The immunogenicity and safety of pneumococcal conjugate vaccine in human immunodeficiency virus-infected Thai children

Immunogenicity and safety of a hexavalent pediatric vaccine in HIV-exposed infected and uninfected infants in Republic of South Africa

Human immunodeficiency virus (HIV)-exposed infants may be at increased risk of vaccine-preventable disease. This study was conducted as a post-licensure commitment in this population to evaluate the primary series, antibody persistence, and booster response to a licensed fully liquid hexavalent vaccine containing diphtheria (D), tetanus (T), acellular pertussis (aP), inactivated poliovirus (IPV), hepatitis B (HB), and Haemophilus influenzae type b antigens (PRP~T). This was a Phase III, open-label, randomized study conducted at a single center in the Republic of South Africa. The DTaP-IPV-HB-PRP~T vaccine was administered to HIV-exposed infected (Group A: N = 14) and HIV-exposed uninfected (Group B: N = 50) infants as a 6, 10, 14 week primary series with a toddler booster at 15–18 months of age. Immunogenicity of each antigen was measured using validated assays and vaccine reactogenicity was recorded using diary cards. The low number of HIV-exposed infected participants, due to widespread pre- and peri-natal retroviral treatment, meant that between-group comparisons should be treated with caution. In each group, primary series and booster immune seroprotection rates were strong, and pre-booster antibody persistence was good, although anti-HBs ≥10 mIU/mL in Group A was 78.6% post-primary series, 58.3% pre-booster, and 75.0% post-booster. There were no safety concerns. In conclusion, primary series and booster vaccination of the DTaP-IPV-HB-PRP~T vaccine were immunogenic and safe in HIV-exposed infected and uninfected infants. These results were comparable to historical data in healthy infants and toddlers.

Nasopharyngeal Pneumococcal Colonization and Impact of a Single Dose of 13-Valent Pneumococcal Conjugate Vaccine in Indian Children With HIV and Their Unvaccinated Parents

BACKGROUND

Human immunodeficiency virus (HIV) infection increases risk of invasive disease from Streptococcus pneumoniae. Pneumococcal conjugate vaccines (PCV) prevent invasive disease and acquisition of vaccine type (VT) pneumococcus in the nasopharynx.

OBJECTIVE

To look at the safety and impact of one dose of PCV13 on acquisition of VT pneumococcal carriage in Indian children with HIV.

METHOD

We conducted a cohort study in families of HIV-infected children (CLH) and families of HIV-uninfected children (HUC) in West Bengal. All children received one dose of PCV13. Nasopharyngeal swabs were collected from children and parents at baseline and 2 months after vaccination.

RESULT

One hundred and fifteen CLH and 47 HUC received one dose of PCV13. Fifty-eight percent of CLH were on antiretroviral therapy (ART), and the median nadir CD4 count was 287. There were no significant adverse events in either group. HUC had more VT colonization than CLH-55% versus 23% of all pneumococcal isolates. HIV infection doubled the risk of nonvaccine serotype colonization (P = 0.03). There was no difference in acquisition of VT isolates in CLH (4.4%) and HUC (4.5%) post-PCV13; however, older CLH (>5 years) had decreased clearance of VT strains. ART made no difference in pneumococcal colonization at baseline or after PCV13; however, CLH with higher nadir CD4 counts before starting ART were less likely to have VT colonization post-PCV13 (prevalence ratio, 0.2; 95% confidence interval: 0.1-0.5).

CONCLUSION

While there was no difference in acquisition of VT nasopharyngeal carriage of pneumococcus in CLH and HUC after one dose of PCV13, earlier access to ART may impact response to PCV13 in CLH.

Pneumococcal conjugate vaccine in HIV-infected and HIV-exposed, uninfected children

INTRODUCTION

Incidence of invasive pneumococcal disease (IPD) among HIV-infected children is 20-40 fold greater compared to HIV-uninfected children, including among HIV-infected children on antiretroviral therapy (ART). Also, HIV-exposed, uninfected children have 2.7-fold greater risk of IPD compared to HIV-unexposed children. Areas covered: We reviewed studies identified on Pubmed database with the terms 'PCV' and 'HIV'; studies involving adults only were excluded. Expert commentary: While ART and pneumococcal conjugate vaccines (PCV) have reduced IPD morbidity and mortality in HIV-infected children, ART-naïve and immunosuppressed children have inferior immunogenicity to most PCV serotypes; highlighting the need for concomitant use of ART with PCV. Furthermore, studies to determine optimal PCV dosing schedules, timing and number of doses, are urgently required to ensure sustained vaccine efficacy in HIV-infected children.

Decline in Child Hospitalization and Mortality After the Introduction of the 7-Valent Pneumococcal Conjugative Vaccine in Rwanda

Pneumonia is a public health problem in the tropics, and the 7-valent pneumococcal conjugative vaccine (PCV-7) has been introduced in an effort to prevent the disease and therefore reduce childhood mortality. In Rwanda, PCV-7 was introduced in 2009, and we aimed to determine its impact on the rate of child hospitalization/mortality due to pneumonia. A retrospective survey was conducted on hospitalization rates and pediatric deaths between two periods, that is, before the introduction of PCV-7 (2007-2009) and after the introduction of PCV-7 (2010-2013) in Kabutare District Hospital. There was a 53% reduction in hospitalization, with a significant decline in in-hospital deaths between the two periods. There was also a significant correlation between vaccination coverage and decline in hospitalization rates between 2009 and 2013. We conclude that PCV-7 vaccine is associated with significant reduction in the rate of child hospitalization and mortality but more mechanistic studies are warranted to determine the immunological impact, especially in the context of coinfections and malnutrition.

B-cell development and pneumococcal immunity in vertically acquired HIV infection

OBJECTIVES

Many children with HIV infection now survive into adulthood. This study explored the impact of vertically acquired HIV in the era of antiretroviral therapy on the development of humoral immunity.

DESIGN

Natural and vaccine-related immunity to pneumococcus and B-cell phenotype was characterized and compared in three groups of young adults: those with vertically-acquired infection, those with horizontally acquired infection and healthy controls.

METHODS

Serotype-specific pneumococcal (Pnc) immunoglobulin M and G concentrations before and up to 1 year post-Pnc polysaccharide (Pneumovax) immunization were determined, and opsonophagocytic activity was analysed. B-cell subpopulations and dynamic markers of B-cell signalling, turnover and susceptibility to apoptosis were evaluated by flow cytometry.

RESULTS

HIV-infected patients showed impaired natural Pnc immunity and reduced humoral responses to immunization with Pneumovax; this was greatest in those viraemic at time of the study. Early-life viral control before the age of 10 years diminished these changes. Expanded populations of abnormally activated and immature B-cells were seen in both HIV-infected cohorts. Vertically infected patients were particularly vulnerable to reductions in marginal zone and switched memory populations. These aberrations were reduced in patients with early-life viral control.

CONCLUSION

In children with HIV, damage to B-cell memory populations and impaired natural and vaccine immunity to pneumococcus is evident in early adult life. Sustained viral control from early childhood may help to limit this effect and optimize humoral immunity in adult life.

Immunogenicity and Safety of the 13-Valent Pneumococcal Conjugate Vaccine versus the 23-Valent Polysaccharide Vaccine in Unvaccinated HIV-Infected Adults: A Pilot, Prospective Controlled Study

Objectives

Definition of the optimal pneumococcal vaccine strategy in HIV-infected adults is still under evaluation. We aimed to compare immunogenicity and safety of the 13-valent pneumococcal conjugate vaccine (PCV13) versus the 23-valent polysaccharide vaccine (PPSV23) in HIV-infected adults.

Methods

We performed a pilot, prospective controlled study enrolling HIV-infected pneumococcal vaccine-naïve outpatients, aged 18–65 years with CD4 counts ≥200 cells/μL. Eligible subjects were recruited into two parallel groups: group 1 (n = 50) received two doses of PCV13 eight weeks apart, and group 2 (n = 50) received one dose of PPSV23, as part of their standard of care. Anti-pneumococcal capsular polysaccharide immunoglobulin G concentrations were quantified by ELISA at baseline, 8, 24 and 48 weeks. Clinical and viro-immunological follow-up was performed at the same time points. Unvaccinated, age-matched HIV-negative adults (n = 100) were also enrolled as baseline controls.

Results

Pre-vaccination specific IgG titers for each pneumococcal antigen did not differ between study groups but they were constantly lower than those from the HIV-negative controls. After immunization, significant increases in IgG titers were observed in both study groups at each time point compared to baseline, but response to serotype 3 was blunted in group 1. Antibody titers for each antigen did not differ between study groups at week 48. Overall, the proportion of subjects achieving seroprotection and seroconversion to all serotypes was comparable between groups. A marked decrease in IgG levels over time was observed with both vaccines. No relevant adverse reactions were reported in either group.

Conclusions

In this population with favorable immune profile, no relevant differences were observed in immunogenicity between PCV13 and PPSV23. Both vaccines were safe and well tolerated.

Trial Registration

ClinicalTrials.gov NCT02123433

Impact of Pneumococcal Conjugate Vaccine Administration in Pediatric Older Age Groups in Low and Middle Income Countries: A Systematic Review

INTRODUCTION

Pneumococcal conjugate vaccine (PCV) is included in the World Health Organization's routine immunization schedule and is recommended by WHO for vaccination in high-risk children up to 60 months. However, many countries do not recommend vaccination in older age groups, nor have donors committed to supporting extended age group vaccination. To better inform decision-making, this systematic review examines the direct impact of extended age group vaccination in children over 12 months in low and middle income countries.

METHODS

An a priori protocol was used. Using pre-specified terms, a search was conducted using PubMed, LILACS, Cochrane Infectious Diseases Group Specialized Register, Cochrane Central Register of Controlled Trials, CAB Abstracts, clinicaltrials.gov and the International Symposium on Pneumococci and Pneumococcal Diseases abstracts. The primary outcome was disease incidence, with antibody titers and nasopharyngeal carriage included as secondary outcomes.

RESULTS

Eighteen studies reported on disease incidence, immune response, and nasopharyngeal carriage. PCV administered after 12 months of age led to significant declines in invasive pneumococcal disease. Immune response to vaccine type serotypes was significantly higher for those vaccinated at older ages than the unimmunized at the established 0.2 ug/ml and 0.35 ug/ml thresholds. Vaccination administered after one year of age significantly reduced VT carriage with odds ratios ranging from 0.213 to 0.69 over four years. A GRADE analysis indicated that the studies were of high quality.

DISCUSSION

PCV administration in children over 12 months leads to significant protection. The direct impact of PCV administration, coupled with the large cohort of children missed in first year vaccination, indicates that countries should initiate or expand PCV immunization for extended age group vaccinations. Donors should support implementation of PCV as part of delayed or interrupted immunization for older children. For countries to effectively implement extended age vaccinations, access to affordably-priced PCV is critical.

Long-term effect of highly active antiretroviral therapy on immunologic features in children

BACKGROUND

Highly active antiretroviral therapy (HAART) has transformed human immunodeficiency virus infection (HIV) into a chronic condition. The effects of long-term HAART on the immune system activity of early infected children are not fully understood. Hence, the aim of this review is to investigate immune system recovery and residual alteration in HIV-infected children receiving HAART in high-income countries.

METHODS

A systematic review was performed by searches of PubMed and references of the relevant articles. Studies published between January 1, 2000 and April 1, 2014 and conducted in high-income countries reporting data on immunological features in HIV-infected children receiving HAART were included in this review.

RESULTS

Fifty-three articles were included in this review. Present knowledge on B-cell and T-cell function, immunoglobulin production, response to vaccine and innate immune system activity in HIV-infected children receiving HAART is discussed.

CONCLUSION

Starting therapy as soon as diagnosis is ascertained and monitoring vaccine response in children under HAART are the most important tools to safeguard immunological function in HIV-infected children.

Serological response to 13-valent pneumococcal conjugate vaccine in children and adolescents with perinatally acquired HIV infection

Background:

Children with perinatally acquired HIV (paHIV) remain at an increased risk of pneumococcal infection despite highly active antiretroviral therapy (HAART). Beyond infancy, responses to pneumococcal conjugate vaccine (PCV) remain under-investigated. There are currently no published data on serological response to 13-valent PCV (PCV13) in the HIV-infected populations.

Methods:

We measured pneumococcal serotype-specific IgG in 48 paHIV-infected child patients (CP), 27 young adult healthy controls (AHC) and 30 child healthy controls (CHC). Opsonophagocytic assay (OPA) titres for three PCV13-exclusive serotypes were measured in a subset of children. Serotype-specific IgG was repeated 1 and 6 months following PCV13 vaccination of CP and AHC groups. OPA titres for four serotypes were measured at the 1-month time-point.

Results:

The majority of CP, CHC and AHC had serotype-specific IgG above 0.35 μg/ml at baseline, although OPA activity was undetectable for two of the three serotypes studied. Baseline IgG concentrations were significantly lower in CP than AHC for a proportion of serotypes and were strongly predictive of responses to vaccine. After adjusting for baseline, postvaccination IgG concentrations were comparable, although responses to some serotypes were impaired for CP. OPA correlated well with IgG after vaccination. Detectable HIV viral load was associated with significantly lower IgG concentration and OPA titre.

Conclusion:

Children with paHIV mount a robust serological response to PCV13 for most but not all vaccine serotypes. Viral load suppression with HAART and higher baseline IgG concentration are associated with higher postvaccination antibody levels. This has implications for HAART treatment and vaccination practices.

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.

Antibody persistence and immunologic memory after sequential pneumococcal conjugate and polysaccharide vaccination in HIV-infected children on highly active antiretroviral therapy

BACKGROUND

The capacity of pneumococcal vaccination to confer memory in HIV-infected children is critical for durable protection.

METHODS

HIV-infected children 2-<19 years administered two doses of pneumococcal conjugate vaccine (PCV7) and one dose of polysaccharide vaccine (PPV) on HAART were randomized 4-5 years later to receive a PCV7 or PPV booster. Total and high avidity antibodies to serotypes 1 (PPV) and 6B and 14 (PCV7 and PPV) were determined by ELISA. Memory was defined as persistence of ≥ 0.5 mcg/mL of serotype-specific antibody on day 0 or change from <0.5 mcg/mL to ≥ 0.5 mcg/mL between day 0 and week 1, or, ≥ 4-fold antibody rise between day 0 and week 1.

RESULTS

Prior to boosting, 4-5 years after the previous PCV7-PCV7-PPV series, geometric mean concentrations (GMCs) were 0.46 mcg/mL (serotype 1), 1.31 mcg/mL (serotype 6B), and 1.47 mcg/mL (serotype 14), with concentrations ≥ 0.5 mcg/mL in 41% (serotype 1) to 82% (serotypes 6B and 14). Memory based on antibody concentration ≥ 0.5 mcg/mL before or 1 week after boosting with PCV7 or PPV was demonstrated in 42-61% for serotype 1 and 87-94% for serotypes 6B and 14, with lower rates based on day 0 to week 1 ≥ 4-fold antibody rise (serotype 1, 3-13%; serotype 6B, 13-31%; serotype 14, 29-53%). Antibody concentrations post-boosting were greater following PCV7 than PPV for serotypes 6B and 14. Ratios of highly avid to total antibody pre- and post-boosting were 0.5-0.8. Predictors of memory included higher CD4% (nadir before HAART and at P1024 and P1061s entry), CD19% (at P1024 and P1061s entry), and antibody response after the PCV7-PCV7-PPV primary series and lower viral load (at P1024 and P1061s entry) and age.

CONCLUSIONS

Protective antibody concentrations, high avidity, and booster responses to PCV7 or PPV indicative of memory were present 4-5 years after PCV7-PCV7-PPV in HIV-infected children on HAART.

Use of the 13-valent pneumococcal conjugate vaccine in children and adolescents aged 6 - 17 years

INTRODUCTION

The introduction of pneumococcal conjugate vaccines into infant immunization schedules has successfully reduced the incidence of pneumococcal disease caused by vaccine serotypes. Disease incidence is low in healthy 6 - 17-year-old children and young people; however, there are a number of clinical conditions that put individuals in this age group at increased risk. Expansion of the license of a 13-valent pneumococcal conjugate vaccine , PCV-13, to include the 6 - 17 age group has recently been approved by European and American regulatory bodies.

AREAS COVERED

Studies assessing the safety, immunogenicity, and efficacy of pneumococcal conjugate vaccines in both healthy and high-risk 6 - 17-year-old children and adolescents are covered and the potential impact of PCV-13 in these populations is discussed. The use of the 23-valent pneumococcal polysaccharide vaccine, PPV-23, in high-risk children and adolescents is also considered.

EXPERT OPINION

Expanding the use of PCV-13 to include high-risk children and adolescents aged 6 - 17 has the potential to prevent additional cases of disease; however, vaccination of this population may no longer be necessary when herd immunity to PCV-13 serotypes becomes fully established. Despite the broader serotype coverage of PPV-23, the benefits of this vaccine in high-risk populations are uncertain.

Vaccination in HIV-infected individuals

Vaccinations are key to limiting the increased risk of severe infectious diseases in HIV-infected patients for whom the risk–benefit ratio has been re-evaluated. Vaccine safety and immunogenicity depend on both vaccine type and immune deficiency, while vaccine-induced immune activation promotes a transient increase in viral load. Vaccine immunogenicity is reduced and wanes more rapidly, strengthening the need for revaccination. While inactivated vaccines are safe, attenuated vaccines are theoretically contraindicated, but the risk of infectious diseases outweighs the risks of severe adverse events in endemic areas, where the majority of HIV-infected individuals live, thus allowing their use when immune deficiency is moderate. Immune reconstitution with HAART has improved vaccine immune response, highlighting the importance of global access to and early initiation of therapy.