Pooled-sera hSBA titres predict individual seroprotection in infants and toddlers vaccinated with 4CMenB

Abstract The Serum Bactericidal Antibody assay with human complement (hSBA) using individual immune sera is a surrogate of protection for meningococcal vaccines. Strain coverage of 4CMenB, a licensed vaccine against serogroup B meningococcal (MenB) disease, has been extensively assessed in hSBA using pooled sera, directly or through the Meningococcal Antigen Typing System (MATS). The extent to which pooled-sera hSBA titres reflect individual protection is not yet fully understood. We analysed more than 17000 individual hSBA titres from infants and toddlers vaccinated with 4CMenB, pooled-serum hSBA titres from subsets therein and MATS data from a 40 strain panel representative of invasive MenB disease in England and Wales. Individual hSBA titres segregated in two normal distributions, respectively from responding and non-responding subjects (fit_model-data: r  = 0.996, p -values r  = 0.97, p -value We identified a robust mathematical relationship between the mean of individual hSBA titres and the proportion of subjects achieving a protective titre (seroprotection rate, r  = 0.95, p -value Finally, strains defined covered by MATS had on average 77% predicted seroprotection rate (interquartile range, IQR: 66–100%) and 39% for non-covered strains (IQR: 19–46%). We conclude that seroprotection rates in infants and toddlers vaccinated with 4CMenB can be accurately predicted by pooled-serum hSBA, and that strain coverage defined by MATS is associated with high seroprotection rates. Summary The Serum Bactericidal Antibody assay (SBA) from individual sera is a surrogate of protection for meningococcal vaccines. We show that SBA performed on pooled sera predicts individual protection.