Oral Presentation 25th International Pathogenic Neisseria Conference 2026

Immune responses following a 1-dose 4CMenB booster in adolescents primed as infants, and following a 2-dose series in naïve adolescents: a cross-study analysis. (141321)

Pavo Marijic 1 , Meike Adani 2 , Debasish Saha 3 , Laureano Mestra 2 , Allison Taylor Walker 4 , Tia Vincent 5 , Zeki Kocaata 1 , Federico Martinon-Torres 6 , Chiara Azzari 7 , Luca Moraschini 2 , Phil Watson 5
  1. GSK, Munich, Germany
  2. GSK, Siena, Italy
  3. GSK, Wavre, Belgium
  4. GSK, Rockville, Maryland, USA
  5. GSK, London, UK
  6. Genetics, Vaccines, Infections and Pediatrics Research group (GENVIP), Hospital Clínico Universitario de Santiago de Compostela, Santiago de Compostela, Spain
  7. Department of Pediatrics, University of Florence, Meyer Hospital, Florence, Italy

BACKGROUND
Immunogenicity and effectiveness of a 2-dose 4CMenB series in naïve adolescents have previously been demonstrated. Recent data show that a single 4CMenB booster in adolescents elicits anamnestic responses in those primed as infants.

AIM/METHODS
Immune responses after a 4CMenB booster dose in adolescents primed as infants (2+1 or 3+1) were evaluated alongside responses to a 2-dose series in naïve adolescents in previous clinical studies. Data were drawn and pooled from studies sharing key similarities: participants aged 10-20 years, recruited in Europe, identical MenB indicator strains and human serum bactericidal antibody assay (hSBA) methodology. Endpoints were hSBA titres ≥4 (seroprotection) and geometric mean titers (GMTs) measured 1 month post booster or post dose 2, for factor H-binding protein (fHbp), Neisseria adhesin A (Nad), neisserial heparin-binding antigen (NHBA), and porin A protein (PorA). Analyses included subgroups by age (10–15 years) and infant primary schedule (2+1).

RESULTS
A total of 234 primed participants receiving a 1-dose booster and 780 naïve participants receiving a 2-dose series were included; baseline characteristics and GMTs were similar across groups, with higher NadA GMTs in the primed group. In primed adolescents, seroprotection rates after booster were 87.9% (95% confidence interval [95% CI]: 83.0, 91.8) for fHbp, 99.1% (96.9, 99.9) for NadA, 85.7% (80.4, 89.9) for NHBA, and 70.7% (64.4, 76.5) for PorA. In naïve adolescents, seroprotection rates after dose 2 were 95.3% (93.5, 96.7), 100% (99.5, 100), 97.0% (95.4, 98.1), and 88.0% (85.4, 90.3), respectively. In a subgroup boosted at age 10–15 years, seroprotection rates were 93.1% (85.6, 97.4), 98.9% (93.8, 100), 93.0% (85.4, 97.4), and 75.9% (65.5, 84.4) for fHbp, NadA, NHBA, and PorA, respectively. In a subgroup primed with a 2+1 infant series, corresponding rates were 92.6% (83.7, 97.6), 98.5% (92.1, 100), 92.5% (83.4, 97.5), and 72.1% (59.9, 82.3). GMTs were generally high and similar between primed and naïve groups, with higher NadA GMTs in primed adolescents and similar patterns across subgroups.

CONCLUSIONS
The substantial proportion of primed adolescents achieving protective titers after a single 4CMenB booster dose suggests a degree of protection within the range observed for 2-dose series in naïve adolescents.