Immunogenicity and safety of a meningococcal serogroups A and C tetanus toxoid conjugate vaccine (MenAC-TT): two immune schedules in toddles aged 12-23 months in China

Abstract

Background: This exploratory study aimed to assess the immunogenicity and safety of 1 and 2 doses of meningococcal serogroups A and C tetanus toxoid-conjugate vaccine (MenAC-TT) in toddles.Methods: Healthy participants aged 12-23 months were randomized into two groups to receive 1 or 2 doses of the tested vaccine. The interval was 28 days between two doses. Blood samples were collected at day 0 before the immunization and day 28 post-each dose. Safety observation was conducted during 28 days after each vaccination. Serious adverse event (SAE) was conducted throughout 6 month observation period.Results: Overall 301 toddles were vaccinated. Twenty-eight days post full-course vaccination, ≥97.20% toddles had titers ≥1:8 and ≥81.48% had titers ≥1:128 for MenA and MenC in the two schedules groups. There were no significant differences between the two schedule groups for each titer thresholds and serogroups. Up to month 12 post the first dose, titers ≥1:8 and 1:128 were declined to 71.32-80.83% and 26.67-57.85% for each meningococcal serogroups. Most adverse reactions (ARs) were mild or moderate, and the incidence of grade 3 ARs was below 3.33%. The incidence of redness was significantly higher in the two doses group than that in the one dose group, in terms of grade 1 and grade 2 were higher. No SAEs were considered causally related to vaccination.Conclusion: The MenAC-TT showed similarly safety and immunogenicity profile in toddles with two schedules. It will be more important to provide the data for formulating appropriate immunization strategies in different age groups in China.

Trial registration: ClinicalTrials.gov NCT03714737.

Keywords: Meningococcal conjugate vaccine; clinical trial; immunogenicity; safety.

Figures

Figure 1.

Flow chart for the recruitment of volunteers in the study. Titers for antibody to MenA≥1:8 pre-vaccination were two participants in the one and two doses group, respectively. Titers for antibody to MenC ≥1:8 pre-vaccination were three participants in the one and two doses group, respectively. They were removed from the analysis set (mPPS) for immunogenicity.