Use of pneumococcal polysaccharide vaccines: no simple answers

Adult immunization with 13-valent pneumococcal vaccine in Campania region, South Italy: an economic evaluation

Pneumococcal pneumonia has a high clinical burden in terms of morbidity, mortality and hospitalization rate, with heavy implications for worldwide health systems. In particular, higher incidence and mortality rates of community-acquired pneumonia (CAP) cases, with related costs, are registered among elderly. This study aimed to an economic evaluation about the immunization with PCV13 in the adult population in Campania region, South Italy. For this purpose we performed, considering a period of 5 y, a budget impact analysis (BIA) and a cost-effectiveness analysis which considered 2 scenarios of immunization compared with lack of immunization for 2 targeted cohorts: first, the high risk subjects aged 50-79 y, and second the high risk individuals aged 50-64 y, together with all those aged 65 y. Regarding the first group, the decrease of pneumonia could give savings equal to €29,005,660, while the immunization of the second cohort could allow savings equal to €10,006,017. The economic evaluation of pneumococcal vaccine for adult groups represents an essential instrument to support health policies. This study showed that both hypothesized immunization strategies could produce savings. Obtained results support the use of pneumococcal conjugate vaccine for adults. This strategy could represent a sustainable and savings-producer health policy.

Post-splenectomy and hyposplenic states

The spleen is crucial in regulating immune homoeostasis through its ability to link innate and adaptive immunity and in protecting against infections. The impairment of splenic function is defined as hyposplenism, an acquired disorder caused by several haematological and immunological diseases. The term asplenia refers to the absence of the spleen, a condition that is rarely congenital and mostly post-surgical. Although hyposplenism and asplenia might predispose individuals to thromboembolic events, in this Review we focus on infectious complications, which are the most widely recognised consequences of these states. Because of the high mortality, the fulminant course, and the refractoriness to common treatment of overwhelming infections caused by encapsulated bacteria, prevention through vaccination and antibiotic prophylaxis is the basis of the management of patients who have had splenectomy or have hyposplenism. In this Review, we critically assess clinical and diagnostic aspects of splenic dysfunction and highlight new perspectives in the prevention of overwhelming post-splenectomy infections.

Inhaled delivery of 23-valent pneumococcal polysaccharide vaccine does not result in enhanced pulmonary mucosal immunoglobulin responses

We compared the effect of intramuscular vs. inhaled 23-valent pneumococcal capsular polysaccharide vaccine (23-PPV) on pulmonary mucosal immunoglobulin levels. Bronchoalveolar lavage (BAL) and serum were collected from 33 adults before and 1 month after injected (n = 16) or inhaled (n = 17) 23-PPV. Levels of pneumococcal capsule-specific IgG and IgA to types 1, 9V and 14 were measured in each sample. Injected 23-PPV produced a significant increase in types 1, 9V and 14 capsule-specific IgG and type 1 IgA in both serum and BAL (type 1 geometric mean BAL IgG 9.8 ng/ml post-vaccine vs. 5 ng/ml pre-vaccine, p = 0.01; type 9V geo mean 5.6 ng/ml vs. 2.7 ng/ml, p = 0.001; type 14 geo mean 23.6 ng/ml vs. 6.2 ng/ml, p = 0.02). Inhaled vaccine produced no response in either BAL or serum.

Development and function of the mammalian spleen

The vertebrate spleen has important functions in immunity and haematopoiesis, many of which have been well studied. In contrast, we know much less about the mechanisms governing its early embryonic development. However, as a result of work over the past decade-mostly using knockout mice--significant progress has been made in unravelling the genetic processes governing the spleen's early development. Key genetic regulators, such as Tlx1 and Pbx1, have been identified, and we know some of the early transcriptional hierarchies that control the early patterning and proliferation of the splenic primordium. In mouse and humans, asplenia can arise as a result of laterality defects, or the spleen can be absent with no other discernible abnormalities. Surprisingly, given the spleen's diverse functions, asplenic individuals suffer no major haematopoietic or immune defects apart from a susceptibility to infection with encapsulated bacteria. Recent evidence has shed light on a previously unknown role of the spleen in the development and maintenance of specific B cell populations that are involved in the initial response to infection caused by encapsulated bacteria. The lack of these populations in asplenic mice and humans may go some way to explaining this susceptibility.

Invasive pneumococcal disease in adults in North-Rhine Westphalia, Germany, 2001-2003

A population-based survey of invasive pneumococcal disease (IPD) was conducted among adults in North-Rhine Westphalia, Germany. The study included 202 of the 386 hospitals in the region, together with the 27 microbiological laboratories that submitted reports of IPD in these hospitals to the National Reference Centre for Streptococci. The reports of 16 laboratories were comprehensively reviewed. Most (95.8%) IPD isolates were susceptible to penicillin G, but 14.5% were resistant to clarithromycin. Serotypes 14 (15.6%), 3 (9.3%), 4 (7.1%) and 7F (7.9%) were the most common. The serotype coverage of the 23-valent pneumococcal polysaccharide vaccine was 80.8%. During 2001-2003, the annual incidence of IPD, after correcting for laboratory and hospital under-reporting, was 16.2/100 000 in individuals aged >or= 65 years. In three university hospitals, blood cultures were obtained for only 37% of patients with community-acquired pneumonia, and fewer than one-third of such cultures were obtained in one hospital before antibiotics were prescribed, suggesting that the true incidence of IPD was closer to 50/100 000.

Preventing pneumonia: the role for pneumococcal and influenza vaccines

Streptococcus pneumoniae and influenza cause a wide spectrum of illness and result in substantial morbidity and mortality. They are significant public health concerns, and vaccines against both organisms exist. The pneumococcal polysaccharide vaccine has been available in its current form for over 20 years. Nonetheless, definitive evidence from prospective trials of its efficacy is lacking. Experts recommend that patients at high risk for pneumococcal infection and complications from this process be vaccinated. The role for revaccination remains controversial. Traditional influenza vaccine is composed of three virus types and decreases rates of serologically confirmed cases of influenza, hospital admissions for respiratory infection, and mortality. The pneumococcal and influenza vaccines are considered cost-effective options for pneumonia prevention.

Pneumococcal infections in HIV infected adults--clinical features, reasons behind the association and future hopes for prevention

Streptococcus pneumoniae is the most important bacterial cause of pneumonia and meningitis among adults world wide. It is a particularly common cause of these infections and also bacteraemia among HIV infected adults with rates of disease increasing to more than 100 times the normal as HIV infection progresses to AIDS. This article briefly describes the common presentations and outcomes of pneumococcal disease (PD) in HIV infected adult inpatients in Malawi. Factors underlying susceptibility to pneumococcal infection in HIV infected adults are then reviewed, along with the effectiveness of current vaccines. Finally, novel approaches that will be needed to combat PD in HIV afflicted parts of the world are suggested.

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.

Peripheral development of B cells in mouse and man

In man and in mouse, B-cell maturation occurs in steps, first in the bone marrow from hematopoietic precursors to immature/transitional B cells, then in the periphery from transitional to fully mature B cells. Each developmental step is tightly controlled by the expression and function of the B-cell receptor (BCR) and by the ability to interact with the microenvironment. Mature B cells collaborate with T cells in the adaptive immune response, leading to the production of high-affinity antibodies. This response is very accurate, but slow. Immediately after pathogen entry, however, antibodies already present in the serum reinforce the innate immune response and contribute to the first-line defense against infection. Low-affinity natural antibodies are produced by B-1a B cells in the mouse and immunoglobulin M (IgM) memory cells in man. These antibodies represent an immediate protection against all microorganisms and the only one against encapsulated bacteria. B-1a and IgM memory B cells may function as a link between the innate and adaptive immune response and thus perform a primordial B-cell function.