95% CI: 48.1-58.7), and 54.9% (95% CI: 48.1-60.2), respectively. The corresponding seroprotection rates were 95.0% (95% CI: 92.6-97.3), 93.8% (95% CI: 91.2-96.4), and 95.3% (95% CI: 93.0-97.5). The lower 95% CI limits of the seroconversion and seroprotection rates were over 40% and 70%, respectively, against all strains. Seroconversion and seroprotection rates were not significantly different between the study and control vaccine groups. Furthermore, the frequencies of adverse events were not significantly different between the 2 vaccine groups, and no serious vaccination-related adverse events were noted. In conclusion, the study vaccine exhibited substantial immunogenicity and safety in Korean children and is expected to be clinically effective.