Immunogenicity of a Reduced Meningococcal Vaccine Schedule in Infants

A randomized controlled trial comprising infants revealed a reduced schedule of a 4-component capsular group B meningococcal vaccine (4CMenB) was immunogenic and established immunologic memory after booster vaccination. The data regarding the 4CMenB vaccine, which is licensed as 4-dose infant schedule but was introduced in the United Kingdom as three doses at age 2, 4 and 12 months, was published in Open Forum Infectious Diseases. In this trial the immunogenicity and reactogenicity of the 2+1 schedule in infants was described.

Investigators randomly assigned 187 infants into either the test or control groups, with 94 and 93 infants in each group, respectively. Test group infants received the 4CMenB, along with their routine immunizations at age 2, 4 and 12 months, while controls received 4CMenB alone at age 6, 8 and 13 months.

In the test group, after primary and booster doses, the titers of a serum bactericidal antibody assay (SBA) against a serogroup B meningococcal reference strain (44/76-SL) were above the putative protective threshold (1:4) in 97% of participants. The SBA geometric mean titer postbooster (72.1; 95% CI, 51.7-100.4) was higher than the SBA geometric mean titer determined post-primary vaccination (48.6; 95% CI, 37.2-63.4). Compared with baseline controls, memory B cell responses after primary vaccinations did not change, but frequencies did significantly increase after the booster. Investigators also reported higher frequency of local and systemic adverse reactions associated to 4CMenB.

Investigators noted that there was limited availability of serum for the assessment of immunogenicity and for this reason only one reference strain, 44/56SL, was selected due to the importance of its antigenic composition.

In this study, the reduced schedule, when administered with other routine vaccinations, induced SBA titers above the putatively protective threshold against the reference strain. Assuming this threshold does correlate with protection, the data are in line with other effectiveness studies in the United Kingdom after the implementation of a reduced schedule. The geometric mean titer at 4 weeks after primary and booster doses for the same reference strain in this work were lower than reported in previous studies using the full licensed schedule.

The investigators highlighted that the clinical importance of a lower geometric mean titer is uncertain, especially in the context of documented effectiveness in the population of the United Kingdom. They added that, “consistent with previous work the use of 4CMenB was safe, with no [serious adverse events] reported to be related to the study vaccine administration,” and concluded that the data show, “a reduced infant 4CMenB schedule is safe, immunogenic and induces detectable immune memory after the booster dose.”

Reference

Pinto MV, O’Conner D, Gala U, et al. Immunogenicity and reactogenicity of a reduced schedule of a four-component capsular group B meningococcal vaccine (4CMenB): a randomised controlled trial in infants [published online April 29 2020]. Open Forum Infect Dis. doi:10.1093/ofid/ofaa143

This article originally appeared on Infectious Disease Advisor