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PubMed2005

Immunogenicity of one, two or three doses of a meningococcal C conjugate vaccine conjugated to tetanus toxoid, given as a three-dose primary vaccination course in UK infants at 2, 3 and 4 months of age with acellular pertussis-containing DTP/Hib vaccine.

Reduction of the number of injections necessary to confer protection in the infant schedule would reduce discomfort, improve cost-effectiveness and create space for the addition of new vaccinations in the future. This study assessed the immunogenicity of one, two or three doses of meningococcal C conjugate vaccine conjugated to tetanus toxoid (MCC-TT) [Neis-VacC] given concomitantly with a combined diphtheria/tetanus/acellular pertussis/Haemophilus influenzae type b -TT conjugate (DTaP-Hib-TT) [Infanrix-Hib] vaccine at 2, 3 and 4 months of age. A total of 106 healthy UK infants were enrolled and randomised into two groups, one in which blood was taken after the first and third dose and the other after the second and third dose. The meningococcal serogroup C serum bactericidal antibody (SBA) geometric mean titre (GMT) rose significantly from post-first dose (491, 95% CI 275, 877) to post-second dose (1052, 95% CI 774, 1433) (p=0.03), with no significant change after the third dose (1024, 95% CI 768, 1366). An SBA titre of >or=8 was achieved by 92% after the first dose and 100% after the second and third doses. The Hib IgG geometric mean concentration (GMC) rose significantly after each dose: post-first (0.14 microg/ml 95% CI 0.10, 0.18), post-second (0.54 microg/ml, 95% CI 0.33, 0.90), post-third (2.04 microg/ml, 95% CI 1.52, 2.74). The Hib GMC after the third dose was higher than reported previously when this DTaP/Hib was given either on its own or concomitantly with a MCC-CRM conjugate vaccine according to the UK 2, 3 and 4 month schedule. This suggests some enhancement of the response to a Hib-TT vaccine by concomitant administration of MCC-TT. These results suggest that a reduced number of doses of MCC-TT would be adequate in infancy if given concomitantly with an acellular pertussis-containing vaccine.

Antibodies, Bacterial↗

PubMed2000

Safety and immunogenicity of heptavalent pneumococcal vaccine conjugated to CRM(197) among infants with sickle cell disease. Pneumococcal Conjugate Vaccine Study Group.

OBJECTIVES: To determine the immunogenicity and safety of heptavalent pneumococcal polysaccharide vaccine (serotypes 4, 6B, 9V, 14, 18C, 19F, and 23F) conjugated to CRM(197) (7-valent conjugate pneumococcal vaccine [7VPnC]) among infants with sickle cell disease (SCD) and a comparison group of infants without SCD (non-SCD). DESIGN: Two cohorts of infants were enrolled and received open-label doses of 7VPnC vaccine; infants enrolled before 2 months of age received 7VPnC vaccine at 2, 4, and 6 months of age followed by 23-valent pneumococcal polysaccharide vaccine (PS-23) at 24 months of age for those infants with SCD (schedule A), and infants enrolled between 2 and 12 months of age received 7VPnC at 12 months of age followed by PS-23 at 24 months of age for infants with SCD (schedule B). Safety data were collected for 3 days after each dose of vaccine. Antibody concentrations were measured to each of the 7VPnC serotypes by enzyme-linked immunosorbent assay before each vaccine dose and 1 month after the last 7VPnC dose and the PS-23 vaccine dose. RESULTS: Forty-five infants (34 SCD and 11 non-SCD) were vaccinated according to schedule A and 16 infants (13 SCD and 3 non-SCD) according to schedule B. The 7VPnC vaccine was highly immunogenic for all serotypes among infants with and without SCD who received 3 doses of vaccine according to schedule A: depending on serotype, 89% to 100% achieved antibody concentrations above.15 microg/mL and 56% to 100% achieved antibody concentrations above 1.0 microg/mL. Among infants immunized according to schedule B, a single dose of 7VPnC vaccine resulted in antibody concentrations above.15 microg/mL in 53% to 92% by serotype and above 1.0 microg/mL in 31% to 71% by serotype. A single dose of PS-23 resulted in dramatic increases in the antibody concentrations to all serotypes regardless of 1- or 3-dose priming. There was no difference in the reactogenicity of the 7VPnC vaccine between those with and without SCD. There were no serious reactions to the 7VPnC or PS-23 vaccines, even among those with high antibody concentrations before immunization. CONCLUSIONS: Infants with SCD respond to 7VPnC vaccine with antibody concentrations that are at least as high as infants without SCD. Infants immunized with 7VPnC vaccine at 2, 4, and 6 months of age developed antibody concentrations in the same range as those achieved among infants without SCD enrolled in a large trial that demonstrated vaccine efficacy against invasive disease. Significant rises were seen in antibody concentrations to all 7VPnC serotypes after the PS-23 booster in children receiving schedule A or B.

Anemia, Sickle Cell↗

PubMed2002

Evolution of conjugate vaccines.

Conjugate vaccines--bacterial polysaccharides conjugated to proteins to improve their immunizing properties--have been a success story since their introduction less than 20 years ago. The Haemophilus influenzae type b conjugate vaccine has nearly eliminated invasive Haemophilus influenzae type b disease in large parts of the world. The key reasons for its success are its ability to induce immunologic memory and reduce asymptomatic carriage, hence the spread of infection. The first pneumococcal conjugate vaccine was licensed in 2000 and is already in wide demand in the USA. The first meningococcal conjugate vaccine was introduced in a nationwide program in the UK in 1999. Current discussion focuses on the efficacy of the conjugate vaccines for different end-points and the cost-effectiveness of their use globally.

Adult↗

PubMed2003

Conjugate vaccines.

Conjugate vaccines in which the capsular polysaccharide of Haemophilus influenzae type b, common serotypes of Streptococcus pneumoniae and group C Neisseria meningitidis are covalently bound to a protein antigen to convert a T-cell-independent immune response into a T-cell-dependent response have proved highly effective in the prevention of invasive disease in infants and young children. This review looks at what has been learnt from developing these vaccines that could be useful for the clinical development of future conjugate vaccines, in such areas as combination vaccines, dose-ranging, cross-protection of closely related antigens, prevention of noninvasive disease, correlates of protection and use in older age groups. In addition, a wide range of other organisms may be susceptible to conjugate vaccines and new indications and approaches are considered. This will be a highly active area for many years to come.

Child↗

PubMed2002

[Conjugated vaccines].

Conjugate vaccines extend the vaccinal prevention for children to more diseases. Conjugating the capsular polysaccharide to a carrier protein transforms a T-independent antigen in a T-dependent, allowing protection of the children (before 2 years of age) against Haemophilus influenzae type b, meningococcal C and pneumococcal infections. This article reviews the 3 conjugate vaccines and their results with focus on some questions: antigens interference in the immunological response, serological subrogate for protection, herd immunity and replacement of circulating serotypes.

B-Lymphocytes↗

PubMedDate not supplied

[Conjugate vaccines].

Haemophilus Infections↗

PubMed2002

[Conjugate vaccines].

Adult↗

PubMed1991

Immunoglobulin deficiency and idiotype expression in children developing Haemophilus influenzae type b disease after vaccination with conjugate vaccine. The Collaborative Study Group.

OBJECTIVE: --Haemophilus influenzae type b (Hib) conjugate vaccines are effective in preventing Haemophilus disease in most children. The reasons why the vaccination fails in some children are unknown. This study investigated host factors in children who developed the disease despite conjugate vaccination. DESIGN, PATIENTS, OUTCOME MEASURES:--A convenience sample of 23 patients in whom Hib disease developed 14 days or more after conjugate vaccination was investigated for the presence of subnormal serum immunoglobulin concentrations and anticapsular antibody responses to Hib disease. We also investigated expression of the Hib idiotype 1 (Hibld-1), a serological marker of a VKII chain that comprises a major portion of the normal variable region repertoire of the antibody response to Hib polysaccharide. The results were compared with those of 149 patients in whom the unconjugated Hib polysaccharide vaccine failed and of 90 unvaccinated patients who developed the disease. RESULTS: --Compared with children in whom the unconjugated polysaccharide vaccination failed, the relative risk of a subnormal serum concentration of IgM, IgA, IgG, and/or IgG2 in the children in whom the conjugate vaccination failed was 4.9 (95% confidence interval [CI], 1.8 to 14; P less than .003) and of IgG2 was 22 (95% CI, 3.5 to 146; P less than .001). With the exception of the children with subnormal serum immunoglobulin concentrations, most of the children with conjugate vaccination failure showed normal or high anticapsular antibody responses to the disease, whereas the children with polysaccharide vaccination failure showed impaired responses. The Hibld-1 was expressed by the majority of the children in both vaccination failure groups and of the unvaccinated patients. CONCLUSIONS: --In most patients, vaccination failure is not attributable to lack of expression of the variable region gene encoding Hibld-1. However, children in whom conjugate vaccination has failed frequently have subnormal serum immunoglobulin concentrations and should be evaluated for immunodeficiency.

Antibodies, Bacterial↗

PubMedDate not supplied

Early immunization with conjugate vaccines.

Conjugate vaccines have been used during the neonatal period or in early infancy in order to test their safety and immunologic behaviour. Adverse events even in neonates and premature babies have been mild and spontaneously resolving. Anticapsular antibody concentrations after first doses of Hib conjugates in early infancy are generally low, but analysis of responses clearly demonstrates active antibody production. Concentrations after the whole primary series are at or close to the level achieved in routine vaccination programmes. Noteworthy, immunologic memory seems to be induced already by first doses during newborn period. These data suggest that protection against invasive Hib infections may be achieved early in life.

Bacterial Capsules↗

PubMed2006

Breastfeeding enhances the antibody response to Hib and Pneumococcal serotype 6B and 14 after vaccination with conjugate vaccines.

BACKGROUND: This study was performed in order to investigate the relationship between breastfeeding and the antibody response after vaccination with conjugate vaccines against Hib and pneumococcal diseases. METHODS: This was an open non-randomised multi-centre study enrolling 101 healthy Swedish infants. PncCRM was administered concomitantly with DTaP/IPV/Hib at 3, 5, and 12 months at separate site. Duration of breastfeeding was calculated for days of almost exclusive as well as of total (any form of) breastfeeding. RESULTS: At 13 months of age 6 out of 83 children did not reach 0.2mug/ml against serotype 6B, and five of these were breastfed less than 90 days (Fisher's Exact test, P=0.011). Four children did not reach 1mug/ml against Hib and all those were breastfed less than 90 days (Fisher's Exact test, P=0.008). One month after the second dose, at 6 months of age, children breastfed 90 days or more showed significantly higher GMC against serotype 14 (P=0.003). CONCLUSION: This study indicates that children exclusively breastfed 90 days or more might get a better serological protection against Hib, and the pneumococcal serotypes 6B and 14 after vaccination, compared to children less breastfed.

Antibodies, Bacterial↗

PubMed2000

Serum opsonic activity in infants with sickle-cell disease immunized with pneumococcal polysaccharide protein conjugate vaccine. The Pneumococcal Conjugate Vaccine Study Group.

Pneumococcal infections are an important cause of morbidity and mortality in children with sickle-cell disease (SCD). Pneumococcal conjugate vaccines (PCVs) are immunogenic in healthy infants <2 years of age but have not been evaluated in young children with SCD. Infants with SCD were immunized with a 7-valent PCV (Wyeth-Lederle Vaccines & Pediatrics) at 2, 4, and 6 months of age. A booster dose of 23-valent pneumococcal polysaccharide vaccine (PPV; Pnu-Immune) was administered at 24 months of age. Antipneumococcal type 6B and 14 serum opsonic activity was measured to assess the biologic function of the antibody. Following the administration of three doses of PCV, opsonic activity against serotype 6B increased from 4. 8% at 2 months to 33.5% at 7 months, with a subsequent decline to 8.1% at 12 months and 7.5% at 24 months and with an increase to 30.7% at 25 months after administration of a booster dose of PPV. Similar trends were seen with serotype 14 (opsonic activities were 9.4% at 2 months, 24.9% at 7 months, 16.5% at 12 months, and 12.6% at 24 months, and the opsonic activity was 27.3% 1 month after the administration of PPV). Serum opsonic activity correlated with antibody levels for both serotypes. PCV induces serum opsonic activity in infants with SCD. Antipneumococcal serum opsonic activity correlates with antibody levels.

Anemia, Sickle Cell↗

PubMed1995

Serotype distribution of Streptococcus pneumoniae infections among preschool children in the United States, 1978-1994: implications for development of a conjugate vaccine.

Conjugation of pneumococcal polysaccharide antigens to a protein carrier may improve protective immunity after vaccination of young children, an age group with high incidence of Streptococcus pneumoniae infection and poor immune responses to polysaccharide vaccines. To identify serotypes most commonly associated with infection in young children, pneumococcal isolates were serotyped from 3884 children < 6 years old (including 3007 < 2 years old) with pneumococcal bacteremia (n = 3169), meningitis (n = 401), or otitis media (n = 314). The isolates were submitted as part of a national surveillance during 1978-1994. Seven serotypes (14, 6B, 19F, 18C, 23F, 4, and 9V) accounted for 3045 isolates (78%). A conjugate pneumococcal vaccine protecting against these seven serotypes and serologically cross-reactive serotypes could potentially prevent 86% of bacteremia and 83% of meningitis but only 65% of otitis media cases. The proportion of isolates covered by such a vaccine increased from 78% to 87% during 1978-1994. Surveillance for pneumococcal serotypes causing infection is needed to detect shifts in serotype distribution over time.

Bacterial Vaccines↗

PubMed2002

The potential of pneumococcal conjugate vaccines for children.

In contrast to earlier pneumococcal vaccines, conjugate vaccines hold promise for reducing pneumococcal morbidity and mortality in infants and young children. The first commercially available conjugate vaccine formulation, which targets seven serotypes, was licensed in the US and other countries in 2000; this vaccine is now part of routine infant immunization in the US. Demand has been high and greater than vaccine supply. Clinical trials indicate that conjugate vaccines are highly efficacious against invasive pneumococcal disease and modestly efficacious against otitis media and pneumonia. In carriage studies conjugate vaccines reduced vaccine-type carriage but led to an increase in carriage of other serotypes. Remaining questions include whether less frequent transmission of vaccine serotypes will mean less disease in unvaccinated children and adults or if nonvaccine serotypes will begin to cause more disease. Monitoring disease burden after widespread use in the US is critical for understanding the effects of the vaccine. In addition making pneumococcal vaccines available for children in developing countries should be a high priority.

Bacteremia↗

PubMed1986

Induction of meningococcal group B polysaccharide-specific IgG antibodies in mice by using an N-propionylated B polysaccharide-tetanus toxoid conjugate vaccine.

Conjugation of the group B meningococcal polysaccharide to tetanus toxoid failed to substantially enhance its immunogenicity in mice. Therefore, additional chemical manipulation of the basic structure of the group B meningococcal polysaccharide was attempted, on the premise that a synthetically derived artificial antigen might be capable of modulating the immune response in mice to produce elevated levels of cross-reactive group B meningococcal polysaccharide-specific antibodies. To achieve this, the antigenicity of the modified polysaccharide to group B meningococcal polysaccharide-specific antibodies had to be preserved, and this criterion could only be satisfied in modifications in which the carboxylate and N-carbonyl groups of the sialic acid residues of polysaccharide remained intact. Therefore, the most successful modifications were accomplished by N-deacetylation of the group B meningococcal polysaccharide with strong base to yield a precursor that could then be N-acetylated or N-arylated with different substituents. For example, the introduction of N-propionyl groups, followed by conjugation of the resultant N-propionylated group B meningococcal polysaccharide to tetanus toxoid, yielded an antigen that when injected in mice induced in them high levels of cross-reactive group B meningococcal polysaccharide-specific IgG antibodies. The T cell dependency of this antigen was established when it was demonstrated that the levels of these B polysaccharide-specific antibodies could be significantly boosted by using both the N-propionylated- and native N-acetylated-group B meningococcal polysaccharide-tetanus toxoid conjugates.

Animals↗

PubMed1999

[A new vaccine concept: polysaccharide conjugate vaccines].

Polysaccharide-based vaccines such as the vaccines against Neisseiria meningitidis group A and C or Streptococcus pneumoniae have proved their efficacy in children and adults. Nevertheless they induce B cell mediated immunological response and therefore fail to protect infants. In the eighties appeared a new concept of Polysaccharide based vaccine for infants: Polysaccharide conjugate vaccines. Coupling polysaccharide to carrier protein transforms the T-independent antigen into T-dependant antigen. The first conjugate vaccines for the prevention of infections caused by Haemophilus influenzae type b were a success, with a 95% efficacy. A worldwide vaccination program might lead to the eradication of that bacterial disease. New vaccines are currently under development, the next conjugate vaccine should be one against Streptococcus pneumoniae. First published clinical data are very promising and confirmed the potential of the polysaccharide conjugate vaccine approach against bacterial infections.

Animals↗

PubMed2002

Safety, reactogenicity, and immunogenicity of a tetravalent meningococcal polysaccharide-diphtheria toxoid conjugate vaccine given to healthy adults.

Healthy adults, 18-55 years old, were immunized once with a tetravalent (serogroups A, C, Y, and W-135) meningococcal vaccine conjugated to diphtheria toxoid at 1 of 3 doses and were monitored for safety, reactogenicity, and immunogenicity. No immediate reactions were observed. Only 1 of 89 subjects reported fever; only 1 reported any severe reactogenicity (local pain/soreness, chills, arthralgia, anorexia, and malaise). For each serogroup and in each dose group, the geometric mean serum bactericidal antibody (SBA) titer and immunoglobulin G concentration increased after immunization. In the 4- and 10-microg-dose groups, all subjects had SBA titers >/=8 against serogroups A and C, and 89% and 93% of subjects had SBA titers >/=8 against serogroups Y and W-135, respectively. The A, C, Y, and W-135 Neisseria meningitidis-diphtheria toxoid conjugate vaccine, when given to healthy adults as a single intramuscular injection of 1, 4, or 10 microg/serogroup, is acceptably tolerated and immunogenic and deserves further development.

Adult↗

PubMed2002

Standard and alternative regimens of Haemophilus influenzae type b conjugate vaccine (polyribosylribitol phosphate-tetanus toxoid conjugate vaccine) elicit comparable antibody avidities in infants.

BACKGROUND: Haemophilus influenzae type b conjugate vaccines are relatively expensive in the developing world. Previous study of the type b conjugate vaccine polyribosylribitol phosphate-tetanus toxoid conjugate vaccine showed that two dose and fractional three dose schedules elicit protective antibody concentrations equivalent to three full doses. METHODS: Antibody avidity was measured in 73 of these vaccinees with a modified enzyme-linked immunosorbent assay using NH(4) SCN as the chaotrope. Avidity index (AI) is the molarity causing a 50% reduction in OD(405). RESULTS: The postprimary series AI was similar for all dosing regimens. Preboost AI was highest in those receiving three half-doses, although there was no statistical difference among groups. Rises in avidity from age 8 to 12 months were also similar among regimens. Our data support the equivalence of anti-polyribosylribitol phosphate IgG avidity in infants primed with these alternative regimens. CONCLUSIONS: Given the known correlation of avidity with assays of bacterial killing and memory priming, these potentially more economical alternative schedules should be studied in the developing world.

Antibodies, Bacterial↗

PubMed1990

Immunogenicity of Haemophilus b conjugate vaccine (meningococcal protein conjugate) in children with prior invasive Haemophilus influenzae type b disease.

Children younger than 2 years of age with previous invasive Haemophilus influenzae (Hib) type b disease may not develop protective antibodies to antigens of Hib and may be at risk of developing a second episode of Hib disease. Twenty-three children with prior Hib disease were immunized with Haemophilus b conjugate vaccine (meningococcal protein conjugate). Children 12 to 24 months of age were given one dose of vaccine and children younger than 12 months of age were given 2 doses 2 months apart. Antibody to the polysaccharide capsule of Hib (PRP) was measured by radioimmunoassay. Eighteen children had preimmunization serum antibody concentrations less than 0.150 micrograms/ml. All 18 children responded with greater than 0.150 micrograms/ml of antibody after a single dose of vaccine. Only 1 of the 23 children had a preimmunization serum antibody concentration greater than 1.000 micrograms/ml. Seventeen children ultimately responded with greater than 1.000 micrograms/ml of antibody (P less than 0.0001), concentrations of antibody thought to correlate with protection. Haemophilus b conjugate vaccine (meningococcal protein conjugate) is immunogenic in children with invasive Hib disease. Children younger than 2 years of age with invasive Hib disease should be subsequently immunized with a Hib conjugate vaccine.

Age Factors↗