Pneumococcal immunisation in the 21st century

Development and evaluation of a novel vaccine against prevalent invasive multi-drug resistant strains of Streptococcus pneumoniae

Streptococcus pneumoniae is a pathogen that causes serious invasive infections, such as septicemia, meningitis and pneumonia in addition to mild upper respiratory tract infections. Protection from pneumococcal diseases is thought to be mediated mainly by serotype-specific antibodies to capsular antigens. Pneumococcal conjugate vaccine consists of sugars (polysaccharides) from the capsule of the bacterium S. pneumoniae that are conjugated to a carrier protein. Three pneumococcal conjugated vaccines, each directed against a group of serotypes, are registered in Egypt; however, local vaccine production is required to cover the most prevalent serotypes. In this work, capsular polysaccharide from the most current and prevalent serotypes in Egypt were extracted, purified and conjugated to bovine serum albumin (BSA). The polysaccharide protein conjugate was purified through ultrafiltration technique and molecular size distribution was compared to an available vaccine. The immunogenicity of the prepared vaccine was examined via two methods: First, by measuring the levels of the elicited antibodies in the sera of the vaccinated mice; second, by challenging the vaccinated groups of mice with approximately 107 CFU of each specific serotype and determining the degree of protection the developled vaccine offers. Our results show that the developed conjugated capsular polysaccharide vaccine is highly immunogenic and protective in mice. This finding illustrates the importance of tracking the most recent and predominant peneumococcal serotypes to generate effective vaccines, instead of using expensive imported vaccines with large number of serotypes which might not be even present in the community.

Pneumococcal vaccines for children: a global public health priority

Pneumococcal conjugated vaccines have been recommended in children for over a decade in many countries worldwide. Here we review the development of pneumococcal vaccines with a focus on the two types currently available for children and their safety record. We discuss also the effect of vaccines, including the 13-valent pneumococcal conjugate vaccine, on invasive pneumococcal diseases in children, particularly bacteraemia, pneumonia and meningitis, as well as on mucosal disease and carriage. In regions where immunization was implemented in young children, the number of invasive pneumococcal diseases decreased significantly, not only in the target age group, but also in younger and much older subjects. Challenges and future perspectives regarding the development of new 'universal' vaccines, which could bypass the current problem of serotype-specific protection in a context of serotype replacement, are also discussed.

Pneumococcal serotype distribution in invasive paediatric disease in Southern Finland before the introduction of vaccine

Vaccination with pneumococcal conjugate vaccines (PCV) has been started in many countries, resulting in a marked decrease in the incidence of invasive pneumococcal disease (IPD). After the decline, an increase in the incidence of IPD caused by non-vaccine serotypes has been observed. Finland has just decided to incorporate PCV into the national immunization programme, starting 1 September 2010. We describe the patients treated for IPD in one hospital in Finland before the use of PCV. Details of patients treated for IPD at the Children's Hospital, University of Helsinki between 2002 and 2007, were sought using the hospital discharge register and laboratory data. In total 118 cases of IPD were diagnosed in 113 children between 1 January 2002 and 31 December 2007. The yearly number of cases of IPD increased from 10 in 2002 to 26 in 2007. There were 5 deaths, all in patients with meningitis (5/19, 26%), and the total mortality was 4% (5/113). Seventy-five (77%) of the 97 pneumococcal isolates for which serotype was available were covered by the 7-valent PCV; 77% were also in the 10-valent PCV and 91% in the 13-valent PCV. Considering the serotype distribution of the pneumococcal isolates, a marked benefit is expected from including PCV in the vaccination programme.

Community-acquired bacterial meningitis in elderly patients: experience over 30 years

Clinical characteristics, etiologies, evolution, and prognostic factors of community-acquired bacterial meningitis in elderly patients are not well known. To improve this knowledge, all episodes of community-acquired bacterial meningitis were prospectively recorded and cases occurring in patients >or=65 years old were selected. During the period 1977-2006, 675 episodes in adults (aged >or=18 yr) were recorded, with 185 (27%) in patients aged >or=65 years old; 76 were male and 109 were female, with a mean age of 73 +/- 6 years (range, 65-93 yr). Causative microorganisms were Streptococcus pneumoniae 74, Neisseria meningitidis 49, Listeria monocytogenes 17, other streptococcal 9, Escherichia coli 6, Haemophilus influenzae 4, Klebsiella pneumoniae and Staphylococcus aureus 2 each, Capnocytophaga canimorsus and Enterococcus faecalis 1 each, and unknown in 20. On admission 91% had had fever, 32% were in a coma (Glasgow Coma Scale <or=8), 9% presented with seizures, and 8% with shock. Thirty patients (16%) presented with seizures during therapy. Mortality was 58/185 (31%). Compared with patients aged 18-65 years, there were significant differences among older patients (aged >or=65 yr), who showed a higher frequency of diabetes and malignancy as underlying disease; pneumonia, otitis, and pericranial fistula as predisposing factors; and S. pneumoniae and L. monocytogenes as etiology. There were also differences in clinical presentation, complications, sequelae, and mortality. Factors independently related with mortality were age, pneumonia as a predisposing factor, coma on admission, and heart failure and seizures after therapy. Dexamethasone therapy was a protective factor. In conclusion, bacterial meningitis in elderly patients is associated with greater diagnostic difficulties and neurologic severity and more complications, as well as with increased mortality. Antiseizure prophylaxis might be useful in these patients.