The purpose of this preliminary study was to evaluate the immunogenicity and safety of 1 and 2 doses of meningococcal serogroups A and C tetanus toxoid-conjugate vaccine (MenAC-TT) in toddlers. Healthy individuals aged 12–23 months were randomly assigned to one of two groups and given either one or two doses of the tested vaccination. The gap between two dosages was 28 days. Blood samples were taken on day 0 before the vaccination and on day 28 after each dosage. Each vaccine was followed by a safety check 28 days later. Throughout the 6-month monitoring period, serious adverse events (SAE) were recorded. In all, 301 toddles were immunized. Twenty-eight days after the entire course of immunization, 97.20 percent of the toddlers had titers 1:8 and 81.48 percent had titers 1:128 for MenA and MenC in the two scheduling groups. There were no significant changes in titer thresholds or serogroups between the two schedule groups. The majority of adverse reactions (ARs) were mild or moderate, and the prevalence of grade 3 ARs was less than 3.33 percent. In terms of grade 1 and grade 2, the incidence of redness was considerably greater in the two doses group than in the one dosage group. There were no SAEs that were thought to be caused by immunization.

In toddlers with two regimens, the MenAC-TT demonstrated a similar safety and immunogenicity profile. It will be more necessary to give data for China to develop suitable vaccination policies for different age groups.