Antibody Persistence in Young Children 5 Years after Vaccination with a Combined Haemophilus influenzae Type b-Neisseria meningitidis Serogroup C Conjugate Vaccine Coadministered with Diphtheria-Tetanus-Acellular Pertussis-Based and Pneumococcal Conjugate Vaccines.

We evaluated antibody persistence in children up to 5 years after administration of a combined Haemophilus influenzae type b (Hib)-Neisseria meningitidis serogroup C (MenC)-tetanus toxoid (TT) conjugate vaccine coadministered with a pneumococcal conjugate vaccine. This is the follow-up study of a randomized trial (ClinicalTrials.gov registration no. NCT00334334/00463437) in which healthy children were vaccinated (primary vaccinations at 2, 4, and 6 months of age and booster vaccination at 11 to 18 months of age) with Hib-MenC-TT or a control MenC conjugate vaccine, coadministered with diphtheria-tetanus-acellular pertussis (DTPa)-based combination vaccines (DTPa/Hib for control groups) and a pneumococcal conjugate vaccine (10-valent pneumococcal nontypeable H. influenzae protein D conjugate vaccine [PHiD-CV] or 7-valent cross-reacting material 197 [CRM197] conjugate vaccine [7vCRM]). MenC antibody titers were measured with a serum bactericidal antibody (SBA) assay using rabbit complement (i.e., rabbit SBA [rSBA]), and antibodies against Hib polyribosylribitol phosphate (PRP) were measured with an enzyme-linked immunosorbent assay. Antibody persistence up to 5 years after booster vaccination is reported for 530 children ∼6 years of age. The percentages of children with seroprotective rSBA-MenC titers were between 24.2% and 40.1% in all groups approximately 5 years after booster vaccination. More than 98.5% of children in each group retained seroprotective anti-PRP concentrations. No vaccine-related serious adverse events and no events related to a lack of vaccine efficacy were reported. Approximately 5 years after booster vaccination, the majority of children retained seroprotective anti-PRP antibody concentrations. The percentage of children retaining seroprotective rSBA-MenC titers was low (≤40%), suggesting that a significant proportion of children may be unprotected against MenC disease. (This study has been registered at ClinicalTrials.gov under registration no. NCT00891176.).

Induction of immunologic memory following primary vaccination with the 10-valent pneumococcal nontypeable Haemophilus influenzae protein D conjugate vaccine in infants.

BACKGROUND: Induction of immunologic memory was assessed following primary vaccination with 10-valent pneumococcal nontypeable Haemophilus influenzae protein D conjugate vaccine (PHiD-CV). METHODS: Infants were randomized (1:1) to receive 3 doses of PHiD-CV or 7vCRM (7-valent CRM197-conjugated pneumococcal conjugate vaccine [PCV]) at 2, 3, and 4 months of age followed by 23-valent pneumococcal polysaccharide vaccine (23vPS) booster dose at 11 to 14 months of age. Pneumococcal geometric mean antibody concentrations (GMCs) and opsonophagocytic activity (OPA) geometric mean titers were measured. RESULTS: Postprimary immune responses were consistent with those in previous PHiD-CV and 7vCRM studies. Following 23vPS boosting, vaccine serotype-specific antibody GMCs increased 6.5- to 33.3-fold and 4.8- to 32.2-fold versus prebooster in the PHiD-CV and 7vCRM groups, respectively. Postbooster OPA titers increased 2.8- to 38.8-fold and 2.6- to 58.9-fold, respectively. Postbooster antibody GMCs exceeded postprimary levels but, for some serotypes, postbooster OPA geometric mean titers were lower than postprimary in both groups. An additional dose of the same PCV received for priming was administered to 52 children aged 46 to 50 months, resulting in higher responses versus postprimary vaccination for all serotypes, but not always higher than post-23vPS booster. CONCLUSIONS: Induction of immunologic memory following PHiD-CV priming was confirmed. Additional PCV boosting in 4-year-olds did not provide strong evidence of hyporesponsiveness induced by previous 23vPS boosting. However, our results did not rule out depletion of the memory B cell pool following 23vPS vaccination, resulting in subsequent attenuated immune responses, and therefore support the use of PCV rather than 23vPS for booster vaccination in the second year of life.

Immune memory to hepatitis B virus in 4-9-year old children vaccinated in infancy with four doses of hexavalent DTPa-HBV-IPV/Hib vaccine.

The combined hexavalent diphtheria-tetanus-acellular pertussis-hepatitis B-inactivated polio Haemophilus influenzae type b (DTPa-HBV-IPV/Hib) vaccine produces similar hepatitis B responses as the HBV monovalent vaccine. Booster vaccination of immunocompetent individuals primed against hepatitis B in infancy is currently not recommended. We investigated persisting immunity to hepatitis B in 4-6 (Study A; 106745) and 7-9 (Study B; 106744) year-old children primed in infancy and boosted in the second year of life with DTPa-HBV-IPV/Hib. Immunity was assessed by measuring persisting anti-HBs antibodies and evaluating the response to a challenge dose of HBV vaccine. At 4-6 years of age 86.0% of 186 subjects had persisting anti-HBs > or =10 mIU/ml increasing to 98.4% after the challenge. At 7-9 years of age, 78.0% of 186 subjects continued to have anti-HBs antibody concentrations > or =10 mIU/ml, increasing to 98.9% after the challenge. In both studies anti-HBs antibody GMC rose >80-fold. An anamnestic response to the HBV challenge was observed in 95.7% and 98.9% of subjects in Studies A and B, respectively. In both studies, 87% of 38 subjects with initially undetectable circulating anti-HBs antibodies (>3.3 IU/ml) achieved the 10 mIU/ml threshold after challenge; > or =97.0% of subjects with detectable antibodies before the challenge at least quadrupled their concentration. Post-vaccination anti-HBs concentrations were directly related to persisting antibody concentrations and the concentrations achieved after the booster dose in the second year of life. The HBV vaccine challenge dose was well tolerated. These studies show that primary and booster vaccination with combined DTPa-HBV-IPV/Hib (Infanrix hexa) induces sustained immune memory against hepatitis B up to age 9 years.

Persistence of antibodies in children primed with two different hexavalent diphtheria, tetanus, acellular pertussis, hepatitis B, inactivated poliovirus and Haemophilus influenzae type B vaccines and evaluation of booster vaccination.

This study assessed the persistence of antibodies following primary vaccination with two commercially available, hexavalent diphtheria, tetanus, acellular pertussis, hepatitis B, inactivated poliovirus and Haemophilus influenzae type b vaccines (Infanrix hexa and Hexavac). The immunogenicity and reactogenicity of booster vaccination with Infanrix hexa were also evaluated. A total of 329 children primed at 2, 4, and 6 months with Infanrix hexa (n=166) or Hexavac (n=163) received booster vaccination with Infanrix hexa at 12-19 months of age. Antibody concentrations were measured immediately before and 1 month after booster vaccination. Prebooster persistence of antibodies to HBs, PRP and poliovirus types was significantly higher in children primed with Infanrix hexa than with Hexavac, both in terms of seroprotection rate and GMCs/GMTs (p < 0.05). Boosting with Infanrix hexa elicited strong immune responses to all antigens irrespective of the primary vaccine used, with post-booster seroprotection rates comparable between the two primary vaccine groups (ranging from 98.1 to 100%). The incidence of clinically relevant solicited symptoms did not differ significantly between primary vaccine groups, even if the incidence of local symptoms appeared to be more frequent in subjects primed with Infanrix hexa than in those primed with Hexavac. In summary, booster vaccination with Infanrix hexa during the second year of life is immunogenic and well tolerated, offering protection irrespective of the primary combination vaccine used.