Effective and tolerable vaccination is an essential strategy to prevent Japanese encephalitis (JE) in endemic areas. Graphical Abstract type b conjugate vaccine and pneumococcal conjugate vaccine at 12 to15 months of age, and diphtheria, tetanus, acellular pertussis (DTaP) vaccine at 15 to 18 months of age, as long as doses were given at least 8 days after and at least 4 weeks before a dose of the study vaccine. Measles, mumps, rubella (MMR) and varicella vaccines were allowed if administered at least 4 weeks before or after administration of the study vaccine. Study vaccine LAJEV (CD-JEVAX?, Chengdu Institute of Biological Products, Chengdu, China) was used in this study. The main component of this vaccine is usually SA14-14-2 strain of JE computer virus. The others are lactose, sucrose, gelatin, human blood albumin and urea. Each subject was administered 0.5 mL of freshly reconstituted vaccine subcutaneously to the upper arm as instructed by the manufacturer. Immunogenicity evaluation Blood samples for immunogenicity assays were taken prior to and 4-6 weeks after each vaccination. The samples were kept frozen at -70 and were sent to the central laboratory of the Korean National Institute of Health. Sera were tested for neutralizing antibodies using the plaque reduction neutralization test (PRNT) as followings. Test sera were heat-inactivated at 56 for 30 min and diluted 1:5 and in serial two fold dilutions (up to 1 1:2,560). The Nakayama strain (heterologous SA-14-14 strain) was diluted in phosphate buffer saline made up of 5% fetal calf serum and 5% guinea pig match to provide 200 pfu/0.1 mL, and added in equivalent volume to each serum dilution. Serum-virus mixtures were incubated over-night at 48 and added Navarixin to drained baby hamster kidney 21 cell culture monolayers produced in six well plates. After adsorption for one Navarixin hour at 37, the monolayers were overlaid with semisolid medium. Approximately 5 days later, when plaques could be seen microscopically, the medium was removed. The complete titration of each serum was carried out in a single test (14). The end point for neutralization was the highest dilution of serum reducing plaques by 50% of the JE challenge virus, compared with a negative serum Navarixin control. JE neutralizing antibody titer 10 was considered seropositive and seroprotective (15). Security evaluation After vaccination, a physician monitored subjects for any immediate sign or symptom of local and/or systemic reactions for at least 30 min. We asked the parents or legal guardians to record any adverse reactions occurred from days 0-42 after vaccination. Significant local reaction was defined as redness >2.5 cm, swelling >2.5 cm, or tenderness, or crying and protesting when the injection site was touched. Systemic reactions included vomiting, diarrhea, irritability, drowsiness, loss of appetite, shivering, or fever. Fever was defined as a heat 38 (100.4F) (16). Symptoms were defined as being related if there was a reasonable possibility that this vaccine contributed to the adverse event. Unsolicited Navarixin local or systemic reactions (with onset date, intensity and resolution) were recorded throughout the 42-day period after each vaccination. Severe adverse events were reported for the duration of the study. Blood pressure, pulse, Navarixin and body temperature of all subjects were recorded at every visit, and physical examinations were performed. Statistical analysis Itgb7 Based on the premise of a 98% production rate of seroprotective antibody, a 10% allowable error for the trial and 10% level of significance, the minimum necessary quantity of subjects was found to be 65 in this study. Immunogenic response was assessed by the percentage of subjects with seroprotective neutralizing antibody titer and by calculation of the.