Both single-dose and two-dose meningococcal CRM-conjugate vaccine series (MenACWY-CRM) were immunogenic, but antibody responses were greater in patients after two doses, especially for patients aged 2-5 years old, according to a new study.
The multicenter, randomized, observer-blind, placebo-controlled study, conducted in the United States between October 2012 and May 2014, included 713 subjects who were up to date with their routine childhood immunizations. The subjects were broken into two age groups: children aged 2-5 years and children aged 6-10 years. The two age groups were randomized 1:1 to receive two doses of MenACWY-CRM or one dose of placebo followed by one dose of MenACWY-CRM, 2 months apart. Immunogenicity was measured using serum bactericidal activity with human complement.
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The researchers’ primary objective was to assess the noninferiority and superiority of antibody responses of the two doses, compared with the single dose against Neisseria meningitidis serogroups A,C, W, and Y, at 1-month after the last vaccination. Among the exclusion criteria for participation in the study were previous or suspected disease caused by N. meningitidis or immunization with any investigational or licensed vaccines containing meningococcal antigens.
Noninferiority of two doses of MenACWY-CRM, compared with a single dose, was demonstrated for all four serogroups. Additionally, at 1 month after the last vaccination, the superiority of receiving the two doses over the single dose was demonstrated for serogroups C and Y, for patients in the 2- to 5-year-old age cohort, while the superiority of two doses over one dose was demonstrated for the serogroup Y, for patients in the 6- to 10-year-old cohort.
The safety profile of the vaccine was similar in both groups. Medically attended adverse events that were considered to have been “possibly or probably related to the study vaccine” occurred in five subjects (as six events) in the 2- to 5-year-old age cohort and three subjects (as three events) in the 6- to 10-year-age cohort. One subject in the cohort aged 6-10 years withdrew from the study, because of vomiting and diarrhea, “which were considered to be unrelated to the study vaccine.” Eight serious adverse events were reported by five subjects, with one of the events “considered to be possibly related to the study vaccine.” That event was idiopathic thrombocytopenia, which occurred in a 6-year-old who received the single dose.
“[B]oth the single-dose and the two-dose primary series of MenACWY-CRM are immunogenic and have an acceptable safety profile in 2- to 10-year-old children. The two-dose primary series induced a higher immune response than [did] a single dose, although this difference in response decreases over time,” Dr. William Johnston Jr. of Alabama Clinical Therapeutics in Birmingham and his colleagues said.
Read the study in the Pediatric Infectious Disease Journal (doi: 10.1097/INF.0000000000000931).