Group ACYW135 meningococcal polysaccharide vaccine(Walvax Biotechnology Co., Ltd.)

This is a phase IV, single-center, observer-blind, randomized, controlled vaccine trial in 2 to 10 years old healthy subjects. Each participant will receive a single intramuscular injection of one of the two vaccines either MPV ACYW® vaccine or Menactra ® vaccine according to the vaccine group assignment and will be followed up for one month for immunogenicity evaluation and for 6 months for safety evaluation.
Statistical Hypothesis:
H0: Seroconversion rate of test group is inferior to that of control group HA: Seroconversion rate of test group is non-inferior to that of control group Sample size calculation: the sample size was calculated based on non-inferiority test with alpha level of 0.025 and 80% power, assuming seroconversion rate in control group was 95% with non-inferiority margin at 10%. The sample size required for the study is 124 per arm. After adjusting for 5% drop-out, the final sample size required is 130 per arm.