Sampling methods for the study of pneumococcal carriage: A systematic review

Streptococcus pneumoniae is an important pathogen worldwide. Accurate sampling of S. pneumoniae carriage is central to surveillance studies before and following conjugate vaccination programmes to combat pneumococcal disease. Any bias introduced during sampling will affect downstream recovery and typing. Many variables exist for the method of collection and initial processing, which can make inter-laboratory or international comparisons of data complex. In February 2003, a World Health Organisation working group published a standard method for the detection of pneumococcal carriage for vaccine trials to reduce or eliminate variability. We sought to describe the variables associated with the sampling of S. pneumoniae from collection to storage in the context of the methods recommended by the WHO and those used in pneumococcal carriage studies since its publication. A search of published literature in the online PubMed database was performed on the 1st June 2012, to identify published studies that collected pneumococcal carriage isolates, conducted after the publication of the WHO standard method. After undertaking a systematic analysis of the literature, we show that a number of differences in pneumococcal sampling protocol continue to exist between studies since the WHO publication. The majority of studies sample from the nasopharynx, but the choice of swab and swab transport media is more variable between studies. At present there is insufficient experimental data that supports the optimal sensitivity of any standard method. This may have contributed to incomplete adoption of the primary stages of the WHO detection protocol, alongside pragmatic or logistical issues associated with study design. Consequently studies may not provide a true estimate of pneumococcal carriage. Optimal sampling of carriage could lead to improvements in downstream analysis and the evaluation of pneumococcal vaccine impact and extrapolation to pneumococcal disease control therefore further in depth comparisons would be of value.     

Immunologic non-inferiority and safety of the investigational pneumococcal non-typeable Haemophilus influenzae protein D-conjugate vaccine (PHiD-CV) 4-dose vial presentation compared to the licensed PHiD-CV 1-dose vial presentation in infants: A phase III randomized study

BackgroundTo support vaccination programs in developing countries, a 4-dose vial presentation of pneumococcal non-typeable Haemophilus influenzae protein D-conjugate vaccine (PHiD-CV) was developed. This study assessed immunologic non-inferiority and safety of the investigational PHiD-CV 4-dose versus licensed 1-dose vial presentation in infants.MethodsIn this phase III, mono-center, observer-blind study in Bangladesh, 6–10-week-old infants were randomized 1:1 to receive PHiD-CV primary vaccination (at ages 6, 10, 18 weeks) and a booster dose (at age 9 months) with a 4-dose vial (with preservative, 4DV group) or 1-dose vial (preservative-free, 1DV group). DTPw-HBV/Hib was (co)-administered per study protocol and polio, measles and rubella vaccines as part of the national immunization program. Non-inferiority of PHiD-CV 4-dose versus 1-dose vial for each vaccine pneumococcal serotype (VT) and vaccine-related serotype 19A in terms of antibody geometric mean concentration (GMC) was assessed (criterion: upper limit of 2-sided 95% confidence interval of antibody GMC ratios [1DV/4DV] <2-fold). Immune responses were measured. Solicited, unsolicited and serious adverse events (AEs) were evaluated.ResultsOf 320 infants (160 per group) vaccinated during the primary vaccination phase, 297 received a booster. Non-inferiority was demonstrated for each VT and 19A. One month post-primary vaccination, for most VT, ≥97.9% of infants in each group had antibody concentrations ≥0.2 μg/mL; for 19A ≥ 80.1% reached this threshold. Pneumococcal antibody responses and opsonophagocytic activity for each VT and 19A were within similar ranges between groups after primary and booster vaccination, as were anti-protein D responses. Booster immune responses were observed in both groups. Reported AEs were within similar ranges for both presentations.ConclusionImmunologic non-inferiority of PHiD-CV 4-dose vial (with preservative) versus PHiD-CV 1-dose vial (preservative-free) was demonstrated. Immune responses and reactogenicity following primary/booster vaccination were within similar ranges for both presentations. PHiD-CV 4-dose vial would help improve access and coverage in resource-limited countries.Clinical Trial Registry: NCT02447432.     

Pneumococcal conjugated vaccine: PHiD-CV

At the beginning of a new century, we have gained significant achievements against pneumococcal infections by using conjugated pneumococcal vaccines. In January 2009, the EMEA issued a positive opinion about, and recommended the approval of, GlaxoSmithKline’s pediatric pneumococcal candidate vaccine, which is indicated for active immunization against invasive pneumococcal disease (IPD) and acute otitis media caused by Streptococcus pneumoniae in infants and children from 6 weeks up to 2 years of age. The approved 10-valent pneumococcal vaccine (PHiD-CV) contains all serotypes in 7-valent pneumococcal conjugate vaccine (PCV-7) plus serotypes 1, 5 and 7F. Protein D from nontypeable Haemophilus influenzae is the carrier protein for eight serotypes, while tetanus and diphtheria toxins are in the carrier proteins for the remaining two serotypes. It has also been proved that PHiD-CV is immunogenic, safe and well-tolerated in children. This vaccine can be coadministered with routinely used pediatric vaccines. Noninferiority criteria of PHiD-CV compared with PCV-7 were established in shared serotypes, except for serotypes 6B and 23F, and PHiD-CV is immunogenic for additional serotypes as assessed by the percentage of subjects with antibody concentrations. PHiD-CV is also immunogenic for ten serotypes as assessed by post-primary and post-booster dose opsonophagocytic activity responses. Vaccine efficacy against IPD and other conditions should be monitored for shared serotypes and also additional serotypes during the postmarketing period. Optimal scheduling, safety and immunogenicity data in children with different risk factors for IPD, or whether it will provide herd immunity, are the questions waiting for answers in the postmarketing period. Further studies are needed to assess the potential advantages of protein D as a carrier and the potential efficacy of this new vaccine against H. influenzae. The potential public health efficacy of PHiD-CV in low-income countries, where IPD and pneumonia are a major public health problem, is a major concern.     

Comparison between a new multiplex electrochemiluminescence assay and the WHO reference enzyme-linked immunosorbent assay to measure serum antibodies against pneumococcal serotype-specific polysaccharides

Background

Two electrochemiluminescence (ECL) assays were developed which, together, can simultaneously measure serum antibodies against pneumococcal capsular polysaccharides (PnPS) for 17 serotypes. The assays were validated for the 13 PnPS included in the 13-valent pneumococcal conjugate vaccine (PCV13). As recommended by the World Health Organization (WHO), we compared the ECL assays with the WHO reference enzyme-linked immunosorbent assay (ELISA) and derived a threshold corresponding to the 0.35?µg/mL threshold established for the WHO reference ELISA for the non-inferiority comparison and licensure of new PCVs against invasive pneumococcal disease.

Immunogenicity,safety and reactogenicity of the pneumococcal non-typeable Haemophilus influenzae protein D conjugate vaccine (PHiD-CV) in 2–17-year-old children with asplenia or splenic dysfunction: A phase 3 study

BackgroundImmunization with pneumococcal vaccines is an important prophylactic strategy for children with asplenia or splenic dysfunction, who are at high risk of bacterial infections (including S. pneumoniae). This study aimed to assess immunogenicity and safety of pneumococcal non-typeable Haemophilus influenzae protein D conjugate vaccine (PHiD-CV, GSK) in this at-risk population.MethodsThis phase III, multi-centre, open-label, controlled study, in which at-risk children with asplenia or splenic dysfunction were enrolled (age strata: 2–4, 5–10 and 11–17 years), was conducted in Poland and the Russian Federation. For the 2–4 years at-risk group, healthy age-matched children were enrolled as control. Unprimed children (not previously vaccinated with any pneumococcal vaccine) received 2 PHiD-CV doses (≥2 months apart) and pneumococcal vaccine-primed children received 1 dose. Immune responses were assessed pre-vaccination and one month post-each dose. Solicited and unsolicited adverse events (AEs) were recorded for 4 and 31 days post-vaccination, respectively, and serious AEs (SAEs) throughout the study.ResultsOf 52 vaccinated children (18 at-risk primed, 28 at-risk unprimed and 6 control unprimed), 45 (18, 23 and 4, respectively) were included in the according-to-protocol cohort for immunogenicity. Post-vaccination (post-dose 1 in primed and post-dose 2 in unprimed children), for each vaccine pneumococcal serotype and vaccine-related serotype 6A all at-risk children had antibody concentrations ≥0.2 µg/mL, and for vaccine-related serotype 19A at least 94.4%. Increases in antibody geometric mean concentrations were observed. For most serotypes, all at-risk children had post-vaccination opsonophagocytic activity (OPA) titers ≥8 and increases in OPA geometric mean titers were observed. No safety concerns were raised. One non-fatal SAE (respiratory tract infection, considered not vaccine-related) was reported by one at-risk unprimed child.ConclusionPHiD-CV was immunogenic and well tolerated in 2–17-year-old children with asplenia or splenic dysfunction.Clinical Trial Registry: www.clinicaltrials.gov, NCT01746108.     

Immunogenicity and safety of 11- and 12-valent pneumococcal non-typeable Haemophilus influenzae protein D-conjugate vaccines (11vPHiD-CV, 12vPHiD-CV) in infants: Results from a phase II,randomised, multicentre study

Background

We assessed 2 investigational 11- and 12-valent vaccines, containing capsular polysaccharides of 10 serotypes as in the pneumococcal non-typeable Haemophilus influenzae protein D-conjugate vaccine (PHiD-CV) and CRM₁₉₇-conjugated capsular polysaccharides of serotypes 19A (11-valent) or 19A and 6A (12-valent).

Economic evaluation of second generation pneumococcal conjugate vaccines in Norway

Background

A seven valent pneumococcal conjugate vaccine (PCV7) was introduced in the Norwegian childhood immunization programme in 2006, and since then the incidence of invasive pneumococcal disease has declined substantially. Recently, two new second generation pneumococcal conjugate vaccines have become available, and an update of the economic evidence is needed. The aim of this study was to estimate incremental costs, health effects and cost-effectiveness of the pneumococcal conjugate vaccines PCV7, PCV13 and PHiD-CV in Norway.

Methods

We used a Markov model to estimate costs and epidemiological burden of pneumococcal- and NTHi-related diseases (invasive pneumococcal disease (IPD), Community Acquired Pneumonia (CAP) and acute otitis media (AOM)) for a specific birth cohort. Using the most relevant evidence and assumptions for a Norwegian setting, we calculated incremental costs, health effects and cost-effectiveness for different vaccination strategies. In addition we performed sensitivity analyses for key parameters, tested key assumptions in scenario analyses and explored overall model uncertainty using probabilistic sensitivity analysis.

Results

The model predicts that both PCV13 and PHiD-CV provide more health gains at a lower cost than PCV7. Differences in health gains between the two second generation vaccines are small for invasive pneumococcal disease but larger for acute otitis media and myringotomy procedures. Consequently, PHiD-CV saves more disease treatment costs and indirect costs than PCV13.

Conclusion

This study predicts that, compared to PVC13, PHiD-CV entails lower costs and greater benefits if the latter is measured in terms of quality adjusted life years. PVC13 entails more life years gained than PHiD-CV, but those come at a cost of NOK 3.1 million (∼€0.4 million) per life year. The results indicate that PHiD-CV is cost-effective compared to PCV13 in the Norwegian setting.     

Immunization of preterm infants with GSK’s hexavalent combined diphtheria-tetanus-acellular pertussis-hepatitis B-inactivated poliovirus-Haemophilus influenzae type b conjugate vaccine: A review of safety and immunogenicity

BackgroundInfants with history of prematurity (<37 weeks gestation) and low birth weight (LBW, <2500 g) are at high risk of infection due to functional immaturity of normal physical and immunological defense mechanisms. Despite current recommendations that infants with history of prematurity/LBW should receive routine immunization according to the same schedule and chronological age as full-term infants, immunization is often delayed.MethodsHere we summarize 10 clinical studies and 15 years of post-marketing safety surveillance of GSK’s hexavalent vaccine (DTPa-HBV-IPV/Hib), a combined diphtheria-tetanus-acellular-pertussis-hepatitis-B-inactivated-poliovirus-Haemophilus influenzae-type-b (Hib) conjugate vaccine, when administered alone, or co-administered with pneumococcal conjugate, rotavirus, and meningococcal vaccines and respiratory syncytial virus IgG to infants with history of prematurity/LBW in clinical trials.ResultsAt least 92.5% of infants with history of prematurity/LBW as young as 24 weeks gestation in clinical studies were seropositive to all vaccine antigens after 3-dose primary vaccination with GSK’s hexavalent DTPa-HBV-IPV/Hib vaccine, with robust immune responses to booster vaccination. Seropositivity rates and antibody concentrations to hepatitis B and Hib appeared lower in infants with history of prematurity/LBW than term infants. Between 13–30% of medically stable infants with history of prematurity developed apnea after vaccination with GSK’s hexavalent DTPa-HBV-IPV/Hib vaccine; usually after dose 1. The occurrence of post-immunization cardiorespiratory events appears to be influenced by the severity of any underlying neonatal condition. Most cardiorespiratory events resolve spontaneously or require minimal intervention. GSK’s hexavalent DTPa-HBV-IPV/Hib vaccine was well tolerated in co-administration regimens.ConclusionGSK’s hexavalent DTPa-HBV-IPV/Hib vaccine alone or co-administered with other pediatric vaccines has a clinically acceptable safety and immunogenicity profile when used in infants with history of prematurity/LBW for primary and booster vaccination. Additional studies are needed in very premature and very LBW infants. However, currently available data support using GSK’s hexavalent DTPa-HBV-IPV/Hib vaccine to immunize infants with history of prematurity/LBW according to chronological age.