Immunogenicity and safety of two different Haemophilus influenzae type b conjugate vaccines in Korean infants

Immunogenicity and protective immunity against otitis media caused by pneumococcus in mice of Hib conjugate vaccine with PsaA protein carrier

This study evaluated the immunogenicity and protective immunity of a Hemophilus influenzae b (Hib) polysaccharide conjugate vaccine with the pneumococcal surface adhesin A (PsaA) protein carrier in young mice. The Hib polysaccharide was conjugated with the rPsaA protein carrier, which was produced using recombinant DNA technology. A total of 15 young mice aged 3 weeks to 5 weeks were immunized with the conjugate vaccine, and another 15 young mice of the same age were immunized with the licensed Hib-tetanus toxoid (TT) vaccine. Furthermore, the third group of 15 young mice was inoculated with phosphate buffer saline as control. The immunized mice were inoculated with pneumococcus in the middle ear. Results showed that IgG antibody responses against both the PsaA protein and Hib polysaccharide were observed in the Hib-PsaA group. However, no statistical difference was observed in the titer of IgG against the Hib polysaccharide between Hib-PsaA and Hib-TT groups. The elimination rate of pneumococcus and the inflammation of the middle ear showed the effectiveness of protective immunity against otitis media caused by pneumococcus. Our results suggest that the Hib polysaccharide can be successfully conjugated with rPsaA via amide condensation. This new Hib-PsaA conjugate vaccine can induce both anti-PsaA and anti-Hib immune responses in young mice and elicit effective protection against acute otitis media caused by pneumococcus.

A high throughput serum bactericidal assay for antibodies to Haemophilus influenzae type b

BACKGROUND

The protective capacities of antibodies induced with Haemophilus influenzae type b (Hib) vaccines can be directly assessed in vitro with a Hib-specific serum bactericidal assay (SBA). However, the conventional SBA requires several tedious steps including manual counting of bacterial colonies, and therefore, it is seldom used.

METHODS

To overcome these limitations, we have improved the conventional SBA by using frozen target bacteria and by developing an automated colony counting method based on agar plates with the chromogenic dye 2, 3, 5-triphenyl tetrazolium chloride (TTC).

RESULTS

These changes enabled us to analyze about 100 serum samples per day per person by SBA. When the intra- and inter-assay precisions were studied, this assay showed a coefficient of variation (CV) ranging from 1 to 38 %. To monitor the long term assay stability for assays involving different bacteria lots, complement lots, and operators, we analyzed bactericidal indices of quality control samples obtained over a 6 year period and found the CV to be about 35-50 %. Lastly, our SBA results were compared with the ELISA results obtained using 90 serum samples from children. We showed that the bactericidal index correlated with IgG anti-Hib antibody levels (r = 0.84), with a bactericidal index of 10 corresponding approximately to 0.15 μg/mL IgG, the widely accepted protective level of antibody.

CONCLUSION

We describe a simple high throughput SBA for anti-Hib antibodies that would be useful for evaluating various Hib vaccines. While additional work will be needed to standardize the assay, this SBA should greatly facilitate studies of Hib vaccines.

Safety reporting in developing country vaccine clinical trials-a systematic review

With more vaccines becoming available worldwide, vaccine research is on the rise in developing countries. To gain a better understanding of safety reporting from vaccine clinical research in developing countries, we conducted a systematic review in Medline and Embase (1989-2011) of published randomized clinical trials (RCTs) reporting safety outcomes with ≥50% developing country participation (PROSPERO systematic review registration number: CRD42012002025). Developing country vaccine RCTs were analyzed with respect to the number of participants, age groups studied, inclusion of safety information, number of reported adverse events following immunization (AEFI), type and duration of safety follow-up, use of standardized AEFI case definitions, grading of AEFI severity, and the reporting of levels of diagnostic certainty for AEFI. The systematic search yielded a total number of 50 randomized vaccine clinical trials investigating 12 different vaccines, most commonly rotavirus and malaria vaccines. In these trials, 94,459 AEFI were reported from 446,908 participants receiving 735,920 vaccine doses. All 50 RCTs mentioned safety outcomes with 70% using definitions for at least one AEFI. The most commonly defined AEFI was fever (27), followed by local (16) and systemic reactions (14). Logistic regression analysis revealed a positive correlation between the implementation of a fever case definition and the reporting rate for fever as an AEFI (p=0.027). Overall, 16 different definitions for fever and 7 different definitions for erythema were applied. Predefined AEFI case definitions by the Brighton Collaboration were used in only two out of 50 RCTs. The search was limited to RCTs published in English or German and may be missing studies published locally. The reported systematic review suggests room for improvement with respect to the harmonization of safety reporting from developing country vaccine clinical trials and the implementation of standardized case definitions.

Immunogenicity and safety of LBVH0101, a new Haemophilus influenzae type b tetanus toxoid conjugate vaccine, compared with Hiberix™ in Korean infants and children: a randomized trial

BACKGROUND

The World Health Organization (WHO) recommends that all countries adopt Haemophilus influenzae type b (Hib) vaccine into routine child immunization programs to protect children from the significant burden of life-threatening pneumonia and meningitis.

METHODS

In this blind, comparative, randomized, phase-III Korean multicenter study, we assessed immunogenicity and safety following primary vaccination of a new H. influenzae type b tetanus toxoid conjugate vaccine, LBVH0101 (LG Life Sciences, Ltd., Seoul, Korea) compared with Hiberix™ (GSK, Rixensart, Belgium) in Korean children at 2, 4 and 6 months of age followed by a booster vaccination at 12-15 months. Serum anti-PRP IgG concentration and bactericidal activity were determined. Local/systemic symptoms were assessed after vaccination. Serious adverse events were recorded throughout the study.

RESULTS

A total of 185 infants were included in immunogenicity evaluations. After the second and third doses of LBVH0101, 90.32% and 100% of infants achieved an antibody level ≥1 μg/mL, respectively, compared with 78.26% and 96.74% of those who received Hiberix™. After the second vaccination, the geometric mean concentration (GMC) of LBVH0101 recipients was 7.34 μg/mL and was higher than that of Hiberix™ recipients (3.55 μg/mL). After the third vaccination, the GMCs were 14.59 μg/mL and 12.15 μg/mL in the LBVH0101 and Hiberix™ recipients, respectively. The booster dose produced higher antibody concentrations: 30.25 μg/mL and 71.64 μg/mL for LBVH0101 and Hiberix™ recipients, respectively. Bactericidal capacity and antibody potency of anti-PRP IgG induced by LBVH0101 was 35.05 and 116.27 after the second and third vaccinations, respectively, compared with 53.76 and 79.64 for Hiberix™. Anti-PRP IgG seroprotection rate and GMC were similar post-primary immunization between the groups; both showed functional maturation and similar booster responses. LBVH0101 had comparable safety results as the control vaccine, Hiberix™, as most of the solicited adverse events and unsolicited adverse events upon LBVH0101 administration were mild in severity. No serious vaccination-related adverse reactions were observed.

CONCLUSIONS

LBVH0101 showed a good immunogenicity and safety profile in infants and children. The two-dose infant-priming schedule with a booster dose may suffice for Hib immunization in Korean infants (Clinical trial registration numbers: NCT01019772 and NCT01251133).

Mortality from bacterial meningitis in children in Kosovo

Bacterial meningitis is a severe infection responsible for high mortality. This prospective study of 277 pediatric bacterial meningitis cases was done to identify factors predicting death in children <16 years of age living and treated in a limited-resources country (Kosovo). Of the 277 children enrolled, 60 patients (22%) developed neurologic complications, and 15 children died (5%). The following variables were strongly correlated with mortality: altered mental status on admission (relative risk [RR] = 29.9), presentation of the initial cerebrospinal fluid as thick pus (RR = 29.9), prehospital seizures (RR = 23.5) and their recurrence >24 hours after admission (RR = 11.5), age <1 month (RR = 19.3), the use of inotropic agents (RR = 11.5), and admission after 5 days' duration of illness (P < .001). The mortality rate in children in Kosovo is similar to those reported from developing countries, and this is most likely due to the unfavorable living conditions.

A comparative study to evaluate the safety and immunogenicity of two lots of Haemophilus influenzae type-B conjugate vaccine manufactured at different scales

OBJECTIVE

To compare the immunogenicity and safety of two different lots of SII Haemophilus influenzae type-B-tetanus toxoid conjugate (SII HibP(RO)) vaccine manufactured at different scales when given in 3-dose schedule.

DESIGN

Phase IV, open label, comparative, randomized parallel group study.

SETTING

Shirdi Sai Baba Hospital, Vadu Budruk, Pune and Pediatrics Department of King Edward Memorial Hospital Research Centre, Pune.

SUBJECTS

204 normal healthy infants of age 6-8 weeks at the time of first vaccination.

METHODS

The eligible subjects received 3 doses of 0.5 ml of SII HibP(RO) vaccine of either lot depending upon randomization number, intramuscularly in right thigh in the EPI schedule of 6, 10 and 14 weeks. They also received concomitantly DTP-HB vaccine intramuscularly on left thigh and Oral Polio vaccine (OPV). Solicited reactions were captured for 7 days following each vaccination; the events beyond 7 days till day 28 were captured as unsolicited adverse events. Serious Adverse Events (SAEs) were looked for throughout the subject participation. Blood samples were collected at baseline (before the first dose) and one month after the third dose for anti-PRP (polyribosylribitol phosphate) antibodies.

RESULTS

In both groups, more than 98% subjects achieved short-term seroprotection (anti-PRP ≥ 0.15 μg/ml) after 3 doses. The long-term seroprotection (anti-PRP ≥ 1 μg/ml) was 87% and 80% in infants receiving lot manufactured at industrial scale and small scale respectively. Short and long term seroprotection and GMTs increased significantly as compared to baseline in both the groups. Overall local pain (52% and 58%), redness (30% and 41%), swelling (34% and 44%), fever (6% and 6%) and irritability (52% and 50%) were reported in infants receiving lot manufactured at industrial scale and small scale respectively. Majority of the reactions were mild and resolved without any sequelae. Four SAEs, none of them causally related to the study vaccine, occurred during study.

CONCLUSION

SII HibP(RO) vaccines manufactured in small and industrial scale are equally immunogenic, safe and confer adequate seroprotection to infants of 6-14 weeks of age. Scaling up production process has not affected the safety and immune response in the target population.

The causative organisms of bacterial meningitis in Korean children in 1996-2005

Bacterial meningitis remains a serious cause of morbidity and mortality in childhood, despite the availability of effective vaccines against Haemophilus influenzae type b (Hib) or Streptococcus pneumoniae. The purpose of this study was to analyze data on bacterial meningitis cases in Korea from 1996 through 2005. The information of all hospitalized bacteria-proven meningitis cases was obtained from 17 university hospitals nationwide. A total of 402 cases were identified. Of these, 125 (29.9%) cases were neonates. Streptococcus agalactiae was the most common bacteria responsible for 99 (24.6%) of all cases regardless of age, followed by S. pneumoniae for 91 (22.6%) and H. influenzae for 67 (16.7%) patients. The common etiology beyond the neonatal period was S. pneumoniae for 91 (33.0%) followed by H. influenzae for 63 (22.8%) patients. The overall case fatality rate was 9.4%, which was similar with that in 1986-1995. In conclusion, S. agalactiae, S. pneumoniae and H. influenzae were important etiologic agents of bacterial meningitis in children in the last 10 yrs. It is required to establish the preventive strategy of the three bacteria. The nationwide epidemiologic study should be continued to evaluate immunization strategy and efficacy.

Immunogenicity of Haemophilus influenzae type b conjugate vaccines in Korean infants: a meta-analysis

A meta-analysis was performed on the immunogenicity of Haemophilus influenzae type b (Hib) conjugate vaccines after 2 (2 and 4 months) and 3 doses (2, 4, and 6 months) in Korean infants. A database search of MEDLINE, KoreaMed, and Korean Medical Database was done. The primary outcome measure was the proportion of infants with anti-polyribosylribitol phosphate (PRP) concentrations > or =1.0 microg/mL. Eight studies including eleven trials were retrieved. One trial reported on the diphtheria toxoid conjugate vaccine (PRP-D) and 2 trials each on the mutant diphtheria toxin (PRP-CRM) and Neisseria meningitidis outer-membrane protein (PRP-OMP) conjugate vaccine. Heterogeneity in study designs between trials on PRP-CRM was noted and one trial reported on a monovalent and another on a combination PRP-OMP vaccine. Thus, a meta-analysis was conducted only on the tetanus toxoid conjugate vaccine (PRP-T). After a primary series of 2 doses and 3 doses, 80.6% (95% confidence interval [CI]; 76.0-85.1%) and 95.7% (95% CI; 94.0-98.0%) of infants achieved an antibody level > or =1.0 microg/mL, respectively. The immunogenic response to the PRP-T vaccine was acceptable after a primary series of 3 doses and also 2 doses. A reduced number of doses as a primary series could be carefully considered in Korean infants.