Enhanced antibody response to pneumococcal polysaccharide vaccine after prior immunization with conjugate pneumococcal vaccine in HIV-infected adults

Pneumococcal Conjugate Vaccination Followed by Pneumococcal Polysaccharide Vaccination in Lung Transplant Candidates and Recipients

Background

Pneumococcal conjugate vaccination as well as pneumococcal polysaccharide vaccination are recommended for lung transplant candidates and recipients, but the combination of these vaccines has not been extensively studied in these specific populations.

Methods

Lung transplant candidates and recipients were vaccinated with a 13-valent pneumococcal conjugate vaccine, followed 8 weeks later by a pneumococcal polysaccharide vaccine. Pneumococcal antibody levels against 13 pneumococcal serotypes were measured and followed up after 1 year in the transplant recipients. These values were compared with a historical control group vaccinated with the polysaccharide vaccine alone.

Results

Twenty-five lung transplant candidates and 23 lung transplant recipients were included. For the majority of serotypes, there was no significant increase in antibody levels after additional vaccination with the polysaccharide vaccine in both patient groups. When compared with the historical control group, the antibody response in lung transplant recipients 1 year after vaccination did not seem to have improved by vaccination with both vaccines instead of the polysaccharide vaccine alone.

Conclusions

Serologic vaccination responses in lung transplant candidates and recipients were not improved by giving a 23-valent pneumococcal polysaccharide vaccine after a 13-valent pneumococcal conjugate vaccine. The benefit of this vaccination schedule in lung transplant recipients seems to differ from other immunocompromised populations. The optimal vaccination schedule for lung transplant candidates and recipients remains to be determined.

Pneumococcal vaccination in adult people living with HIV on suppressive antiretroviral therapy: a case-control study

There is little information on the effectiveness of the pneumococcal vaccines (PVs), especially for the pneumococcal conjugate vaccines (PCVs), in HIV-infected patients in the modern antiretroviral era. This is a case–control study where cases were people living with HIV (PLWH) with confirmed pneumococcal infection (CPI) and controls were PLWH without CPI matched with cases by gender and year of HIV diagnosis. The selection process was blinded to the study factor (vaccination). Sample size estimation yielded 61 cases and 183 controls. We analyzed the effect of PV on CPI using Cox proportional-hazards regression model with time-dependent covariates. We included 256 subjects: 64 cases, and 192 controls. PVs had been administered to 115 (45%) patients. Only the modified Charlson Comorbidity Index (HR 1.16, 95%CI 1.06–1.27, P = 0.001) and the CD4 nadir (HR 0.99, 95% CI 0.98–0.99, P = 0.001) were independently associated with CPI. Receipt of PV was not associated with CPI after adjusting in the multivariate model with time protection as a dependent covariate (HR 0.65, 95% CI 0.35–1.32 P = 0.250). We also investigated the influence of different immunization schedules. In an adjusted model, we found no evidence of protection against CPI, including double immunization schedules (HR 0.42 95%CI 0.15–1.19 P = 0.102). In this case–control study, we could not show an association between pneumococcal vaccination and confirmed pneumococcal infection, although a protective effect of particular schedules of immunization cannot be ruled out.

Long-Term Serological Response to 13-Valent Pneumococcal Conjugate Vaccine Versus 23-Valent Polysaccharide Vaccine in HIV-Infected Adults

INTRODUCTION

Long-term comparative immunologic response to 13-valent pneumococcal conjugate vaccine (PCV13) versus 23-valent polysaccharide vaccine (PPV23) among HIV-infected adults has not yet been investigated.

METHODS

In this prospective pilot study, we quantified in HIV-positive adults serotype-specific IgG concentrations of the 12 pneumococcal serotypes shared by both vaccines 5 years after vaccination with two doses of PCV13 8 weeks apart (group 1) or one dose of PPV23 (group 2) and compared them with those assessed prior to vaccination (BL) and after 1 year (T1). Comparison of immunogenicity was based on geometric mean concentration (GMC), proportion of individuals with ≥ twofold increase from BL in specific antibody concentration against ≥ 2 serotypes and percentage of individuals with serotype-specific IgG ≥ 0.35 μg/ml, ≥ 1 μg/ml and ≥ individual serotype-specific correlates of protection.

RESULTS

We included 91 subjects (median CD4+ 650 cells/µl, > 90% with HIV-RNA < 50 copies/ml); patients in groups 1 (n = 42) and 2 (n = 49) were homogeneous for the main characteristics. GMCs were significantly higher in the PCV13 group than in the PPV23 group for serotype 19F (p = 0.003). Both vaccines revealed higher significant GMCs to most serotypes compared with BL, i.e., eight in group 1 vs. seven in group 2. With respect to T1, GMCs decreased significantly in the PCV13 group for eight vs. ten serotypes in the PPV23 group. More participants in the PCV13 group had ≥ 2 increase from BL in antibody levels to ≥ 2 serotypes compared with the PPV23 group (78.6% vs. 59.2%, p = 0.042). Overall, the percentage of subjects with serotype-specific IgG ≥ 0.35 μg/ml, ≥ 1 μg/ml and ≥ individual serotype-specific correlates of protection was similar between groups.

CONCLUSION

In this study with HIV-positive adults with a favorable viro-immunologic profile, both vaccines were shown to achieve a long-term durable serologic response. We found minor differences in immunogenicity between the two vaccines, which favored PCV13 over PPV23 5 years after immunization.

TRIAL REGISTRATION

ClinicalTrials.gov identifier, NCT02123433.

Vaccination in the Adult Patient Infected with HIV: A Review of Vaccine Efficacy and Immunogenicity

Patients infected with HIV remain at increased risk of mortality and morbidity from diseases that are preventable with vaccines partly due to the persisting immunopathology that results in impaired responses to vaccination despite virologic suppression. Because data on clinical effectiveness in patients who are immunocompromised remain limited, undervaccination of individuals with HIV poses a major concern. Multiple societies have published recommendations on vaccination in individuals infected with HIV. Many of these recommendations are based on extrapolation of data from clinical trials that usually exclude patients with HIV, although there is a growing body of data from patients infected with HIV as well. In this review, we describe the available literature on vaccine response in the adult patient with HIV as measured by immunogenicity or vaccine efficacy.

HIV-related pneumococcal disease prevention in adults

INTRODUCTION

HIV-infected persons are particularly susceptible to the development of severe pneumococcal disease, even in the setting of combination antiretroviral therapy (cART), due to slow, incomplete recovery of anti-pneumococcal host defenses. This risk is increased by avoidable aspects of lifestyle, particularly smoking, which intensify immunosuppression. Clearly, more effective preventive measures are needed to counter this threat. Areas covered: This is a detailed review of the published literature focusing on currently available strategies for prevention of pneumococcal infection in HIV-infected patients, including cotrimoxazole prophylaxis, cART, pneumococcal vaccination, and smoking cessation strategies. This is preceded by a consideration of the epidemiology, clinical presentation, risk factors, and outcome of pneumococcal disease. Expert commentary: Cotrimoxazole prophylaxis has been shown to reduce morbidity and mortality in HIV-infected patients, although there is inconsistent data on the preventive efficacy against pneumococcal infections. Some recent studies have documented unchanged incidences of IPD in adult patients in the cART era. With regard to pneumococcal vaccination, routine acceptance of the efficacy of the PCV13/PPV23 sequential administration prime-boost strategy awaits the outcome of clinical trials in those with HIV infection. Smoking cessation, and discontinuation of excessive alcohol consumption and intravenous drug abuse, are priority strategies to prevent severe pneumococcal infection.

Association of time since pneumococcal polysaccharide vaccine receipt and CD4 count with antibody response to the 13-valent pneumococcal conjugate vaccine in HIV-infected adults

INTRODUCTION

Pneumococcal infection is a leading cause of illness and death in HIV-infected adults. Current United States guidelines for HIV-infected adults recommend a single dose of the 13-valent pneumococcal conjugate vaccine (PCV-13) at any CD4 count and at least 1 y after receipt of the 23-valent pneumococcal polysaccharide vaccine (PPV). PPV is known to lead to hyporesponsiveness to subsequent pneumococcal vaccines for at least 1 y Whether PCV-13 would be more immunogenic if administered later after PPV receipt or at higher CD4 counts has not been tested.

METHODS

We prospectively collected serum from 96 HIV-infected adults before and after PCV-13 receipt, and measured antibody concentrations against 4 pneumococcal serotypes (3, 6A, 7F, and 19A) via indirect ELISA according to the WHO protocol. Post-booster antibody concentrations and fold-rise in antibody concentrations were compared according to time from PPV receipt and baseline CD4 count using univariate and multivariate analyses.

RESULTS

PPV receipt >3 versus 1-3 y prior did not significantly change post-vaccination antibody concentrations, but was associated with slightly higher fold-rise in antibody concentration for the 3 tested serotypes included in PPV, though this only reached significance for serotype 7F. CD4 count was significantly associated with post-vaccination antibody concentrations for 3 of 4 serotypes, but not for fold-rise in antibody concentration for any serotype.

CONCLUSION

Waiting longer than 1 y after PPV receipt to administer PCV-13 may slightly improve the antibody response to serotypes included in both vaccines. While higher CD4 count at PCV-13 administration results in higher post-vaccination antibody concentrations, this is likely because higher CD4 count is also associated with higher pre-vaccination antibody concentrations.

Quantitative and Functional Antibody Responses to the 13-Valent Conjugate and/or 23-Valent Purified Polysaccharide Vaccine in Aging HIV-Infected Adults

BACKGROUND

The number of aging human immunodeficiency virus-infected (HIV+) individuals living in the United States has substantially grown over the past two decades. Advanced age and HIV infection both increase susceptibility to Streptococcus pneumoniae infection due to B cell dysfunction. The combined impact of these factors on pneumococcal vaccine responses remains unknown.

METHODS

We assessed serum immunoglobulin (Ig) G and IgM levels and opsonophagocytic killing assay (OPA) titers to pneumococcal serotypes 14 and 23F in HIV+ subjects and HIV-uninfected (HIV-) controls 50-65 years old. HIV+ individuals with CD4⁺ T cells/μl (CD4) >200 and ≥1 year of antiretroviral therapy (ART) received either a dose of the 13-valent pneumococcal conjugate vaccine followed by the 23-valent pneumococcal polysaccharide vaccine 8 weeks later (PCV/PPV) as currently recommended (n=15) or a single dose of PPV only (n=22). HIV- controls received PCV/PPV (n=14).

RESULTS

HIV+ PCV/PPV and PPV groups exhibited similar increases in IgG levels and OPA titers for both serotypes after immunization. Postvaccination IgM levels for serotype 23F, but not 14, were significantly higher in HIV+ PCV/PPV compared to PPV groups. IgG and IgM levels for serotype 14 and OPA titers to serotype 23F were significantly reduced in HIV+ compared to HIV- PCV/PPV groups. Serotype-specific IgG levels correlated with OPA titers for all groups.

CONCLUSIONS

Our data suggest that the recommended PCV/PPV regimen may not significantly improve quantitative or functional antibody responses compared to PPV only in aging HIV+ subjects. Continued efforts aimed at improving vaccine responses in this high risk population are warranted.

Pneumococcal vaccination among HIV-infected adult patients in the era of combination antiretroviral therapy

HIV-infected patients remain at higher risk for pneumococcal disease than the general population despite immune reconstitution and suppression of HIV replication with combination antiretroviral therapy. Vaccination with 23-valent pneumococcal polysaccharide vaccine (PPV23) composed of T-cell-independent antigens has been recommended to reduce the risk of pneumococcal disease in HIV-infected adults. However, given the heterogeneity of study design, execution and subjects enrolled, studies examining serological responses to PPV23 yielded conflicting results and observational studies of clinical effectiveness only provided moderate evidence to support the routine use of PPV23 in HIV-infected adults. Pneumococcal conjugate vaccine (PCV), with conjugation of the capsular polysaccharide to a protein carrier, is more immunogenic than PPV23 and has been demonstrated to protect against pneumococcal disease in HIV-infected children and recurrent invasive pneumococcal disease in HIV-infected adolescents and adults. Guidelines have recently been revised to recommend that HIV-infected patients aged 19 y or older receive one dose of 13-valent pneumococcal conjugate vaccine (PCV13) followed by a booster vaccination with PPV23. In this paper, we review the studies using different vaccination strategies to improve immunogenicity among HIV-infected adult patients.

Recurrent severe invasive pneumococcal disease in an adult with previously unknown hyposplenia

BACKGROUND

The risk of life-threatening and invasive infections with encapsulated bacteria is increased in patients with hyposplenia or asplenia. We report a case of recurrent invasive pneumococcal meningitis in a woman with previous unknown hyposplenia. She was vaccinated after the first episode of meningitis and developed sufficient levels of pneumococcal antibodies. The pneumococcal strains isolated were serotype 7 F and 17 F. To our knowledge, there has been no previously reported case of recurrent invasive pneumococcal disease in a pneumococcal vaccinated adult with hyposplenia and apparently sufficient antibody response.

CASE PRESENTATION

We report the course of a 38-year-old Caucasian woman presenting with recurrent episodes of invasive pneumococcal disease (IPD) and previously unknown hyposplenia. Hyposplenia was discovered during the second episode of IPD and no underlying medical condition was found. Despite immunization against S. pneumoniae and measurement of what was interpreted as protective levels of serotype-specific IgG antibodies after vaccination, the patient suffered from a third episode of IPD.

CONCLUSIONS

Individuals with predisposing medical conditions or a history of severe infections with encapsulated bacteria should be screened for spleen dysfunction. If splenic function is impaired, prevention against severe invasive infection with encapsulated bacteria are a major priority.

Bacterial Infections in Adult HIV-Infected Patients

PURPOSE

The purpose of this article is to critically review articles published from the pre-HAART era to the present on bacterial infections in adult HIV-infected patients.

METHOD

Literature search on bacterial infections in HIV-infected patients yields predominantly small case series from single centers, many of which are retrospectively collected.

RESULTS

Variations in case selection limit the utility of these articles for assessing the epidemiology and clinical features of a particular infection. Nonetheless, numerous articles indicate that certain bacterial infections occur most often when CD4 cell counts are < 200/mm3. In the pre-HAART era, others suggest that PcP prophylaxis with TMP/SMX and MAC prophylaxis with macrolides reduced rates of several bacterial infections. Since the advent of HAART, however, some articles suggest that the incidence of various infections has declined and that withdrawal of OI prophylaxis in patients who have had HAART restoration of CD4 cell counts has not led to an increase in certain bacterial infections.

CONCLUSION

This review suggests that bacterial infections may have declined in the HAART era, as multicenter cohort studies have shown to be the case with AIDS-associated OIs. Nonetheless, preventive measures such as pneumococcal vaccination and smoking cessation remain effective strategies.

Vaccination in HIV-infected adults

Vaccines are critical components for protecting HIV-infected adults from an increasing number of preventable diseases. However, missed opportunities for vaccination among HIV-infected persons persist, likely due to concerns regarding the safety and efficacy of vaccines, as well as the changing nature of vaccine guidelines. In addition, the optimal timing of vaccination among HIV-infected adults in regards to HIV stage and receipt of antiretroviral therapy remain important questions. This article provides a review of the current recommendations regarding vaccines among HIV-infected adults and a comprehensive summary of the evidence-based literature of the benefits and risks of vaccines among this vulnerable population.

Revaccination with 7-valent pneumococcal conjugate vaccine elicits better serologic response than 23-valent pneumococcal polysaccharide vaccine in HIV-infected adult patients who have undergone primary vaccination with 23-valent pneumococcal polysaccharide vaccine in the era of combination antiretroviral therapy

HIV-infected adults who had received 23-valent pneumococcal polysaccharide vaccine (PPV23) five years or more earlier consecutively underwent revaccination with one dose of PPV23 (127 subjects) from December 2005 through October 2007, or upon change in standard of care, non-randomly one (50) or two doses (44) of 7-valent pneumococcal conjugate vaccine (PCV7) from October 2008 through June 2010. Serologic response was defined as ≥ 2-fold increase in the IgG level plus a level ≥ 1000ng/ml 48 weeks following revaccination. At week 48, the response rate was significantly higher in the 2-dose PCV7 group compared with that in the 1-dose PCV7 or PPV23 group (63.6% vs 32.0% vs 8.7%, respectively; P<0.05). Revaccination with one dose of PCV7 (AOR, 4.57), two doses of PCV7 (AOR, 22.66), and CD4 >350 cells/μl (AOR, 3.24) and undetectable viral load (AOR, 3.87) at revaccination were statistically significantly associated with a better serologic response at week 48. Despite the limitation that study arms were neither randomized nor contemporaneous, we conclude that revaccination with PCV7 appears to elicit a better serologic response than PPV23 in the HIV-infected adults who have received PPV23 five years or more earlier (clinical trial registration number: NCT00885625).

Long-term immune responses to vaccination in HIV-infected patients: a systematic review and meta-analysis

Vaccine-induced antibodies may wane more quickly in persons living with human immunodeficiency virus (HIV) than in healthy individuals. We reviewed the literature on vaccines routinely recommended in HIV-infected patients to estimate how seroprotection decreases over time in those who initially responded to immunization. For each study retrieved from the literature, the decrease of seroprotection was modeled with a log binomial generalized linear model, and data were pooled in a meta-analysis to provide estimates of seroprotection 2 and 5 years after the last vaccine administration. Our analyses confirmed that the duration of seroprotection was shorter in HIV-infected patients and that with current guidelines, a substantial proportion of patients would have lost protective antibodies before a booster was proposed. We therefore discuss the implications for the monitoring of antibody levels and timing of revaccination in these patients.

Pneumococcal immunization in immunocompromised hosts: where do we stand?

Immunocompromised patients are all at risk of invasive pneumococcal disease, of different degrees and timings. However, considerable progress in pneumococcal immunization over the last 30 years should benefit these patients. The 23-valent polysaccharide vaccine has been widely evaluated in these populations, but due to its low immunogenicity, its efficacy is sub-optimal, or even low. The principle of the conjugate vaccine is that, through the protein conjugation with the polysaccharide, the vaccine becomes more immunogenic, T-cell dependent, and thus providing a better early response and a boost effect. The 7-valent conjugate vaccine has been the first one to be evaluated in different immunocompromised populations. We review here the efficacy and safety of the different antipneumococcal vaccines in cancer, transplant and HIV-positive patients and propose a critical appraisal of the current guidelines.

Clostridium difficile in a HIV-infected cohort: incidence, risk factors, and clinical outcomes

OBJECTIVE

Clostridium difficile is the most commonly reported infectious diarrhoea in HIV-infected patients in the United States. We set out to determine the incidence, risk factors and clinical presentation of C. difficile infections (CDIs) in a cohort of HIV-infected individuals.

DESIGN

We performed a nested, case-control analysis with four non-CDI controls randomly selected for each case.

METHODS

We assessed the incidence of CDI in the Johns Hopkins HIV Clinical Cohort between 1 July 2003 and 31 December 2010. Incident cases were defined as first positive C. difficile cytotoxin assay or PCR for toxin B gene. We used conditional logistic regression models to assess risk factors for CDI. We abstracted data on the clinical presentation and outcomes from case chart review.

RESULTS

We identified 154 incident CDI cases for an incidence of 8.3 cases per 1000 patient years. No unique clinical features of HIV-associated CDI were identified. In multivariate analysis, risk of CDI was independently increased for CD4 cell count of 50 cells/μl or less [adjusted odds ratio (AOR) 20.7, 95% confidence interval (CI) 2.8-151.4], hospital onset CDI (AOR 26.7, 95% CI 3.1-231.2) and use of clindamycin (AOR 27.6, 95% CI 2.2-339.4), fluoroquinolones (AOR 4.5, 95% CI 1.2-17.5), macrolides (AOR 6.3, 95% CI 1.8-22.1), gastric acid suppressants (AOR 3.1, 95% CI 1.4-6.9) or immunosuppressive agents (AOR 6.8, 95% CI 1.2-39.6).

CONCLUSION

The incidence of CDI in HIV-infected patients was twice that previously reported. Our data show that compromised cellular immunity, as defined by CD4 cell count of 50 cells/μl or less, is a risk factor for CDI. Clinicians should be aware of the increased CDI risk, particularly in those with severe CD4 cell count suppression.

Serologic response to primary vaccination with 7-valent pneumococcal conjugate vaccine is better than with 23-valent pneumococcal polysaccharide vaccine in HIV-infected patients in the era of combination antiretroviral therapy

OBJECTIVES

The objectives of this study were to compare the serologic responses at week 48 to primary vaccination with 23-valent pneumococcal polysaccharide vaccine (PPV) vs. 7-valent pneumococcal conjugate vaccine (PCV); and to identify factors associated with serologic response in HIV-infected adult patients with access to combination antiretroviral therapy (cART).

METHODS

One hundred and four CD4-matched pairs of HIV-infected patients who underwent primary pneumococcal vaccination with 23-valent PPV or 7-valent PCV were enrolled for determinations of anti-capsular antibody responses against four serotypes (6B, 14, 19F and 23F) at baseline, 24 weeks and 48 weeks following vaccination. Significant antibody responses were defined as 2-fold or greater increase of antibody levels at week 48 compared with baseline. The logistic regression model was used to determine the factors associated with serologic response to at least one and two serotypes.

RESULTS

At week 48, patients who received PCV demonstrated a statistically significantly higher response rate to at least 2 serotypes than those who received PPV (37.5% vs. 20.2%, p = 0.006). In multivariate analysis, factors associated with significant antibody responses to at least one or two serotypes included receipt of PCV (adjusted odds ratio [AOR], 2.42 [95% CI, 1.23-4.78] and 3.58 [95% CI. 1.76-7.28], respectively), and undetectable plasma HIV RNA load (< 400 copies/ml) at vaccination (AOR, 1.47 [95% CI, 0.60-3.64] and 3.62 [95% CI, 1.11-11.81], respectively).

CONCLUSIONS

Primary vaccination with 7-valent PCV achieved a significantly better serologic responses to one or two out of the four serotypes studied at week 48 than with 23-valent PPV in HIV-infected patients in the cART era. Suppression of HIV replication when primary vaccination was administered was associated with better serologic responses.

Comparison of serologic responses to vaccination with one dose or two doses of 7-valent pneumococcal conjugate vaccine in HIV-infected adult patients

BACKGROUND

Vaccination with 7-valent pneumococcal conjugate vaccine (PCV) has been shown to decrease the incidence of recurrent invasive pneumococcal disease among HIV-infected adults in Africa. Longitudinal follow-up studies of serologic responses to different doses of 7-valent PCV are rarely performed in HIV-infected adult patients receiving combination antiretroviral therapy (cART).

METHODS

From October 2008 to June 2010, 115 CD4-matched pairs of HIV-infected patients aged ≥ 20 years who had no prior pneumococcal vaccination received one or two doses of 7-valent PCV. Anticapsular antibodies against 4 serotypes (6B, 14, 19F, and 23F) were examined at the 12th, 24th, 36th, and 48th week following vaccination. Significant antibody responses were defined as ≥ 2-fold increase in the IgG level plus a post-vaccination antibody level ≥ 1000 ng/ml.

RESULTS

The most common reported adverse effects were injection site soreness (19.3%) and pain (4.8%). Significant antibody response rate was highest for serotype 14, followed by 23F, 19F, and 6B in all of the four time points examined. At week 48, patients who received two doses of 7-valent PCV had a significantly higher response rate to serotype 6B (P=0.03) and 23F (P=0.01) than those who received one dose; moreover, the former group also had a higher response rate to at least one (P=0.03) and two serotypes (P=0.02) in intention-to-treat analysis than the latter group.

CONCLUSIONS

HIV-infected adult patients on cART who received two doses of 7-valent PCV achieved better serological responses to at least one serotype than those who received one dose during the 48 weeks of follow-up.

Safety, immunogenicity and efficacy of pneumococcal conjugate vaccine in HIV-infected individuals

Streptococcus pneumoniae is the leading bacterial opportunistic infection in HIV-infected individuals. Anti-retroviral treatment (ART) of HIV-infected individuals reduces their risk of invasive pneumococcal disease (IPD), however, it remains 20- to 40-fold greater compared with age-matched general population. This review summarizes the available published data on the immunogenicity, safety and efficacy of pneumococcal polysaccharide-protein conjugate vaccines (PCV) in HIV-infected children and adults.   Several studies have demonstrated that PCV are safe in the HIV-infected persons. Although PCV are immunogenic in HIV-infected infants, the antibodies produced are functionally impaired, there is possibly a lack or loss of anamnestic responses and immunity declines in later life However, quantitative and qualitative antibody responses to PCV in HIV-infected infants are enhanced when vaccination occurs whilst on ART, as well as if vaccination occurs when the CD4+ cell percentage is ≥ 25% and if the nadir CD4+ is > 15%. Although the efficacy of PCV was lower, the vaccine preventable burden of hospitalization for IPD and clinical pneumonia were 18-fold and 9-fold greater, respectively, in HIV-infected children compared with -uninfected children. In HIV-infected adults, PCV vaccination induces more durable and functional antibody responses in individuals on ART at the time of vaccination than in ART-naive adults, independently of baseline CD4+ cell count, although there does not appear to be much benefit from a second-dose of PCV. PCV has also been shown to reduce the risk of recurrent IPD by 74% in HIV-infected adults not on ART, albeit, also with subsequent decline in immunity and protection.

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.

A randomized clinical trial comparing revaccination with pneumococcal conjugate vaccine to polysaccharide vaccine among HIV-infected adults

BACKGROUND

The risk of pneumococcal disease persists, and antibody responses to revaccination with the 23-valent polysaccharide vaccine (PPV) are low among human immunodeficiency virus (HIV)-infected adults. We determined whether revaccination with the 7-valent pneumococcal conjugate vaccine (PCV) would enhance these responses.

METHODS

In a randomized clinical trial, we compared the immunogenicity of revaccination with PCV ( n = 131) or PPV (n = 73) among HIV-infected adults (median CD4 cell count, 533 cells/mm(3)) who had been vaccinated with PPV 3-8 years earlier. HIV-uninfected adults (n = 25) without prior pneumococcal vaccination received 1 dose of PCV. A positive response was defined as a >or=2-fold increase (from baseline to day 60) in capsule-specific immunoglobulin G, with a postvaccination level >or=1000 ng/mL for at least 2 of the 4 serotypes.

RESULTS

HIV-infected persons demonstrated a higher frequency of positive antibody responses to PCV than to PPV (57% vs 36%) (P = .004) and greater mean changes in the immunoglobulin G concentration from baseline to day 60 for serotypes 4, 9V, and 19F (P < .05, for all), but not for serotype 14. However, by day 180, both outcomes were similar. Responses to PCV were greater in frequency and magnitude for all serotypes in HIV-uninfected adults, compared with those in HIV-infected adults.

CONCLUSIONS

Among persons with HIV infection, revaccination with PCV was only transiently more immunogenic than PPV, and responses were inferior to those in HIV-uninfected subjects with primary vaccination. Pneumococcal vaccines with more robust and sustained immunogenicity are needed for HIV-infected adults. Clinical trial registration. ClinicalTrials.gov identifier NCT00622843.

Prevention of invasive pneumococcal disease among HIV-infected adults in the era of childhood pneumococcal immunization

OBJECTIVE

Human immunodeficiency virus (HIV) infection and AIDS increase the risk of invasive pneumococcal disease (IPD). We evaluated IPD among HIV-infected adults over a 10-year period in the US to identify opportunities for prevention of IPD among HIV-infected adults.

DESIGN

IPD and HIV surveillance in seven population-based and laboratory-based Active Bacterial Core surveillance areas.

METHODS

IPD cases were adults 18-64 years old with pneumococcus isolated from a normally sterile site during 1998-2007. Isolates were serotyped using the Quellung reaction. HIV/AIDS status was determined by medical record review. We calculated incidence of IPD among adults with AIDS using national case-based surveillance data.

RESULTS

Of 13 812 IPD cases among 18-64-year-olds, 3236 (23%) occurred among HIV-infected adults (with or without AIDS) and 1313 (10%) occurred among the subset of HIV-infected adults with AIDS. Compared with the period (1998-1999) before childhood 7-valent pneumococcal conjugate vaccine (PCV7) introduction in the US, the overall incidence of IPD among adults with AIDS decreased 25% from 399 to 298 cases per 100 000 by 2007 (P = 0.008). In 2006-2007, 8, 39 and 55% of IPD cases among adults with AIDS were caused by serotypes included in the 7-valent PCV, 13-valent PCV and 23-valent pneumococcal polysaccharide vaccines, respectively.

CONCLUSION

Sustained declines in IPD have occurred among adults with AIDS in the US, but incidence remained high 7 years after PCV7 introduction. More aggressive efforts, including HIV-prevention measures and the use of new PCVs in children and possibly HIV-infected adults, are necessary to further reduce IPD among HIV-infected adults.

Conjugate and polysaccharide pneumococcal vaccines do not improve initial response of the polysaccharide vaccine in HIV-infected adults

This is a randomized trial to compare the immunoglobulin G response and the antibody avidity after two pneumococcal vaccinations, conjugated pneumococcal vaccine (CPV) and polysaccharide pneumococcal vaccine (PPV) 4 weeks after vs. PPV alone in 202 HIV-infected adults. There were no differences in the two strategies, either in the percentage of immunoglobulin G two-fold increase for the CPV included serotypes or immunoglobulin G two-fold increase, reaching the level of 1 microg/ml except for serotype 23F (26% responded after conjugated pneumococcal vaccine + PPV vs. 14% after PPV). No avidity increases were seen in any strategy.

Evidence of early B-cell dysregulation in simian immunodeficiency virus infection: rapid depletion of naïve and memory B-cell subsets with delayed reconstitution of the naïve B-cell population

Despite eliciting a robust antibody response in humans, several studies in human immunodeficiency virus (HIV)-infected patients have demonstrated the presence of B-cell deficiencies during the chronic stage of infection. While several explanations for the HIV-induced B-cell deficit have been proposed, a clear mechanistic understanding of this loss of B-cell functionality is not known. This study utilizes simian immunodeficiency virus (SIV) infection of rhesus macaques to assess B-cell population dynamics beginning at the acute phase and continuing through the chronic phase of infection. Flow cytometric assessment demonstrated a significant early depletion of both naïve and memory B-cell subsets in the peripheral blood, with differential kinetics for recovery of these populations. Furthermore, the altered numbers of naïve and memory B-cell subsets in these animals corresponded with increased B-cell activation and altered proliferation profiles during the acute phase of infection. Finally, all animals produced high titers of antibody, demonstrating that the measurement of virus-specific antibody responses was not an accurate reflection of alterations in the B-cell compartment. These data indicate that dynamic B-cell population changes in SIV-infected macaques arise very early after infection at the precise time when an effective adaptive immune response is needed.

A 5-year longitudinal follow-up study of serological responses to 23-valent pneumococcal polysaccharide vaccination among patients with HIV infection who received highly active antiretroviral therapy

BACKGROUND

Long-term antibody responses to 23-valent pneumococcal polysaccharide vaccine (PPV) among HIV-infected patients receiving highly active antiretroviral therapy (HAART) are rarely investigated.

METHODS

Antibody responses to three pneumococcal capsular polysaccharides [Pneumococcal polysaccharide (PPS) 14, 19F and 23F] were assessed among 169 HIV-infected patients who received HAART and 23-valent PPV. Patients were stratified into four groups according to CD4 count at vaccination: group 1, CD4<100 cells/microL (n=35); group 2, CD4 100-199 cells/microL (n=36); group 3, CD4 200-349 cells/microL (n=34); and group 4, CD4>or=350 cells/microL (n=64). The proportion of patients who achieved increases in antibody titres of twofold or greater from baseline values (responders) was compared among the four groups of patients for five consecutive years after vaccination.

RESULTS

The proportion of responders to the three serotypes was significantly lower among patients in group 1 compared with those in the other three groups during yearly follow-up. Much faster loss of antibody responses was observed in group 1, although the rate of decline varied with the serotypes studied in the four groups. Compared with the nonresponders, more responders had CD4 counts >100 cells/microL at vaccination and achieved better virological suppression throughout the 5-year period, while the absolute increases of CD4 cell counts after HAART were not statistically significantly different.

CONCLUSIONS

Despite continued increases in CD4 cell counts after HAART, the proportion of HIV-infected patients who maintained antibody responses to PPV declined significantly over the 5-year follow-up period, especially among those who had CD4 counts <100 cells/microL at vaccination and who failed to achieve virological suppression.

A new endpoint definition improved clinical relevance and statistical power in a vaccine trial

OBJECTIVE

Endpoints used for the evaluation of immunogenicity in vaccine trials are often the proportion of individuals with immune response or geometric means of antibody concentrations for each serotype. When a vaccine includes several types of the same species, we illustrate how an endpoint combining all responses may improve clinical relevance and statistical power.

STUDY DESIGN AND SETTINGS

The motivating example was the ANRS 114 Pneumovac trial where the effect of two vaccine strategies against Streptococcus pneumoniae was assessed in adults infected by the Human Immunodeficiency Virus. The power associated with several endpoints was calculated in the example and in simulations. A new endpoint based on four ordered levels is formulated and analyzed by using a proportional odds model.

RESULTS AND CONCLUSION

The analysis of this new endpoint led to an odds ratio allowing detection of improvement and detriment. In the simulation study, this endpoint was associated with the largest statistical power by increasing the amount of information used as compared with usual endpoints. We recommend this new endpoint formulation in the formal development of a new vaccination regimen, whenever applicable.

The effect of 23-valent pneumococcal polysaccharide vaccine on immunological priming induced by 7-valent conjugate vaccine in asplenic subjects with beta-thalassemia

The effect of the 23-valent pneumococcal polysaccharide vaccine (PPV) on the 7-valent conjugate (PCV) vaccine-induced priming was evaluated in 35 splenectomised beta-thalassemics [median (range) age: 30 (12-41) years] vaccinated with either PCV/PPV or two PCVs 1 month apart, followed by a PPV booster 12 months later. 28/35 had already received 1-3 PPVs in the past. Different schedules induced similar anamnestic responses; however priming for 3/5 serotypes induced by one or two PCVs, was inferior in subjects who had received > or =2 PPVs in the past when compared with 23 aged-matched PPV-naïve beta-thalassemics. One PPV following PCV does not affect PCV priming; multiple PPVs induce hyporesponsiveness for some serotypes in splenectomised subjects with beta-thalassemia.

Initial and subsequent response to pneumococcal polysaccharide and protein-conjugate vaccines administered sequentially to adults who have recovered from pneumococcal pneumonia

BACKGROUND

Controversy persists over the benefits of pneumococcal polysaccharide vaccine (PPV) for adults at high risk for pneumococcal disease. We studied PPV, protein-conjugate pneumococcal vaccine (PCV), and immunologic "priming" with PCV followed by "boosting" with PPV in adults who had recovered from pneumococcal pneumonia.

METHODS

Subjects received PPV followed by PCV 6 months later, or vice versa. The levels of IgG to capsular polysaccharide and opsonophagocytic killing activity (OPK) were studied at baseline and at 4-8 weeks and 6 months after each vaccination.

RESULTS

PPV and PCV stimulated similar IgG levels and OPK at 4-8 weeks after vaccination. Six months after receipt of PPV, the antibody levels declined to baseline but remained modestly elevated after receipt of PCV. PCV administered 6 months after PPV stimulated modest increases in IgG level that failed to reach the peaks observed after receipt of PPV. In contrast, PPV administered 6 months after PCV caused dramatic increases in the levels of IgG and OPK for all polysaccharides at 4-8 weeks, consistent with a booster effect. Six months after receipt of the second vaccination, however, levels of IgG and OPK fell precipitously in all patients, approaching baseline levels.

CONCLUSIONS

In these high-risk subjects who have recovered after treatment for pneumonia, the effect of PPV is short-lived; PCV stimulates a more prolonged response. The use of PPV as a booster following PCV causes early increases in antibody levels, but the level of IgG declines rapidly thereafter, consistent with induction of suppressor cells or tolerance. Protein vaccines may be needed for high-risk adults.

Cross-sectional study of nasopharyngeal carriage of Streptococcus pneumoniae in human immunodeficiency virus-infected adults in the conjugate vaccine era

Human immunodeficiency virus (HIV)-infected patients have an increased rate of pneumococcal infections. Within the HIV-infected population, patients with low CD4(+) cell counts have a higher rate of pneumococcal infection. The purpose of our study was to determine pneumococcal carriage and to examine the serotypes carried by HIV-infected patients after the introduction of the conjugate vaccine. Nasopharyngeal swabs were obtained from patients during routine clinic visits. Samples were cultured on blood agar plates with gentamicin and screened for alpha-hemolysis, optochin sensitivity, and bile solubility. Capsular serotypes were determined by multiplex PCR, multibead assay, or latex agglutination. Antibiotic susceptibility was determined by the Etest method. Multilocus sequence typing was also performed. Of the 175 patients enrolled, 120 patients had absolute CD4(+) cell counts above 200/mm(3) and 55 had counts below 200/mm(3). A total of six (3.4%) patients carried pneumococci. All but one of these patients had received the 23-valent pneumococcal vaccine within the previous 5 years. Five of the isolates were serotypes that are not included in the 7-valent conjugate vaccine. Immunization with the pneumococcal polysaccharide vaccine does not prevent colonization in HIV-infected patients; however, the observation of carriage of serotypes not included in the conjugate vaccine may be due to herd immunity and serotype replacement effects in the general population.

Induction of opsonophagocytic killing activity with pneumococcal conjugate vaccine in human immunodeficiency virus-infected Ugandan adults

The levels of IgG determined by ELISA may have limited relevance in human immunodeficiency virus (HIV)-infected adults because of non-functional antibodies. 58 HIV-1-infected and 29 HIV-uninfected Ugandan adults were immunized with conjugate vaccine (CV) followed by polysaccharide vaccine (PV) after a 2-month interval, and the opsonophagocytic killing (OPK) titers against serotype 4 or 14 pneumococcal strains as well as the levels of serotype-specific IgG in sera were determined. Significant increases were found in the OPK titers and IgG levels for both serotypes after CV vaccination irrespective of HIV status. Increases in IgG levels and OPK titers were largely dependent on the CD4(+) cell counts, except for increases in the IgG levels for serotype 4. The proportions with serum OPK titer equal to or greater than 8 were 0-4.3% for serotype 4 and 26.7-42.9% for serotype 14 before vaccination, but the proportions increased up to 43.3-86.2% for serotype 4 and 63.3-96.6% for serotype 14 in all three groups 2 months after CV vaccination. The serum OPK titers remained at levels higher than the pre-vaccination level for at least 8 months after CV vaccination. A single dose of CV could afford some protective immunity in HIV-infected African adults before the introduction of antiretroviral therapy.

B cell immunopathology during HIV-1 infection: lessons to learn for HIV-1 vaccine design

Induction of broad HIV-1 neutralizing antibodies should be a major goal of an effective HIV-1 vaccine. However, B cells are severely damaged during HIV-1 infection with loss of memory B cells and decline of serological memory. The molecular events leading to B cell damage must be further characterized with the aim of selecting vaccine components allowing preservation of B cell functions. This review focuses on B cell damage and antibody responses in HIV-1-infected patients during vaccination studies with viral and bacterial antigens. In addition novel data indicate that B cell activation may be at the basis of impaired immune responses.

Immunological efficacy of a prime-boost pneumococcal vaccination in HIV-infected adults

OBJECTIVE

To evaluate whether a strategy combining a prime with a 7-valent conjugate pneumococcal vaccine (PCV) followed by a boost with the 23-valent polysaccharide vaccine (PPV) would improve immunogenicity against Streptococcus pneumoniae polysaccharides in HIV-infected patients.

DESIGN

Randomized controlled phase II trial.

METHODS

Two-hundred and twelve patients with CD4 cell counts of 200-500 cells/mul and HIV RNA< 4 log10 copies/ml, regardless of antiretroviral treatment, were randomized to receive either PCV at week 0 and PPV at week 4 (n = 106) or PPV alone at week 4 (n = 106). The proportion of responders to 0, 1-2, 3-4, 5-7 serotypes shared by the two vaccines was evaluated at week 8 and compared using a proportional odds model allowing for adjustment for CD4 cell count, HIV RNA and antiretroviral treatment.

RESULTS

At week 8, the profile of response was better in the prime-boost group compared to the PPV group, as determined by the frequency of patients who reached both a twofold increase of serotype-specific IgG levels and IgG level >/= 1 mug/ml [proportional odds ratio (OR), 2.09; 95% confidence interval (CI), 1.25-3.51; P = 0.005]. No differences in responders were found 4 weeks after PCV or PPV alone, suggesting that PCV primed for response to PPV. Early differences between groups remained significant at week 24 (proportional OR, 2.14; 95% CI, 1.30-3.54; P = 0.003).

CONCLUSIONS

In a setting of practical care, a PCV prime-PPV boost strategy enhances the frequency, breadth and magnitude of antibody responses against SPP in HIV-infected adults.

Pertussis booster vaccination in HIV-infected children receiving highly active antiretroviral therapy

OBJECTIVE

Our goal was to evaluate the immunogenicity and safety of pertussis booster vaccination in children infected with HIV on highly active antiretroviral therapy (HAART).

PATIENTS AND METHODS

HIV-infected children on stable HAART for > or = 3 months with plasma HIV-RNA concentrations of < 30,000 to 60,000 copies per mL who previously received > or = 4 doses of diphtheria-tetanus-pertussis (DTP)-containing vaccine were eligible. Diphtheria-tetanus-acellular pertussis (DTaP) vaccine was administered to subjects 2 to < 7 years old who had 4 previous DTP-containing vaccines, subjects 2 to < 7 years old who had > or = 5 previous DTP-containing vaccines and negative tetanus antibody, and subjects > or = 7 to < or = 13 years old who had negative tetanus antibody. Pertussis toxin and filamentous hemagglutinin antibodies were measured before and 8, 24, and 72 weeks after DTaP vaccine.

RESULTS

Ninety-two subjects received DTaP vaccine and met criteria for analysis. Antibody concentrations were low at entry: pertussis toxin geometric mean concentration at 4.8 enzyme-linked immunosorbent assay units (EU) per mL and filamentous hemagglutinin geometric mean concentration at 4.1 EU/mL. Pertussis toxin and filamentous hemagglutinin geometric mean concentrations rose to 22.3 and 77.0 EU/mL, respectively, 8 weeks after the study DTaP vaccine. Antibody concentrations fell by 24 weeks after vaccination but remained higher than before vaccination. Predictors of response 8 weeks after DTaP vaccine included the concentration of homologous antibody, lower HIV-RNA level, and higher CD4 percentage at entry. One vaccinated subject experienced erythema and induration of > or = 25 mm.

CONCLUSIONS

A DTaP vaccine booster was well tolerated by children on HAART and induced increases in antibodies. Antibody concentrations after vaccination were lower than those reported in populations uninfected by HIV. Although comparison among studies must be made with caution, these data suggest that children infected with HIV may be deficient in immunologic memory from previous DTP-containing vaccination and/or that immune reconstitution with HAART may be incomplete for pertussis antigens.

Immunogenicity of varying dosages of 7-valent pneumococcal polysaccharide-protein conjugate vaccine in seniors previously vaccinated with 23-valent pneumococcal polysaccharide vaccine

In this dose-ranging study 220 seniors who had received the 23-valent pneumococcal polysaccharide (PnPS) vaccine at least 5 years prior to enrollment were assigned to receive one of four volumes (0.1, 0.5, 1 or 2 ml) of 7-valent pneumococcal conjugate (PnC) vaccine or a 0.5 ml dose of 23-valent PnPS vaccine. All participants received a reduced challenge dose of 0.1 ml of PnPS vaccine 1 year after enrollment. There was evidence of a dose response to PnC vaccine and antibody levels in the 1 ml PnC group tended to be significantly higher than in the PnPS group. A booster response to the challenge vaccination was not observed. Administration of a 1 ml dose of PnC vaccine is more immunogenic than 0.5 ml of PnPS vaccine in elderly adults previously vaccinated with PnPS vaccine.

A human monoclonal immunoglobulin M reduces bacteremia and inflammation in a mouse model of systemic pneumococcal infection

Antibody-based approaches to pneumococcal disease may hold promise for immunocompromised patients in whom vaccines are less immunogenic and/or in the context of antimicrobial resistance. Antibody-mediated protection against experimental pneumococcal pneumonia has been shown to depend on immunoregulation, but the relationship between antibody and protection against pneumococcal sepsis and immunoregulation has not been examined. Similarly, the requirement for B and T cells for antibody efficacy is not known. In this study, we determined the efficacy of the human pneumococcal capsular polysaccharide serotype 3-specific antibody, A7 (immunoglobulin M [IgM]), in secretory IgM (sIgM)(-/-), CD4(-/-), CD8(-/-), muMT(-/-), and SCID mice and investigated its effect on cytokine and chemokine expression in sera and spleens from mice with intact cellular immunity. A7 is known to be protective against systemic infection with serotype 3 and to require complement for efficacy. Compared to that of an isotype control antibody, A7 administration prolonged the survival of mice of each immunodeficient strain and was associated with a significant reduction in CFU in blood, lung, and spleen samples and a significantly reduced level of keratinocyte-derived chemokine (KC), interleukin-6 (IL-6), and macrophage inflammatory protein-2 (MIP-2) expression in normal and sIgM(-/-) mice. Studies with mice treated with penicillin revealed similar reductions in CFU and similar levels of IL-6, KC, or MIP-2 expression in A7- and penicillin-treated mice. These findings demonstrate that natural IgM and B and T cells are dispensable for A7-mediated protection against experimental pneumococcal sepsis and suggest that the efficacy of antibody-mediated protection depends on immunomodulation. Taken together, our data extend the association between antibody-mediated protection and immunomodulation to protection against systemic pneumococcal infection and to a clinically important serotype often responsible for pneumococcal sepsis.

Immunogenicity, safety, and predictors of response after a pneumococcal conjugate and pneumococcal polysaccharide vaccine series in human immunodeficiency virus-infected children receiving highly active antiretroviral therapy

BACKGROUND

The immunogenicity and safety of 2 doses of pneumococcal conjugate vaccine (PCV) and 1 dose of pneumococcal polysaccharide vaccine (PPV) were evaluated in human immunodeficiency virus (HIV)-infected children receiving highly active antiretroviral therapy (HAART).

METHODS

Children 2 to <19 years, receiving stable HAART for > or =3-6 months, with HIV RNA PCR <30,000-60,000 copies/mL, received 2 doses of PCV and 1 dose of PPV at sequential 8-week intervals. Antibodies to pneumococcal serotypes (STs) 1 (PPV only) and 6B, 14, 19F, and 23F (PCV and PPV) were measured by ELISA.

RESULTS

Two hundred sixty-three subjects were enrolled, of whom 225 met criteria for inclusion in the primary dataset. Antibody concentrations were low at entry, despite previous PPV in 75%. After vaccination, 76%-96% had concentrations > or =0.5 microg/mL and 62-88% > or =1.0 microg/mL to the 5 STs (geometric mean concentrations [GMCs] = 1.44-4.25 microg/mL). Incremental gains in antibody concentration occurred with each vaccine dose. Predictors of response included higher antibody concentration at entry, higher immune stratum (based on nadir CD4% before HAART and CD4% at screening), lower entry viral RNA, longer duration of the entry HAART regimen, and age <7 years. Response was more consistently related to screening CD4% than nadir CD4%. Seven percent had vaccine-related grade 3 events, most of which were local reactions.

CONCLUSIONS

Two PCVs and 1 PPV were immunogenic and safe in HIV-infected children 2 to <19 years who were receiving HAART. Responses were suggestive of functional immune reconstitution. Immunologic status based on nadir and, especially, current CD4% and control of HIV viremia were independent determinants of response.

Vaccination in patients with HIV infection

Although vaccine-preventable diseases are common in HIV, concerns about vaccine safety and lack of efficacy in this patient population often lead to missed opportunities for vaccination. In this article, we review the literature regarding vaccine risks and benefits and offer recommendations regarding their use and timing in patients with HIV infection.

Vaccination of stem cell transplant recipients: recommendations of the Infectious Diseases Working Party of the EBMT

Over the last 25 years, the numbers of hematopoietic stem cell transplant (SCT) patients have increased rapidly. Infections have been major obstacles for successful transplantation. Thus, infection prevention is very important in transplant recipients. As the results of transplantation have improved, the number of long-term survivors has increased. Vaccination is a potentially important strategy for reducing the risk for vaccine-preventable infections after SCT. The EBMT produced recommendations for vaccination of SCT recipients published in Bone Marrow Transplantation in 1995. This paper updates the previous recommendations based on current knowledge.

Assessment of antibody response elicited by a 7-valent pneumococcal conjugate vaccine in pediatric human immunodeficiency virus infection

We investigated antibody responses against pneumococci of serotypes 6B, 14, and 23F in 56 children and adolescents with perinatal human immunodeficiency virus (HIV) infection who were vaccinated with 7-valent pneumococcal conjugate vaccine. Overall immune responses differed greatly between serotypes. Correlation coefficients between immunoglobulin G (IgG) measured by enzyme-linked immunosorbent assay (ELISA) and functional antibodies measured by a flow cytometry opsonophagocytosis assay (OPA) varied with serotype and time points studied. After 3 months of administering a second PCV7 dose we got the highest correlation (with significant r values of 0.754, 0.414, and 0.593 for serotypes 6B, 14, and 23F, respectively) but no significant increase in IgG concentration and OPA titers compared to the first dose. We defined a responder to a serotype included in the vaccine with two criteria: frequency of at least twofold OPA and ELISA increases for each serotype and frequency of conversion from negative to positive OPA levels. Responders varied from 43.9% to 46.3%, 28.5% to 50.0%, and 38.0% to 50.0% for serotypes 6B, 14, and 23F, respectively, depending on the response criterion. The present research highlights the importance of demonstrating vaccine immunogenicity with suitable immunological endpoints in immunocompromised patients and also the need to define how much antibody is required for protection from different serotypes, since immunogenicity differed significantly between serotypes.

Pharmacotherapy, vaccines and malaria advice for HIV-infected travellers

Since the introduction of effective antiretroviral therapy (ART), HIV-infected individuals are travelling more frequently and international travel has become much safer. Specific concerns include the safety of ART during travel, drug adherence and interaction considerations, and effects of immunosuppression. This review describes potentially important infections, vaccine effectiveness, safety and special approaches for their use, and HIV-related issues regarding predeparture counselling. With advanced immunosuppression (CD4+ T-cell count < 200/microl or < 14%), the immunogenicity of several vaccines is reduced, complications could occur after live attenuated vaccines and certain infections acquired during travel may be more frequent or severe. Challenges include the best options for malaria chemoprophylaxis, standby treatment and medical follow-up of the increasing number of HIV-infected long-term travellers.

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.

Pneumococcal conjugate vaccines—a European perspective

Streptococcus pneumoniae is a leading cause of bacterial pneumonia, meningitis, and acute otitis media in children and adults worldwide. In the age group of < 2 years the incidence of invasive pneumococcal disease ranges from approximately 14 cases per 100,000 in Germany and the Netherlands and more than 90 per 100,000 children in Spain. The vulnerability of children to S. pneumoniae can also be demonstrated by the high rate of sequelae (> 20% in Germany) and the high mortality (7.5%) in pneumococcal meningitis. Furthermore, antibiotic resistance of S. pneumoniae is increasing in Europe, particularly in France, Spain, and Eastern European countries, whereas Germany and Northern Europe are only marginally affected. A 7-valent pneumococcal conjugate vaccine (7vPCV) that was shown to be highly efficacious in preventing invasive pneumococcal disease in infants in the USA was licensed in Europe in 2001. It is expected that broad usage of the vaccine would reduce the incidence of invasive pneumococcal disease and the levels of pneumococcal resistance significantly. Important questions have been raised regarding the effectiveness of this vaccine in high-risk populations, serotype replacement, the efficacy of this vaccine in otitis media, and the co-administration of the new vaccine with other standard childhood vaccines used in various European countries. France and Spain currently have the most-wide ranging guidelines recommending pneumococcal vaccination for children. Overall, the development of pneumococcal conjugate vaccines is a significant step in the control of pneumococcal disease in children in Europe. Further progress in pneumococcal vaccine development can be expected from conjugate vaccines including more than seven serotypes (9-valent, 11-valent).

Global strategies to prevent bacterial pneumonia in adults with HIV disease

We examined the peer-reviewed literature on the burden of bacterial pneumonia and the effectiveness of interventions for its prevention among HIV-infected adults in developed and developing countries. Bacterial pneumonia rates were up to 25-fold higher among HIV-infected adults than in the general community, with rates increasing as CD4+ T-cell count decreases. In developed countries, cohort studies showed that highly active antiretroviral therapy (HAART) had the most consistent effect on reducing pneumonia. In a prospective cohort and case-control studies from these regions, pneumococcal polysaccharide vaccine reduced pneumococcal disease in certain subgroups, particularly those with higher CD4+ T cells/microL. In patients with fewer than 200 CD4+ T cells/microL, antimicrobial prophylaxis was usually effective in reducing pneumonia. In sub-Saharan Africa, randomised controlled trials concluded that co-trimoxazole prophylaxis decreased rates of bacterial pneumonia, but pneumococcal polysaccharide vaccine prevented neither pneumonia nor invasive pneumococcal disease. Although not yet fully evaluated in Africa, based on experience in industrialised nations, use of HAART in Africa may have substantial potential to prevent bacterial pneumonia.

Review of pneumococcal conjugate vaccine in adults: implications on clinical development

A literature review was conducted to determine if pneumococcal conjugate vaccines administered to healthy and immunocompromised adults, in comparison with the known efficacy in children, showed immunogenicity. Fifteen publications were retrieved. Clinical studies had been conducted using vaccines from different manufacturers, in different populations, using varied methodologies. No clear evidence of the superiority of the conjugate vaccine over the currently licensed polysaccharide vaccine emerged. Possible reasons for the lack of superiority and its implications on vaccine development are discussed.

Economic aspects of pneumococcal pneumonia: a review of the literature

In this review, the economic aspects of pneumococcal pneumonia are analysed, including the costs, cost effectiveness and cost benefit of treatment and prevention. We identified eight cost-of-illness studies, 15 analyses comparing the costs of different treatment options and 15 economic evaluations of prevention that met our search criteria. The studies were conducted largely in Europe and the US. Most pertained to community-acquired pneumonia (CAP) in general, without specific analysis of pneumococcus-related illness. Many of the studies were considered to be of poor quality for the following reasons: comparison without randomisation or control variables, disregard of health outcomes, small sample size, restriction of costs to drug costs and vague or disputable sources of cost information. In the US, hospitalisation costs resulting from CAP can be estimated to be between US 7,000 dollars and US 8,000 dollars per admission or US 4 million dollars per 100,000 population. Hospitalisation costs are significant (representing about 90% of total costs), but are much lower in Europe than in the US (one-third to one-ninth of the US estimates in the UK and Spain, respectively). In general, economic studies of treatment for pneumococcal pneumonia are in line with clinical evidence. A drug with proven clinical effectiveness would also appear to be supported from an economic stand point. Furthermore, economic data support an early switch from an intravenous to an oral antibacterial, the use of quinolones for inpatients with CAP, and also the use of guidelines built on clinical evidence. Of all the possible preventive strategies for pneumococcal pneumonia, only vaccination has been subjected to economic evaluation. Pneumococcal polysaccharide vaccine seems relatively cost effective (and potentially cost saving) for those between 65 and 75 years of age, for military recruits and for HIV positive patients with a sufficiently high CD4 cell count. Evaluations of the pneumococcal conjugate vaccine (PCV) indicate the price of the vaccine to be the main determinant of cost effectiveness. As the current price is high (in the order of US 50 dollars per dose), the economic attractiveness of the universal PCV vaccination strategies hinges on the potential for price reductions and the willingness of decision makers to adopt a societal perspective.