Children with Haemophilus influenzae type b (Hib) vaccine failure have long-term bactericidal antibodies against virulent Hib strains with multiple capsular loci.
Children who develop invasive Haemophilus influenzae serotype b (Hib) disease after immunisation with a highly-effective conjugate vaccine are more likely to have been infected with Hib strains possessing multiple copies of the capsulation locus. Using a recently-validated serum bactericidal antibody (SBA) assay, we tested convalescent sera from 127 Hib vaccine failure cases against clinical Hib strains expressing 1-5 copies of the capsulation locus. SBA titres correlated weakly with anti-capsular IgG antibody concentrations and there was no association between SBA geometric mean titres and number of capsulation locus copies. After infection, children with Hib vaccine failure were equally protected against Hib strains with 1-5 copies of the capsulation locus.
Vaccine Evaluation Unit, Public Health England, Clinical Sciences Building, Manchester Royal Infirmary, Manchester, UK.
Kelly
K
Townsend-Payne
Immunisation Hepatitis and Blood Safety Department, Centre for Infectious Disease Surveillance and Control, Public Health England, Colindale, London, UK; Paediatric Infectious Diseases Research Group, St. George's University of London, London, UK. Electronic address: shamez.ladhani@phe.gov.uk.
Shamez N
SN
Ladhani
Vaccine Evaluation Unit, Public Health England, Clinical Sciences Building, Manchester Royal Infirmary, Manchester, UK.
Helen
H
Findlow
Institute of Hygiene and Microbiology, University of Wuerzburg, Germany; Department of Medicine, Griffith University, Queensland, Australia.
Mary
M
Slack
Vaccine Evaluation Unit, Public Health England, Clinical Sciences Building, Manchester Royal Infirmary, Manchester, UK; Inflammation Sciences Research Group, University of Manchester, School of Translational Medicine, Stopford Building, Manchester, UK.
Ray
R
Borrow
D000907:Antibodies, Bacterial / Q000097:blood*; D016667:Bacterial Capsules; D002675:Child, Preschool; D006192:Haemophilus Infections / Q000517:prevention & control*; D018073:Haemophilus Vaccines / Q000627:therapeutic use*; D019741:Haemophilus influenzae type b; D006801:Humans; D007074:Immunoglobulin G / Q000097:blood; D007223:Infant; D058248:Serum Bactericidal Antibody Assay; D017211:Treatment Failure; D018074:Vaccines, Conjugate / Q000627:therapeutic use
D000907:Antibodies, Bacterial; D018073:Haemophilus Vaccines; C044237:Haemophilus influenzae type b polysaccharide vaccine; D007074:Immunoglobulin G; D018074:Vaccines, Conjugate
Capsular operon; Failure; Haemophilus influenzae type b; Vaccine