Pneumococcal conjugate and plain polysaccharide vaccines have divergent effects on antigen-specific B cells.

BACKGROUND: A 23-valent unconjugated pneumococcal polysaccharide vaccine (23vP), routinely administered at the age of 65, has limited effectiveness, and revaccination induces attenuated antibody responses. It is not known whether pneumococcal polysaccharide-protein conjugated vaccines (PCV), although highly effective in infants, offer any immunological advantages over 23vP in adults. METHODS: We immunized adults with schedules combining both PCV and 23vP and investigated B-cell responses to establish whether PCV7 (a 7-valent PCV) induced T-dependent responses in adults, to assess the role of memory B cells in 23vP-induced antibody hyporesponsiveness, and to identify the B-cell subtypes involved. RESULTS: A single dose of PCV7 induced significant increases in serotype-specific memory B-cell populations in peripheral blood indicating a T-dependent response. Conversely, immunization with 23vP resulted in a decrease in memory B-cell frequency. Furthermore, memory B-cell responses to subsequent immunization with PCV7, when given after 23vP, were attenuated. Notably, B1b cells, a subset important in protecting mice against pneumococci, were also depleted following immunization with 23vP in humans. CONCLUSIONS: This study indicates that PCV7 may have an immunological advantage over 23vP in adults and that 23vP-induced depletion of memory and B1b-cell subsets may provide a basis for antibody hyporesponsiveness and the limited effectiveness of 23vP. Clinical Trials Registration. ISRCTN: 78768849.

Persistence of serum bactericidal antibody one year after a booster dose of either a glycoconjugate or a plain polysaccharide vaccine against serogroup C Neisseria meningitidis given to adolescents previously immunized with a glycoconjugate vaccine.

BACKGROUND: Bactericidal antibody induced by immunization of infants with serogroup C Neisseria meningitidis (MenC) vaccines wanes rapidly during childhood. Adolescents are at particular risk from meningococcal disease, therefore they might benefit from a booster dose of vaccine. The duration of serologic response to such a booster in adolescents is unknown. METHODS: In a previous study, English schoolchildren, aged 9 to 12 years, who had received a monovalent MenC glycoconjugate vaccine in 1999-2000, were given either a plain polysaccharide vaccine (MenC-PS group, n = 150) or a glycoconjugate vaccine (MenC-CRM group, n = 95) at 13 to 15 years of age. In this follow-up study, serum bactericidal antibody titers and specific immunoglobulin G concentrations were assessed 1 year later. Results were compared with unboosted controls of similar age (control group, n = 298). RESULTS: Compliance with study protocol was achieved for 146 of the MenC-PS group, 92 of the MenC-CRM group, and 293 of the control group. Compared with the control group, both the MenC-PS and MenC-CRM groups had a significantly higher (P < 0.0001) geometric mean serum bactericidal antibody titers 1 year after the booster dose (geometric mean titers for MenC-PS group 3388 [95% confidence interval {CI}: 2460-4665]; MenC-CRM group 4417 [95% CI: 2951-6609]; control group 316 [95% CI: 252-396]). Specific immunoglobulin G concentration also rose and remained elevated 1 year after the booster. CONCLUSIONS: A booster dose of MenC vaccine given to adolescents produced a marked rise in bactericidal antibody, which remained elevated 1 year later. Introduction of an adolescent booster of MenC vaccine might provide enhanced long-term population control of the disease.

A randomized study comparing combined pneumococcal conjugate and polysaccharide vaccination schedules in adults.

BACKGROUND: The widely used 23-valent plain polysaccharide vaccine (23vP) has limited effectiveness, produces short-lived immune responses, and induces attenuated antibody production after subsequent challenge with pneumococcal vaccines. Our goal was to examine whether priming with the 7-valent pneumococcal conjugate vaccine (PCV7) could enhance the immunogenicity of 23vP for the PCV7 serotypes and to investigate whether 23vP induced hyporesponsiveness could be overcome using PCV7. METHODS: We conducted an open-label randomized study that compared 3 vaccine schedules, each of which consisted of 2 doses of PCV7 and 1 dose of 23vP (23vP-PCV7-PCV7, PCV7-23vP-PCV7, PCV7-PCV7-23vP) administered over a 1-year period in a cohort of 348 adults 50-70 years of age. All vaccines were administered intramuscularly and were given 6 months apart. Blood samples were obtained prior to and 1 month after each vaccination. RESULTS: 23vP administered after priming with 2 doses of PCV7 produced significantly higher antibody concentrations for 3 of the 7 PCV7 serotypes, compared with vaccination with a single dose of 23vP; however, the same immunogenicity could be achieved with a single dose of PCV7. Prior vaccination with 23vP attenuated the antibody response to subsequent PCV7, which was not restored by additional doses of PCV7. CONCLUSION: In adults, vaccination schedules combining PCV7 and 23vP do not provide improved immunogenicity over the use of a single dose of 23vP for most of the serotypes contained in PCV7.

A simplified 4-site economical intradermal post-exposure rabies vaccine regimen: a randomised controlled comparison with standard methods.

BACKGROUND: The need for economical rabies post-exposure prophylaxis (PEP) is increasing in developing countries. Implementation of the two currently approved economical intradermal (ID) vaccine regimens is restricted due to confusion over different vaccines, regimens and dosages, lack of confidence in intradermal technique, and pharmaceutical regulations. We therefore compared a simplified 4-site economical PEP regimen with standard methods. METHODS: Two hundred and fifty-four volunteers were randomly allocated to a single blind controlled trial. Each received purified vero cell rabies vaccine by one of four PEP regimens: the currently accepted 2-site ID; the 8-site regimen using 0.05 ml per ID site; a new 4-site ID regimen (on day 0, approximately 0.1 ml at 4 ID sites, using the whole 0.5 ml ampoule of vaccine; on day 7, 0.1 ml ID at 2 sites and at one site on days 28 and 90); or the standard 5-dose intramuscular regimen. All ID regimens required the same total amount of vaccine, 60% less than the intramuscular method. Neutralising antibody responses were measured five times over a year in 229 people, for whom complete data were available. FINDINGS: All ID regimens showed similar immunogenicity. The intramuscular regimen gave the lowest geometric mean antibody titres. Using the rapid fluorescent focus inhibition test, some sera had unexpectedly high antibody levels that were not attributable to previous vaccination. The results were confirmed using the fluorescent antibody virus neutralisation method. CONCLUSIONS: This 4-site PEP regimen proved as immunogenic as current regimens, and has the advantages of requiring fewer clinic visits, being more practicable, and having a wider margin of safety, especially in inexperienced hands, than the 2-site regimen. It is more convenient than the 8-site method, and can be used economically with vaccines formulated in 1.0 or 0.5 ml ampoules. The 4-site regimen now meets all requirements of immunogenicity for PEP and can be introduced without further studies. TRIAL REGISTRATION: Controlled-Trials.com ISRCTN 30087513.

Rotavirus diarrhoea and future prospects for prevention.

Rotavirus is a highly contagious cause of vomiting and diarrhoea in young children (Glass et al, 2006). It is transmitted via the faecal-oral route and almost every child will experience an episode of rotavirus infection before the age of five years. Although this infection leads to millions of deaths per year in developing countries, good access to dehydration therapies in the UK means that we experience few rotavirus deaths. Nevertheless, rotavirus infection can cause misery for the child and presents indirect costs for parents. It also poses a substantial burden on primary care and paediatric wards, particularly during the busy winter period, with nosocomial infection adding, on average, a further four days to a child's stay in hospital. With no antiviral treatment available, management of the poorly child must focus on prevention of dehydration. Recently, two new generation rotavirus vaccines have been licensed with each undergoing extensive and large clinical trials. These vaccines offer new hope for the prevention of this condition.

A randomized study comparing the safety and immunogenicity of a conjugate vaccine combination containing meningococcal group C and pneumococcal capsular polysaccharide--CRM197 with a meningococcal group C conjugate vaccine in healthy infants: challenge phase.

BACKGROUND: A combination nonavalent pneumococcal-group C meningococcal conjugate vaccine (Pnc9-MenC) was previously found to be safe and immunogenic when administered to infants at 2, 3 and 4 months. This study describes the persistence of immunity at 12 months of age and the immunologic response to a challenge dose of either meningococcal polysaccharide vaccine (Meningivac A+C; MnA+C), or MenC. METHODS: A phase II, randomized, controlled trial of healthy infants. Subjects were given Pnc9-MenC or MenC vaccine at 2, 3 and 4 months of age and then challenged with either MenC or MnA+C. Group C meningococcal immunogenicity was measured by serum bactericidal assay (SBA) and an enzyme-linked immunosorbent assay (ELISA) adapted to measure antibody avidity pre- and post-challenge. RESULTS: The MenC vaccine was more immunogenic than the Pnc9-MenC vaccine in persistence of serogroup C meningococcal polysaccharide antibodies at 12 months of age. Post-challenge at 13 months there were significant differences between the four groups in the induction of serogroup C meningococcal polysaccharide antibodies. The responses to MenC/MenC were significantly higher than in the other groups (p<0.001) and the responses to Pnc9-MenC/MnA+C were significantly lower than in the other groups (p<0.001). There was no difference between the four groups in the proportions with geometric mean concentrations (GMC) greater than 2 microg/ml (p=0.18) or with SBA titres greater than or equal to the protective level of 1:8 (p=0.89). The SBA geometric mean ratio (GMR) between pre- and post-challenge was higher in the groups challenged with MenC than those challenged with MnA+C. Antibody avidity increased over time. CONCLUSION: We have shown that Pnc9-MenC primes effectively for immunological memory. At 13 months of age the highest immune responses were seen in the subjects primed and challenged with MenC alone. However, all groups achieved the threshold levels required for protection.

Serogroup C meningococcal glycoconjugate vaccine in adolescents: persistence of bactericidal antibodies and kinetics of the immune response to a booster vaccine more than 3 years after immunization.

BACKGROUND: The persistence of protection from meningococcal disease following immunization with serogroup C meningococcal (MenC) glycoconjugate vaccines in infancy is short-lived. The duration of protective immunity afforded by these vaccines in other at-risk age groups (i.e., adolescents and young adults) is not known. We evaluated the persistence of bactericidal antibodies following immunization with a MenC glycoconjugate vaccine (MenCV) in adolescents and the kinetics of immune response to a meningococcal AC plain polysaccharide vaccine (MenPS) challenge or a repeat dose of MenCV. METHODS: We conducted a randomized comparative trial of 274 healthy 13-15-year-olds from whom a total of 4 blood samples were obtained (prior to administration of a dose of MenPS or MenCV, again on 2 further occasions at varying times from days 2-7 after vaccination, and finally on day 28 after vaccination. The correlate of protection was a serum bactericidal assay titer > or = 8 (with a serum bactericidal assay using human complement). RESULTS: A serum bactericidal assay using human complement titer > or = 8 was observed in 75% of participants at baseline (mean age, 14.5 years; mean time since routine MenCV vaccination, 3.7 years). No increase in serum bactericidal assay geometric mean titers was detected until day 5 after administration of MenPS. Geometric mean titers following administration of MenCV were significantly higher than those observed following administration of MenPS, at days 5, 7, and 28. CONCLUSIONS: This study showed sustained levels of bactericidal antibodies for at least 3 years after immunization of adolescents with MenCV. After challenge of immunized adolescents with MenPS, there was no increase in serum bactericidal assay observed until day 5 after vaccination, indicating that immunological memory may be too slow to generate protection against this potentially rapidly invasive organism.

Capsular serotype-specific attack rates and duration of carriage of Streptococcus pneumoniae in a population of children.

BACKGROUND: The relative invasiveness rates (attack rates) of Streptococcus pneumoniae of different capsular serotypes in children are not known. Estimates of capsular serotype invasiveness (designated "invasive odds ratios") that are based on cross-sectional prevalence carriage data have been published, but these estimates could be biased by variation in the duration of carriage. METHODS: The relative attack rates of invasive pneumococci were measured using national UK surveillance data on invasive pneumococcal disease (IPD) incidence and data on incidence of pneumococcal acquisition from longitudinal studies of nasopharyngeal pneumococcal carriage. RESULTS: We found significant differences in capsular serotype-specific attack rates. For example, capsular serotypes 4, 14, 7F, 9V, and 18C were associated with rates of >20 IPD cases/100,000 acquisitions, whereas capsular serotypes 23F, 6A, 19F, 16F, 6B, and 15B/C were associated with <10 IPD cases/100,000 acquisitions. There was an inverse relationship between duration of carriage and attack rate by capsular serotype (P<.0001). Attack rates were significantly correlated with invasive odds ratios (P<.0001). CONCLUSIONS: The capsular serotype is a major determinant of both pneumococcal duration of carriage and attack rate. Published invasive odds ratios are a reliable and practical method of determining capsular serotype invasiveness and will be valuable for investigating and characterizing emerging capsular serotypes in the context of conjugate vaccination.

Parental views on the introduction of an infant pneumococcal vaccine.

Streptococcus pneumoniae is a major cause of early childhood morbidity and mortality. A heptavalent pneumococcal conjugate vaccine (PnC7) is licensed for use and could prevent the majority of infant invasive pneumococcal infections. A recent announcement confirmed its inclusion into the U.K. childhood immunisation programme. In anticipation of PnC7 being recommended for use, this study explored parental understanding of pneumococcal disease and their views on the possible introduction of this vaccine. Twenty three interviews and two focus groups were held with parents of children under two years of age. Four main themes emerged from the data analysis: 'Confidence and belief in immunisation'; 'Anxiety about immunisation'; 'Trust and understanding of immunisation information' and 'Response to a new immunisation'. Overall parental confidence in immunisation has been affected by the MMR controversy. With little knowledge of pneumococcal disease, parents want information about the safety and effectiveness of PnC7. Information needs to be conveyed in a way that restores parents' trust in immunisation.

Childhood immunisation (1): planned changes to the routine schedule.

With significant changes planned for the childhood immunisation schedule, this two-part series looks at the recommendations and their rationale in order to help community practitioners explain the revisions to parents. This article discusses the introduction of a pneumococcal vaccine and catch-up programme to the schedule. In the next article, other changes to the schedule will be examined along with the process of reassuring parents

Effect of needle size on immunogenicity and reactogenicity of vaccines in infants: randomised controlled trial.

OBJECTIVES: To assess the immunogenicity of vaccines for infants and to investigate whether the incidence of reactogenicity is reduced after each immunisation dose using needles of varying lengths and gauges. DESIGN: Randomised controlled trial. SETTING: 18 general practices within two UK primary care trusts. PARTICIPANTS: 696 healthy infants vaccinated at 2, 3, and 4 months of age, with follow-up to 5 months of age. INTERVENTIONS: Combined diphtheria, tetanus, whole cell pertussis, and Haemophilus influenzae type b vaccine and a serogroup C meningococcal glycoconjugate vaccine administered using either a wide, long needle (23 gauge/0.6 mm diameter, 25 mm), a narrow, short needle (25 gauge/0.5 mm diameter, 16 mm), or a narrow, long needle (25 gauge, 25 mm). MAIN OUTCOME MEASURES: Local and general reactions recorded by parents for three days after each dose; and diphtheria, tetanus, and H influenzae type b antibody concentrations and functional antibody against serogroup C Neisseria meningitidis 28-42 days after the third dose. RESULTS: Local reactions to diphtheria, tetanus, whole cell pertussis, H influenzae type b vaccinations decreased significantly with wide, long needles compared with narrow, short needles. At all three doses one less infant experienced local reactions at days 1, 2, or 3 for every six to eight vaccinated. Significantly fewer infants vaccinated with the long needle experienced severe local reactions. Non-inferiority of the immune response was shown using a wide, long needle rather than a narrow, short needle for serogroup C meningococcal glycoconjugate vaccine and for diphtheria but not for H influenzae type b or tetanus, although no evidence was found of a decrease. Little difference was found between needles of the same length but different gauges in local reaction or immune response. CONCLUSIONS: Long (25 mm) needles for infant immunisations can significantly reduce vaccine reactogenicity at each dose while achieving comparable immunogenicity to that of short (16 mm) needles. Trial registration Current Controlled Trials ISRCTN62032215 [controlled-trials.com].

Childhood immunisation: planned changes to the routine schedule (2).

With significant changes planned for the childhood immunisation schedule, this two-part series looks at the recommendations and their rationale in order for community practitioners to help explain the changes to parents. In the last issue, the introduction of a pneumococcal vaccine to the schedule was discussed. This article focuses on the re-spacing of the meningococcal vaccination and other changes to the schedule, and describes methods for reassuring parents.

CRM197-conjugated serogroup C meningococcal capsular polysaccharide, but not the native polysaccharide, induces persistent antigen-specific memory B cells.

Neisseria meningitidis is one of the leading causes of bacterial meningitis and septicemia in children. Vaccines containing the purified polysaccharide capsule from the organism, a T cell-independent antigen, have been available for decades but do not appear to provide protection in infancy or immunologic memory as measured by antibody responses. By contrast, T cell-dependent serogroup C protein-polysaccharide conjugate vaccines protect against serogroup C meningococcal disease from infancy onward and prime for immunologic memory. We compared the magnitude and kinetics of plasma cell and memory B-cell responses to a meningococcal plain polysaccharide vaccine and a serogroup C glycoconjugate vaccine in adolescents previously primed with the conjugate vaccine. Plasma cell kinetics were similar for both vaccines, though the magnitude of the response was greater for the glycoconjugate. In contrast to the glycoconjugate vaccine, the plain polysaccharide vaccine did not induce a persistent immunoglobulin G (IgG) memory B-cell response. This is the first study to directly show that serogroup C meningococcal glycoconjugate vaccines induce persistent production of memory B cells and that plain polysaccharide vaccines do not, supporting the use of the conjugate vaccine for sustained population protection. Detection of peripheral blood memory B-cell responses after vaccination may be a useful signature of successful induction of immunologic memory during novel vaccine evaluation.

Understanding and dealing with parental vaccine concerns.

Parents often worry more about vaccines than the diseases they prevent. This article highlights the issues that commonly concern parents and suggests appropriate information that nurses can give to reassure them and promote vaccination.

Immunogenicity and immunologic memory of meningococcal C conjugate vaccine in premature infants.

BACKGROUND: Protein-polysaccharide conjugate vaccines against Neisseria meningitidis serogroup C were introduced into the U.K. routine immunization schedule in 1999. This study is the first to describe both persistence of antibody and evidence for induction of immune memory using meningococcal C conjugate (MCC) vaccine in preterm infants. METHODS: Immunogenicity and induction of immunologic memory by as MCC vaccine was assessed in premature infants; 62 preterm and 60 term controls received MCC at the accelerated schedule (2, 3 and 4 months of age). A meningococcal C polysaccharide challenge was administered at 12 months of age. RESULTS: Both groups achieved similar protective titers after primary immunization that then waned significantly by 1 year of age. Postchallenge serum bactericidal activity was significantly lower in preterm infants (P = 0.03); 73% of preterm versus 88% of term controls achieved a 4-fold rise in serum bactericidal activity (P = 0.07). CONCLUSIONS: MCC vaccine is immunogenic and primes for immunologic memory in preterm infants. The decreased memory responses in these preterm infants in conjunction with waning clinical efficacy data for all U.K. infants suggest a role for a routine booster dose of vaccine in all infants receiving MCC, especially those born preterm.

Immunogenicity and safety of a combination pneumococcal-meningococcal vaccine in infants: a randomized controlled trial.

CONTEXT: The success of conjugate vaccines in decreasing invasive disease due to Streptococcus pneumoniae and group C Neisseria meningitidis has placed pressure on crowded infant immunization schedules, making development of combination vaccines a priority. OBJECTIVE: To determine the safety and immunogenicity of a combination 9-valent pneumococcal-group C meningococcal conjugate candidate vaccine (Pnc9-MenC) administered as part of the routine UK infant immunization schedule at ages 2, 3, and 4 months. DESIGN, SETTING, AND PARTICIPANTS: Phase 2 randomized controlled trial conducted from August 2000 to January 2002 and enrolling 240 healthy infants aged 7 to 11 weeks from 2 UK centers, with home follow-up visits at ages 2, 3, 4, and 5 months. INTERVENTION: Pnc9-MenC (n = 120) or monovalent group C meningococcal conjugate vaccine (MenC) (n = 120) administered in addition to routine immunizations (diphtheria and tetanus toxoids and whole-cell pertussis [DTwP], Haemophilus influenzae type b [Hib] polyribosylribitol phosphate-tetanus toxoid protein conjugate, oral polio vaccine). MAIN OUTCOME MEASURES: Group C meningococcal immunogenicity measured by serum bactericidal titer (SBT) 1 month following the third dose; rates of postimmunization reactions. RESULTS: MenC component immunogenicity was reduced in the Pnc9-MenC vs the MenC group (geometric mean SBT, 179 [95% confidence interval {CI}, 133-243] vs 808 [95% CI, 630-1037], respectively; P<.001). The proportion with group C meningococcal SBT greater than 1:8 was lower in the Pnc9-MenC vs the MenC group (95% vs 100%, P = .05). The geometric mean concentration of antibodies to concomitantly administered Hib vaccine was reduced in the Pnc9-MenC vs the MenC group (2.11 [95% CI, 1.57-2.84] microg/mL vs 3.36 [95% CI, 2.57-4.39] microg/mL; P = .02), as were antibodies against diphtheria (0.74 [95% CI, 0.63-0.87] microg/mL vs 1.47 [95% CI, 1.28-1.69] microg/mL; P<.001). Pnc9-MenC was immunogenic for each of 9 contained pneumococcal serotypes, with responses greater than 0.35 microg/mL observed in more than 88% of infants. Increased irritability and decreased activity were observed after the third dose in the Pnc9-MenC group. CONCLUSIONS: Pnc9-MenC combination vaccine administered to infants at ages 2, 3, and 4 months demonstrated reduced group C meningococcal immunogenicity compared with MenC vaccine. The immunogenicity of concomitantly administered Hib and DTwP vaccines was also diminished. The Pnc9-MenC vaccine was safe and immunogenic for all contained pneumococcal serotypes. The reduced MenC immunogenicity may limit the development of the Pnc9-MenC vaccine.