Pneumococcal conjugated vaccine: PHiD-CV

Development of Next Generation Streptococcus pneumoniae Vaccines Conferring Broad Protection

Streptococcus pneumoniae is a major pathogen causing pneumonia with over 2 million deaths annually, especially in young children and the elderly. To date, at least 98 different pneumococcal capsular serotypes have been identified. Currently, the vaccines for prevention of S. pneumoniae infections are the 23-valent pneumococcal polysaccharide-based vaccine (PPV23) and the pneumococcal conjugate vaccines (PCV10 and PCV13). These vaccines only cover some pneumococcal serotypes and are unable to protect against non-vaccine serotypes and unencapsulated S. pneumoniae. This has led to a rapid increase in antibiotic-resistant non-vaccine serotypes. Hence, there is an urgent need to develop new, effective, and affordable pneumococcal vaccines, which could cover a wide range of serotypes. This review discusses the new approaches to develop effective vaccines with broad serotype coverage as well as recent development of promising pneumococcal vaccines in clinical trials. New vaccine candidates are the inactivated whole-cell vaccine strain (Δpep27ΔcomD mutant) constructed by mutations of specific genes and several protein-based S. pneumoniae vaccines using conserved pneumococcal antigens, such as lipoprotein and surface-exposed protein (PspA). Among the vaccines in Phase 3 clinical trials are the pneumococcal conjugate vaccines, PCV-15 (V114) and 20vPnC. The inactivated whole-cell and several protein-based vaccines are either in Phase 1 or 2 trials. Furthermore, the recent progress of nanoparticles that play important roles as delivery systems and adjuvants to improve the performance, as well as the immunogenicity of the nanovaccines, are reviewed.

Glycoconjugate vaccines: an update

INTRODUCTION

Globally, the three main pathogens causing serious infections are Haemophilus influenzae type b, Streptococcus pneumoniae and Neisseria meningitidis. Over the last 5 years, new vaccines protecting against these bacteria have been developed and introduced in various countries.

AREAS COVERED

This review describes the recently licensed glycoconjugates being used to protect against these encapsulated bacteria. Immunogenicity and safety data that led to licensure or licensure expansion of these glycoconjugates are discussed in addition to the resultant impact on the disease burden.

EXPERT OPINION

The maintenance of robust immunisation programmes with high uptake rates is important in maintaining low rates of disease. Epidemiological surveillance systems are essential in monitoring any changes in infectious disease trends and in identifying emerging infections such as from non-typeable H. influenzae, pneumococcal serotype replacement disease and changes in the epidemiology of meningococcal serogroups. This is important to guide future vaccine development. Accessibility of these glycoconjugate vaccines in resource poor regions, which bear the highest disease burden from these pathogens, remains challenging largely due to high vaccine pricing. Recent aids from public and private funding, tiered vaccine pricing and the transfer of vaccine technology have helped in introducing these vaccines where they are most needed.

Results of a national study on the awareness of and attitudes toward acute otitis media (AOM) among clinicians and the estimated direct healthcare costs in Turkey (TR-AOM Study)

AIMS

Acute otitis media (AOM) is one of the most frequent diagnoses and reasons for prescribing antibiotics in children. The aims of this prospective study were the following: (1) to assess the continuing education of physicians and the sources of information about AOM; (2) to assess the current knowledge of and attitudes toward AOM as well as the compliance with AOM guidelines; (3) to evaluate opinions about vaccines against AOM; and (4) to estimate the potential costs of AOM on the healthcare system in Turkey.

METHODS

This is a web-based cross-sectional survey of a national convenience sample of 600 physicians in Turkey (325 pediatricians (PEDs), 214 family physicians/general practitioners (FP&GPs) and 61 otolaryngologists (ENTs)).

RESULTS

Approximately 38.6% of participants (39.4% of PEDs, 44.3% of GP&FPs and 14.7% of ENTs) stated that pneumatic otoscopy is essential for AOM diagnosis. Regarding the most common etiological agents of AOM in children, 54.2% of PEDs, 51.4% of FP&GPs and 57.4% of ENTs stated that the most common causative agents of AOM are Streptococcus pneumoniae and non-typeable Haemophilus influenzae. Nearly 76% of participants indicated they use direct antibiotic therapy when they diagnose AOM in certain situations. The first-line choice of antibiotic therapy is amoxicillin clavulanate, and 67% of participants prefer to use antibiotic therapy for 7-10 days. Approximately 31% of all participants stated that "viruses" are the main cause of AOM; however, 62% of these participants reported using antibiotic therapy. In comparison, 32% participants from private clinics prefer to treat AOM primarily with observation, a rate that is significantly higher than that of other clinical settings. Physicians who prefer to use observation strategy also prefer the combination of paracetamol and NSAIDs. Approximately 41% of participants have undergone postgraduate medical education on the topic of AOM. In total, 73% of all participant physicians believe that otitis media is a vaccine-preventable disease. With the information from all of the participants, the calculated mean cost per case of AOM is 28 ± 4 USD. In Turkey, the estimated incidence of AOM is 24,000-33,000 cases per 10,000 children <5 years of age (1,820,000-2,100,000 cases per year), and the estimated total cost of AOM is 61,152,000 USD (not including acute otitis media-related complications and otitis media-related hospitalizations).

CONCLUSION

The medical and economic burden of AOM to the health economics in Turkey is considerable. Specific educational programs and evidence-based national guidelines concerning AOM should be implemented. Improving diagnostic accuracy with education will lead to improved management, judicious use of antibiotics, decreased antibiotic resistance, and potential economic benefits. A more prudent use of antibiotics would also lower the economic burden of this disease. Vaccination seems to be promising for the prevention of AOM.

The burden of nonencapsulated Haemophilus influenzae in children and potential for prevention

PURPOSE OF REVIEW

In countries with established Haemophilus influenzae serotype b (Hib) immunization programmes, nonencapsulated H. influenzae (ncHi) is responsible for most invasive H. influenzae infections across all age groups and is associated with higher case fatality. A pneumococcal conjugate vaccine has recently been licensed, which may potentially also protect against invasive H. influenzae infections.

RECENT FINDINGS

Invasive ncHi disease is uncommon in childhood but has a much higher incidence in the first month of life. Most neonates with invasive ncHi infections are born prematurely and develop septicaemia in the first 48 h of life which can be fatal. After this period, invasive ncHi incidence falls rapidly and remains low throughout childhood. Most infants and children who develop invasive ncHi disease have significant underlying comorbidities, particularly neurological disease, malignancy and other conditions requiring immunosuppressive therapy. Although characteristically associated with respiratory tract infections, at least a quarter of invasive ncHi infections present with meningitis.

SUMMARY

A vaccine against ncHi could have an important preventive role in children with comorbidities. Future studies should focus on assessing specific risk factors for neonatal and childhood ncHi disease and long-term outcomes of children with invasive ncHi meningitis.

Use of the 13-valent pneumococcal conjugate vaccine in infants and young children

INTRODUCTION

The inclusion of the heptavalent pneumococcal conjugate vaccine (PCV7) in the immunization schedule of infants and young children has greatly reduced the incidence of invasive and non-invasive diseases due to Streptococcus pneumoniae. However, as PCV7 has some limitations, new vaccines containing more pneumococcal serotypes have been developed. Only two of these have so far reached the market: a 10-valent preparation containing the PCV7 serotypes plus serotypes 1, 5 and 7F (PCV10), and a 13-valent vaccine containing the PCV7 serotypes plus serotypes 1, 3, 5, 6A, 7F and 19A (PCV13).

AREAS COVERED

The main aim of this review is to discuss the reasons that have led to the formulation of PCV13, its immunogenicity, safety and tolerability and the recommendations concerning its use in children.

EXPERT OPINION

There is no doubt that a pneumococcal conjugate vaccine with the composition of PCV13 has significantly increased the possibility of preventing pneumococcal disease. Its immunogenicity, safety and tolerability seem to be optimal, as does its cost-effectiveness. However, despite these favorable premises, it cannot be considered the final preparation for the prevention of pneumococcal disease, and it is likely that a new vaccine capable of covering all pneumococcal serotypes will be needed in the future.

The future of pneumococcal disease prevention

Pneumococcal disease (PD) is the leading cause of vaccine preventable deaths in children <5 years of age worldwide, with most of the deaths occurring in the developing world. Prevention of PD in children has been achieved by vaccination with pneumococcal conjugate vaccine (PCV), the basis for which is induction of a protective antibody response against the bacterial polysaccharide capsule. Conjugation of the polysaccharide capsule to a protein carrier enables the generation of an immunologic response to the vaccine in young children, leading to protection against infection. The heptavalent PCV, which contains 7 of the 93 known pneumococcal serotypes (4, 6B, 9V, 14, 18C, 19F, 23F) was the first PCV available, licensed in the US in 2000 and subsequently in many countries worldwide, including Latin American and Caribbean countries. Since its introduction, PCV7 has been documented effective for reducing invasive PD mortality and burden, as well as that of pneumonia and otitis media. Additionally, PD caused by the vaccine serotypes has decreased in the unimmunized population due to herd immunity induced by PCV7. Despite this success, significant disease burden still exists globally due to serotypes not included in PCV7. Currently there are 2 new PCVs that have been approved for use in children, a 10-valent vaccine (includes PCV7 serotypes plus serotypes 1, 5 and 7F) and a 13-valent vaccine (includes PCV7 serotypes plus serotypes 1, 3, 5, 6A, 7F and 19A). The selection of new serotypes to be included was based on importance of these serotypes as causes of PD. An additional 15-valent vaccine (includes PCV 7 serotypes plus serotypes 1, 3, 5, 6A, 7F, 19A, 22F and 33F) is undergoing clinical trial testing. In view of the 93 serotypes that are currently known, it seems clear that vaccines with greater coverage, likely based on proteins common to all serotypes, will be needed in the future. Technical and regulatory challenges to the development and approval of newer PCVs include a need for licensing criteria of common protein vaccines, establishment of correlates of protection for disease manifestations other than invasive disease, comparative efficacy data, and clinical trial testing of concomitant immunization of higher valency PCVs with other vaccines.

The design of semi-synthetic and synthetic glycoconjugate vaccines

INTRODUCTION

Glycoconjugate vaccines are among the safest and most efficacious vaccines developed during the last 30 years. They are a potent tool for prevention of life-threatening bacterial infectious diseases like meningitis and pneumonia. The concept of hapten-carrier conjugation is now being extended to other disease areas.

AREAS COVERED

This is an overview of the history and current status of glycoconjugate vaccines. The authors discuss the approaches for their preparation and quality control as well as those variables which might affect their product profile. The authors also look at the potential to develop fully synthetic conjugate vaccines based on the progress of organic chemistry. Additionally, new applications of conjugate vaccines technology in the field of non-infectious diseases are discussed. Through this review, the reader will have an insight regarding the issues and complexities involved in the preparation and characterization of conjugate vaccines, the variables that might affect their immunogenicity and the potential for future applications.

EXPERT OPINION

The immunogenicity of weak T-independent antigens can be increased in quantity and quality by conjugation to protein carriers, which provide T-cell help. Glycoconjugate vaccines are among the safest and most efficacious vaccines developed so far. Various conjugation procedures and carrier proteins can be used. Many variables impact on the immunogenicity of conjugate vaccines and a tight control through physicochemical tests is important to ensure manufacturing and clinical consistency. New and challenging targets for conjugate vaccines are represented by cancer and other non-infectious diseases.

Impact of conjugate pneumococcal vaccines on the changing epidemiology of pneumococcal infections

Streptococcus pneumoniae-related infections have a major global impact on healthcare, especially in the developing world, and are considered the number one vaccine-preventable cause of death in children. There are more than 90 pneumococcal serotypes and 46 serogroups. The first capsular polysaccharide pneumococcal vaccine was licensed in the USA in 1977 for individuals older than 2 years of age at high risk for pneumococcal disease. Two decades later, the first 7-valent pneumococcal polysaccharide-protein conjugate vaccine completed the required clinical trials and was introduced as part of the national immunization program of various countries. New-generation vaccines that include emerging serotypes, while maintaining protection against the 7-valent pneumococcal serotypes, have recently been approved. With the addition of these serotypes, the majority of potential pneumococcal serotypes causing invasive disease in most parts of the world could be covered.

6th World Congress of the World Society for Pediatric Infectious Diseases (WSPID)

The 6th World Congress of the World Society for Pediatric Infectious Diseases (WSPID) was held in Buenos Aires, Argentina between 18 and 22 November, 2009. This is one of the biggest pediatric infectious disease assemblies in the world and it brought together pediatricians and pediatric infectious disease and vaccine experts. Numerous topics about pediatric infectious diseases were discussed during the congress. The scientific program focused on vaccines and vaccine-preventable diseases, including epidemiological and vaccine efficacy trials and updates on topics of childhood infectious disease. We summarize the current knowledge about some childhood vaccines and vaccine-preventable diseases, including rotavirus vaccines, conjugated pneumococcal vaccines (PCV-7, PHiD-CV and PCV-13), varicella, pertussis meningococcal and pandemic H1N1 vaccines. The next WSPID congress will be held in Melbourne, Australia between 16 and 20 November 2011.