Conjugated heptavalent pneumococcal vaccine

Prospects for a vaccine against otitis media

Otitis media is a major cause of morbidity in 80% of all children less than 3 years of age and often goes undiagnosed in the general population. There is evidence to suggest that the incidence of otitis media is increasing. The major cause of otitis media is infection of the middle ear with microbes from the nasopharynx. The anatomical orientation of the eustachian tube, in association with a number of risk factors, predisposes infants and young children to the infection. Bacteria are responsible for approximately 70% of cases of acute otitis media, with Streptococcus pneumoniae, nontypeable Haemophilus influenzae and Moraxella catarrhalis predominating as the causative agents. The respiratory viruses, respiratory syncytial virus, rhinovirus, parainfluenza and influenza, account for 30% of acute otitis media cases. Over the past decade, there has been a profound increase in the reported resistance to antibiotics, which, with increased disease burden, has focussed attention on vaccine development for otitis media. A polymicrobial formulation containing antigens from all major pathogens would have the greatest potential to deliver a sustained reduction in the disease burden globally. The disappointing outcomes for otitis media seen with the polysaccharide pneumococcal conjugate vaccine have raised major challenges for the vaccination strategy. Clearly, more knowledge is required concerning immune mechanisms in the middle ear, as well as vaccine formulations containing antigens that are more representative of the polymicrobial nature of the disease. Antigens that have been extensively tested in animal models are now available for testing in human subjects.

Prevnar 13, the New 13-Valent Pneumococcal Conjugate Vaccine

Objective:

To review the immurtogenicity, efficacy, and safety of the 13-valent pneumococcal conjugate vaccine (PCV13) for use in pediatric patients.

Data Sources:

A MEDLINE search (2000-September 2011) was conducted using the key words Streptococcus pneumoniae and pneumococcal conjugate vaccine for clinical trials, limited to studies conducted in humans and published in English.

Studv Selection And Data Extraction:

Randomized, controlled, multicenter trials were reviewed and included to evaluate the safety and efficacy of PCV13, Literature on the epidemiology and pathology of pneumococcal Infections and recommendations from the Advisory Committee on Immunization Practices (ACIP) were also reviewed.

Data Synthesis:

PCV13 is approved for routine vaccination of all infants as a 4-dose series at age 2,4,6, and 12–15 months for children who previously received 1 or more doses of the 7-valent pneumococcal conjugate vaccine (PCV7), and for children with underlying medical conditions that increase their risk for pneumococcal disease or its complications. PCV13 has comparable immunogenicity to the serotypes common with PCV7 and also provides protection against 6 additional pneumococcal serotypes. PCV13 has also been shown to have a comparable adverse reaction profile to PCV7.

Conclusions:

Based on published immunogenicity and safety data, as well as the recent recommendations by the ACIP for routine use in infants and indications for high-risk pediatric patients, PCV13 is a revised formulation of pneumococcal vaccine that should be included on pharmacy formularies.

Nasopharyngeal carriage rate of Streptococcus pneumoniae in children with sickle cell disease before and after the introduction of heptavalent pneumococcal conjugate vaccine

Children with sickle cell disease (SCD) are at high risk of severe infection with Streptococcus pneumoniae (SP). From 2002, all children aged <5 years in the UK with SCD were recommended 7-valent pneumococcal conjugate vaccine (PCV-7) in infancy and 23-valent pneumococcal polysaccharide vaccine boosting, in addition to regular penicillin prophylaxis. Our objective was to determine the nasopharyngeal (NP) carriage rate of SP in children aged <5 years with SCD before and after vaccination with PCV-7 (by vaccine, cross-protection and non-vaccine serotypes). NP swabs were obtained from 63 children attending the Royal London Hospital or Newham General Hospital paediatric haematology clinic between April 2001 and April 2002. Later, NP swabs were obtained from 43 children attending the clinic between June and December 2004 after a PCV-7 vaccination programme. All SP isolated by culture were serotyped and susceptibility to penicillin measured. In the first study group, 13 samples grew SP with 1 sample containing 2 different serotypes, giving a carriage rate of 21%. Four (31%) were intermediately susceptible to penicillin. In the second group overall NP carriage rate had decreased to 9% (n=4), and the proportion directly or indirectly covered by the PCV-7 vaccine fell from 13/14 to 2/4 (P=0.11). One (25%) of these isolates was intermediately susceptible to penicillin. The introduction of PCV-7 appears to be associated with a shift in distribution of serotypes carried by children with SCD. This may have implications for vaccine effectiveness.

Randomised revaccination with pneumococcal polysaccharide or conjugate vaccine in asplenic children previously vaccinated with polysaccharide vaccine

OBJECTIVE

Asplenic children are at high risk of invasive pneumococcal infection. In this group, the American Academy of Pediatrics recommends a single revaccination with the 23-valent polysaccharide vaccine (PSV23) 3-5 years after a previous PSV23 dose. Despite potential advantages, there are few data available regarding the safety and immunogenicity of the heptavalent pneumococcal conjugate vaccine (PCV7) in this population. The aim of the study was to prospectively determine and to compare, in asplenic children, the vaccine specific antibody titres against the seven serotypes included in the PCV7 after administration of one dose of PCV7 or of PSV23, 3 years or more after an initial vaccination with PSV23.

PATIENTS AND METHODS

In this randomised, single-centre study, antibody titres were monitored at baseline, at 1 and 6 months after revaccination in 21 children with anatomic or functional asplenia. Response was considered as positive when there was a four-fold increase in antibody titres from baseline.

RESULTS

The most frequently reported adverse events were local reactions in 7/11 of PCV7 subjects and in 5/8 of PSV23 subjects, and general reactions (loss of appetite, sleepiness) in 5/11 of PCV7 subjects and in 1/8 of PSV23 subjects; without any serious adverse events. One child in the PCV7 group had increased temperature (38.4 degrees C). At least half of the PCV7 children responded to four or five serotypes, while more than half of the PSV23 subjects responded to less than 3 serotypes (p=0.285). After 1 month, the immune response for serotype 23F was significantly greater after PCV7 vaccination than after PSV23 vaccination (p=0.036).

CONCLUSIONS

PCV7 revaccination is safe and immunogenic in asplenic children previously vaccinated with PSV23, and could provide appropriate booster response in this high-risk population. The clinical repercussion on invasive pneumococcal diseases remains to be demonstrated.

Vaccines based on the cell surface carbohydrates of pathogenic bacteria

Glycoconjugate vaccines, in which a cell surface carbohydrate from a micro-organism is covalently attached to an appropriate carrier protein are proving to be the most effective means to generate protective immune responses to prevent a wide range of diseases. The technology appears to be generic and applicable to a wide range of pathogens, as long as antibodies against surface carbohydrates help protect against infection. Three such vaccines, against Haemophilus influenzae type b, Neisseria meningitidis Group C and seven serotypes of Streptococcus pneumoniae, have already been licensed and many others are in development. This article discusses the rationale for the development and use of glycoconjugate vaccines, the mechanisms by which they elicit T cell-dependent immune responses and the implications of this for vaccine development, the role of physicochemical methods in the characterisation and quality control of these vaccines, and the novel products which are under development.

Pneumococcal conjugate vaccines for preventing vaccine-type invasive pneumococcal disease and pneumonia with consolidation on x-ray in children under two years of age

BACKGROUND

Pneumonia, most commonly caused by Streptococcus pneumoniae (Pnc), is a major cause of morbidity and mortality among young children especially in developing countries. Recently, the prevalence of antibiotic-resistant Pnc has increased worldwide such that the effectiveness of preventive strategies, like the new pneumococcal conjugate vaccines (PCV) on rates of invasive pneumococcal disease (IPD) and pneumonia, needs to be evaluated.

OBJECTIVES

To determine the efficacy of PCV in reducing the incidence of IPD due to vaccine serotypes (VT) and x-ray confirmed pneumonia with consolidation of unspecified etiology in children who received PCV before 12 months of age.

SEARCH STRATEGY

We searched the following databases: the Cochrane Central Register of Controlled Trials (CENTRAL) (The Cochrane Library, Issue 1 2004), MEDLINE (1990 to March 2004) and EMBASE (1990 to December 2003). Reference list of articles, and books of abstracts of relevant symposia, were hand searched. Researchers in the field were also contacted.

SELECTION CRITERIA

Randomised controlled trials (RCTs) comparing PCV with placebo, or another vaccine, among children below two years with IPD and clinical/radiographic pneumonia as outcomes.

DATA COLLECTION AND ANALYSIS

Two reviewers independently identified eligible studies, assessed trial quality, and extracted data. Differences were resolved by discussion. The inverse variance method was used to pool effect sizes.

MAIN RESULTS

We identified four trials assessing the efficacy of PCV in reducing the incidence of IPD, two on x-ray confirmed pneumonia as outcome, and one on clinical pneumonia, with or without x-ray confirmation. Results from pooling HIV-1 negative children from the South African study with the other studies were as follows: the pooled vaccine efficacy (VE) for vaccine-type IPD was 88% (95% confidence interval (CI) 73% to 94%; fixed effect and random effects models), the effect measure was statistically significant (p <0.00001) and there was no heterogeneity (p = 0.77I2 0%); the pooled VE for all-serotype IPD was 66% (95% CI 46% to 79%; fixed effect model), the effect measure was statistically significant (p <0.00001) and there was no statistical heterogeneity (p = 0.09, I2 51%); the pooled VE for x-ray confirmed pneumonia was 22% (95% CI 11% to 31%; both fixed effect and random effects models) and there was no statistical heterogeneity (p = 0.80, I2 0%). Analyses that included all the children in the South African study (HIV-1 negative and HIV-1 positive children) and pooled with data from the other studies gave very similar results.

REVIEWERS' CONCLUSIONS

PCV is effective in reducing the incidence of IPD from all serotypes but exerts a greater effect in reducing VT IPD. Although PCV is also effective in reducing the incidence of x-ray confirmed pneumonia, there are still uncertainties about the definition of this outcome. Additional randomised controlled trials are currently in progress.