Invasive pneumococcal disease among children with and without sickle cell disease in the United States, 1998 to 2009

Immunization adherence among children with sickle cell disease and sickle cell trait: Results of a population-based study

INTRODUCTION

Despite the importance of timely vaccine completion for protection from infectious disease, there is limited knowledge of the immunization adherence rates of children with sickle cell disease (SCD).

METHODS

This is a retrospective cohort study comparing the immunization rates of children with SCD to those with sickle cell trait between 2008 and 2019 in Georgia. Completion rates for each vaccine and the proportion of children with up-to-date status at 24 and 35 months were calculated and compared between the cohorts. Chi-square tests with odds ratios (OR) for differences and 95% confidence intervals (CIs) were reported on the overall up-to-date rates and rates for individual vaccines at 24 and 35 months for the two cohorts.

RESULTS

Children with SCD had higher up-to-date rates than children with sickle cell trait at 24 and 35 months. At 35 months, the overall up-to-date rates (OR = 1.17; 95% CI, 1.04-1.31; p = .004) and the four-dose pneumococcal conjugate vaccine series (OR = 1.36; 95% CI, 1.18-1.57; p < .001) were significantly different between the groups. Both cohorts had the highest completion rates for the hepatitis B series and the lowest rates for the varicella vaccine. Doses of diphtheria, tetanus, and acellular pertussis vaccine; varicella; and pneumococcal conjugate vaccines were most commonly missed by children in both cohorts.

CONCLUSIONS

Children with SCD have better immunization coverage than children with sickle cell trait, but there is an opportunity for improvement. Policymakers and healthcare professionals should focus on increasing access to care coordination services among children with SCD to ensure on-time and preventive healthcare services.

Respiratory management of acute chest syndrome in children with sickle cell disease

Acute chest syndrome (ACS) is a leading cause of respiratory distress and hospitalisation in children with sickle cell disease (SCD). The aetiology is multifactorial and includes fat embolism, venous thromboembolism, alveolar hypoventilation and respiratory infections, with the latter being particularly common in children. These triggers contribute to a vicious cycle of erythrocyte sickling, adhesion to the endothelium, haemolysis, vaso-occlusion and ventilation-perfusion mismatch in the lungs, resulting in the clinical manifestations of ACS. The clinical presentation includes fever, chest pain, dyspnoea, cough, wheeze and hypoxia, accompanied by a new pulmonary infiltrate on chest radiography. Respiratory symptoms may overlap with those of acute asthma, which may be difficult to distinguish. Patients with ACS may deteriorate rapidly; thus prevention, early recognition and aggressive, multidisciplinary team management is essential. In this narrative review, we highlight the current evidence regarding the epidemiology, pathophysiology, treatment and preventative strategies for ACS, focusing on the aspects of major interest for the paediatric pulmonologist and multidisciplinary team who manage children with SCD.

Pneumococcal infections in children with sickle cell disease before and after pneumococcal conjugate vaccines

Children with sickle cell disease (SCD) are at increased risk of invasive pneumococcal disease (IPD). Over 25 years, the Georgia Emerging Infections Program/Centers for Disease Control and Prevention Active Bacterial Core Surveillance network identified 104 IPD episodes among 3707 children with hemoglobin SS (HbSS) or HbSC aged <10 years, representing 6% of IPD in Black or African American children residing in Metropolitan Atlanta (reference population). Children with IPD and HbSS/SC were older than those with IPD in the reference population (P < .001). From 1994-1999 to 2010-2018, IPD declined by 87% in children with HbSS aged 0 to 4 years, and by 80% in those aged 5 to 9 years. However, IPD incidence rate ratios when comparing children with SCD with the reference population increased from 20.2 to 29.2 over these periods. Among children with HbSS and IPD, death declined from 14% to 3% after 2002, and meningitis declined from 16% to 8%. Penicillin resistance was more prevalent in children with SCD before 7-valent pneumococcal conjugate vaccine (PCV7) licensure. After 2010, all IPD serotypes were not included in the 13-valent PCV (PCV13). Within 3 years of vaccination, the effectiveness of the 23-valent pneumococcal polysaccharide vaccine (PPSV23) against non-PCV13 serotypes included in PPSV23 plus 15A/15C was 92% (95% confidence interval, 40.8- 99.0, P = .014; indirect-cohort effect adjusted for age and hydroxyurea). PPSV23 would cover 62% of non-PCV13 serotype IPD in children with SCD, whereas PCV15, PCV20, and PCV21/V116 (in development) could cover 16%, 51%, and 92%, respectively. Although less frequent, IPD remains a life-threatening risk in children with SCD. Effective vaccines with broader coverage could benefit these children.

Penicillin Prophylaxis in Patients With Sickle Cell Disease Beyond Age 5 Years

OBJECTIVE

Patients with sickle cell disease (SCD) are at increased risk for invasive pneumococcal disease (IPD) caused by Streptococcus pneumoniae. Immunization and antimicrobial prophylaxis may prevent this complication, and landmark clinical trials support discontinuation of antimicrobial prophylaxis at age 5 years. However, antimicrobial prophylaxis continues in some patients indefinitely. The objective of this study was to evaluate the incidence of culture-positive IPD and other infections in the setting of penicillin prophylaxis in the pediatric SCD population.

METHODS

This was a single-center, retrospective cohort study of patients with SCD who continued antimicrobial prophylaxis with penicillin, compared with those whose antimicrobial prophylaxis was discontinued. Included patients were aged 5 to 18 years during the study period and had no history of IPD or surgical splenectomy. Patient charts were reviewed for demographics, immunizations, penicillin prescription history, and microbiologic culture data.

RESULTS

Antimicrobial prophylaxis continued beyond age 5 years in 65% of patients, a higher percentage of whom had hemoglobin SS or S beta-zero disease. No patients whose antimicrobial prophylaxis was discontinued experienced IPD; 1 patient who continued antimicrobial prophylaxis died of S pneumoniae sepsis. Rates of other infections were comparable between groups (21% in prophylaxis versus 18% in no prophylaxis).

CONCLUSIONS

These results support appropriate de-prescribing of antimicrobial prophylaxis in patients with SCD who are not at high risk for IPD. Further multicenter studies are needed to evaluate consequences of antimicrobial prophylaxis with alternative agents on antibiotic resistance, examine provider rationale for continuation of antimicrobial prophylaxis, and assess quality of life effects (e.g., medication adherence, adverse drug reactions) of antimicrobial prophylaxis.

Operationalizing Appropriate Sepsis Definitions in Children Worldwide: Considerations for the Pediatric Sepsis Definition Taskforce

Sepsis is a leading cause of global mortality in children, yet definitions for pediatric sepsis are outdated and lack global applicability and validity. In adults, the Sepsis-3 Definition Taskforce queried databases from high-income countries to develop and validate the criteria. The merit of this definition has been widely acknowledged; however, important considerations about less-resourced and more diverse settings pose challenges to its use globally. To improve applicability and relevance globally, the Pediatric Sepsis Definition Taskforce sought to develop a conceptual framework and rationale of the critical aspects and context-specific factors that must be considered for the optimal operationalization of future pediatric sepsis definitions. It is important to address challenges in developing a set of pediatric sepsis criteria which capture manifestations of illnesses with vastly different etiologies and underlying mechanisms. Ideal criteria need to be unambiguous, and capable of adapting to the different contexts in which children with suspected infections are present around the globe. Additionally, criteria need to facilitate early recognition and timely escalation of treatment to prevent progression and limit life-threatening organ dysfunction. To address these challenges, locally adaptable solutions are required, which permit individualized care based on available resources and the pretest probability of sepsis. This should facilitate affordable diagnostics which support risk stratification and prediction of likely treatment responses, and solutions for locally relevant outcome measures. For this purpose, global collaborative databases need to be established, using minimum variable datasets from routinely collected data. In summary, a "Think globally, act locally" approach is required.

Bacterial Meningitis in Children With Sickle Cell Disease in Angola

Sickle cell disease (SCD) was found in 10% of children with bacterial meningitis (BM) in Luanda, 5-fold more than in the general population. BM children with SCD versus BM children without SCD had higher inflammatory markers, more often had pneumococcal meningitis (71% vs. 39%), and either died (39% vs. 22%) or had a longer hospital stay (15 vs. 11 days).

The Impact of Standardized Infectious Diseases Consultation on Post-Splenectomy Care and Outcomes

Background

Patients who receive splenectomy are at risk for overwhelming postsplenectomy infection (OPSI). Guidelines recommend that adult asplenic patients receive a complement of vaccinations, education on the risks of OPSI, and on-demand antibiotics. However, prior literature suggests a majority of patients who have had a splenectomy receive incomplete asplenic patient care and thus remain at increased risk. This study assessed the impact of standardized involvement of infectious diseases (ID) providers on asplenic patient care outcomes in patients undergoing splenectomy.

Methods

A quasi-experimental study design compared a prospective cohort of patients undergoing splenectomy from August 2017 to June 2021 who received standardized ID involvement in care of the asplenic patient with a historic control cohort of patients undergoing splenectomy at the same institution from January 2010 through July 2017 who did not. There were 11 components of asplenic patient care defined as primary outcomes. Secondary outcomes included the occurrence of OPSI, death, and death from OPSI.

Results

50 patients were included in the prospective intervention cohort and 128 in the historic control cohort. There were significant improvements in 9 of the 11 primary outcomes in the intervention arm as compared to the historic controls. Survival analysis showed no statistically significant difference in the incidence of OPSI-free survival between the groups (p = 0.056), though there was a trend towards improvement in the prospective intervention arm.

Conclusions

Standardized involvement of an ID provider in the care of patients undergoing splenectomy improves asplenic patient care outcomes. Routine involvement of ID in this setting may be warranted.

Considerations When Aggregating Data to Measure Performance Across Levels of the Health Care System

BACKGROUND

Measuring quality at varying levels of the health care system requires attribution, a process of determining the patients and services for which each level is responsible. However, it is important to ensure that attribution approaches are equitable; otherwise, individuals may be assigned differentially based upon social determinants of health.

METHODS

First, we used Medicaid claims (2010-2018) from Michigan to assess the proportion of children with sickle cell anemia who had less than 12 months enrollment within a single Medicaid health plan and could therefore not be attributed to a specific health plan. Second, we used the Medicaid Analytic eXtract data (2008-2009) from 26 states to simulate adapting the 30-Day Pediatric All-Condition Readmission measure to the Accountable Care Organization (ACO) level and examined the proportion of readmissions that could not be attributed.

RESULTS

For the sickle cell measure, an average of 300 children with sickle cell anemia were enrolled in Michigan Medicaid each year. The proportion of children that could not be attributed to a Medicaid health plan ranged from 12.2% to 89.0% across years. For the readmissions measure, of the 1,051,365 index admissions, 22% were excluded in the ACO-level analysis because of being unable to attribute the patient to a health plan for the 30 days post discharge.

CONCLUSIONS

When applying attribution models, it is essential to consider the potential to induce health disparities. Differential attribution may have unintentional consequences that deepen health disparities, particularly when considering incentive programs for health plans to improve the quality of care.

Influenza vaccination rates and hospitalizations among Medicaid enrollees with and without sickle cell disease, 2009-2015

BACKGROUND

Personswith sickle cell disease (SCD) face increased risks for pulmonary and infection-related complications. This study examines influenza vaccination coverage and estimates influenza-related morbidity among Medicaid enrollees with and without SCD.

PROCEDURE

Influenza vaccination coverage and hospitalizations related to influenza and pneumonia/acute chest syndrome (ACS) during each influenza season from 2009-2010 to 2014-2015 were assessed among enrollees in the IBM MarketScan® Multi-State Medicaid Database. Enrollees with SCD were identified as enrollees with greater than or equal to three claims listing SCD within a 5-year period during 2003-2017. Vaccinations were identified in outpatient claims. Hospitalizations associated with influenza or pneumonia/ACS were identified using inpatient claims. This study includes a series of cross-sectional assessments by season.

RESULTS

From 2009-2010 through 2014-2015 seasons, the SCD sample ranged from 5044 to 8651 enrollees; the non-SCD sample ranged from 1,841,756 to 3,796,337 enrollees. Influenza vaccination coverage was higher among enrollees with SCD compared with enrollees without SCD for all seasons (24.5%-33.6% and 18.2%-22.0%, respectively). Age-standardized rates of influenza-related hospitalizations were 20-42 times higher among SCD enrollees compared with non-SCD enrollees, and ACS/pneumonia hospitalizations were 18-29 times higher. Among enrollees with SCD, influenza-related hospitalization rates were highest among children aged 0-9 years. Among enrollees without SCD, influenza-related hospitalization rates were highest among adults aged 40-64 years.

CONCLUSIONS

Although vaccine coverage was higher in persons with versus without SCD, efforts to increase influenza coverage further are warranted for this high-risk group, who experienced markedly higher rates of influenza and ACS/pneumonia hospitalizations during each season.

Primary Immunization Series Coverage of Children With Sickle Cell Disease

INTRODUCTION

Children with sickle cell disease are at increased risk of serious infections, many of which can be prevented by receipt of recommended immunizations. Study objectives were to (1) assess the primary immunization series coverage among children with sickle cell disease and (2) compare the coverage with that of those without sickle cell disease.

METHODS

The Michigan Care Improvement Registry was used to obtain primary immunization series doses and sickle cell disease status for all eligible children in Michigan born in 2001-2016 (analysis was conducted in 2019). Completion of series and each individual vaccine were assessed for every child at ages 19 and 35 months. Proportions were stratified by sickle cell disease status and compared using chi-square tests. Logistic regression was used to model the odds of completing the series at each age, as predicted by sickle cell disease status and adjusting for the presence of Medicaid identification number.

RESULTS

The proportion of children who completed the immunization series was higher for those with sickle cell disease than for those without sickle cell disease at 19 months (58.5% vs 48.0%) and 35 months (74.7% vs 59.6%) (both p<0.0001). The odds of completing the series were 1.4 times higher at 19 months (95% CI=1.2, 1.6) and 1.7 times higher at 35 months (95% CI=1.5, 2.0) for children with sickle cell disease than for those without, adjusting for the presence of Medicaid identification number.

CONCLUSIONS

Although children with sickle cell disease had higher immunization rates than those without sickle cell disease, >40% of children with sickle cell disease did not receive all recommended immunizations by age 19 months. Immunization information systems should be utilized to improve routine immunization coverage of children with sickle cell disease.

Impact of PCV-13 vaccine on invasive pneumococcal disease in hospitalised children: A multi-institutional analysis

AIM

We aimed to describe changes in invasive pneumococcal disease (IPD) hospitalisations after introduction of the pneumococcal conjugate vaccine (PCV13).

METHODS

This was a retrospective analysis of the Pediatric Health Information System (PHIS) database, including children with IPD pre-PCV13 (2004-2009) and post-PCV13 (2012-2017). Healthy children and those with chronic conditions were analysed separately. The primary outcome was IPD incidence. Secondary outcomes included length of stay, intensive care unit (ICU) admission, mechanical ventilation and mortality.

RESULTS

9160 hospitalisations for IPD were included. The IPD rate per 100 000 discharges was 180 pre-PVC13 and 150 post-PCV13 [17% decrease (P = 0.085)]. The observed IPD rate in 2017 was 45.5% lower than the rate predicted by the pre-PCV13 trend (95% CI: 44%-46%). While a significant decrease in IPD (32%, P = 0.026) was observed among healthy children, there was no change in those with chronic conditions (9%, P = 0.24). In the post-PCV13 period, more IPD patients had chronic conditions, ICU admissions and longer ICU stays.

CONCLUSION

Although there was no overall reduction in IPD after PCV13, we observed a significant decrease in IPD among healthy patients. Further research is needed to elucidate microbiology or other factors contributing to persistent IPD hospitalisations.

Trends in Sickle Cell Disease-Related Mortality in the United States, 1979 to 2017

STUDY OBJECTIVE

We provide an updated assessment of trends in sickle cell disease (SCD)-related mortality, a significant source of mortality in the United States among black persons, using 1979 to 2017 US mortality data.

METHODS

SCD-related deaths were identified with International Classification of Diseases codes. Because SCD-related death is rare in other races, the analysis focused on black decedents. Age-specific and average annual SCD-related death rates were calculated. Causes of death codes were categorized into 20 groups relevant to SCD outcomes. SCD-related deaths were compared with non-SCD-related deaths after matching on race, sex, age group, and year of death.

RESULTS

There were 25,665 SCD-related deaths reported among blacks in the United States from 1979 through 2017. During that period, the annual SCD-related death rate declined in children and increased in adults, and the median age at death increased from 28 to 43 years. Acute causes of death, such as infection and cerebrovascular complications, were more common in younger age groups. Chronic complications were more common in adults. SCD-related deaths were more likely to be related to acute cardiac, pulmonary, and cerebrovascular complications; acute infections; and chronic cardiac and pulmonary complications and renal disorders; and less likely to be related to drug overdose and chronic infections than non-SCD-related deaths.

CONCLUSION

These data indicate SCD-related deaths are now more likely to be related to chronic complications of the disease than to acute complications. More research regarding prevention and treatment of chronic complications of SCD is necessary because persons with SCD are living longer.

Comparison of pneumococcal vaccination response in children with sickle cell disease: HbSS and HbSC

INTRODUCTION

Sickle cell disease (SCD) children are at increased risk of invasive pneumococcal disease and rely on penicillin prophylaxis and vaccination for infection prevention. Post-vaccination antibody levels in SCD may wane overtime. HbSC are believed to have better immunological response than HbSS.

OBJECTIVE

To compare antibody response to 23-valent pneumococcal polysaccharide vaccine (PPSV-23) between HbSS and HbSC.

METHODS

Patients with HbSS (n=33) and HbSC (n=11), aged 7-18 years, were prospectively recruited. Luminex pneumococcal antibody levels were measured for 23-serotypes, after two PPSV-23 doses.

RESULTS

Absolute median titer for 20 of the 23 serotypes was higher in HbSC than HbSS and significantly higher for serotypes 22 (3.9 vs. 1.6mcg/ml; p=0.039) and 43 (2.9 vs. 0.8mcg/ml; p=0.007). HbSC mounted a better immune anti-pneumococcal response compared to HbSS (≥1.3mcg/ml) for 18 of 23 serotypes, albeit not significant for any of the serotypes. More HbSC (64%) than HbSS (42%) were good vaccine responders (p=0.303). Two of 21 (10%) good vaccine responders and nine of 23 (39%) poor vaccine responders SCD participants subsequently developed acute chest syndrome or pneumonia (p=0.036). None of the HbSC patients developed ACS after receiving PPSV-23. HbSS poor vaccine responders were at increased future recurrence risk for ACS (p=0.003), pneumonia (p=0.036) or both (p=0.011), compared to good vaccine responders.

CONCLUSION

HbSC possess better pneumococcal vaccine response than HbSS. Poor vaccine response is concerning for future acute pulmonary events. Current vaccination strategy for SCD sub-types are lacking, therefore further study to evaluate utility of vaccine boosters is necessary.

Evaluation of Outcomes and Quality of Care in Children with Sickle Cell Disease Diagnosed by Newborn Screening: A Real-World Nation-Wide Study in France

This study's objective was to assess, on a national scale, residual risks of death, major disease-related events, and quality of care during the first five years in children diagnosed at birth with sickle cell disease (SCD). Data were retrospectively collected from medical files of all children with SCD born between 2006-2010 in France. Out of 1792 eligible subjects, 1620 patients (71.8% SS or S/beta°-thalassemia -SB°-) had available follow-up data, across 69 centers. Overall probability of survival by five years was 98.9%, with 12/18 deaths related to SCD. Probability of overt stroke by five years in SS/SB° patients was 1.1%, while transcranial Doppler (TCD) was performed in 81% before three years of age. A total of 26 patients had meningitis/septicemia (pneumococcal in eight cases). Prophylactic penicillin was started at a median age of 2.2 months and 87% of children had received appropriate conjugate pneumococcal vaccination at one year. By five years, the probability of survival without SCD-related events was 10.7% for SS/SB° patients. In contrast, hydroxyurea was prescribed in 13.7% and bone marrow transplant performed in nine patients only. In this study, residual risks of severe complications were low, probably resulting from a good national TCD, vaccination, and healthcare system coverage. Nonetheless, burden of disease remained high, stressing the need for disease-modifying or curative therapy.

Incidence of invasive Haemophilus influenzae infections in children with sickle cell disease

BACKGROUND

Children with sickle cell disease (SCD) are at increased risk for invasive infection with encapsulated bacteria. Antibiotic prophylaxis and immunizations against Streptococcus pneumoniae and Haemophilus influenzae type b (Hib) have decreased the overall incidence of invasive infections and have shifted distribution of serotypes causing disease toward those not covered by immunizations. We sought to determine the current incidence of invasive H. influenzae infections in children with SCD and to describe the clinical features and management of these infections.

METHODS

Microbiology reports of a large pediatric tertiary care center were reviewed to identify all isolates of H. influenzae detected in sterile body fluid cultures from January 1, 2010 to December 31, 2017. Results were compared with the center's comprehensive clinical database of all children with SCD to identify all cases of children ages 0 to18 years with SCD with invasive H. influenzae disease for the same time period.

RESULTS

We captured 2444 patients with SCD, with 14,336 person-years. There were eight episodes of H. influenzae bacteremia in seven children with SCD (five type f, two non-typable, one type a). Most episodes (7 of 8) were in children < 5 years. The incidence rate of invasive H. influenzae in SCD was 0.58/1000 person-years for ages 0 to 18 years and 1.60/1000 person-years for children age < 5 years. There were no deaths from H. influenzae infection.

CONCLUSIONS

In the era of universal antibiotic prophylaxis and immunization against Hib, invasive H. influenzae disease due to nonvaccine serotypes remains a risk for children with SCD, particularly those under five years of age.

Sickle Cell Clinical Research and Intervention Program (SCCRIP): A lifespan cohort study for sickle cell disease progression from the pediatric stage into adulthood

BACKGROUND

Previous natural history studies have advanced the understanding of sickle cell disease (SCD), but generally have not included sufficient lifespan data or investigation of the role of genetics in clinical outcomes, and have often occurred before the widespread use of disease-modifying therapies, such as hydroxyurea and chronic erythrocyte transfusions. To further advance knowledge of SCD, St. Jude Children's Research Hospital established the Sickle Cell Clinical Research and Intervention Program (SCCRIP), to conduct research in a clinically evaluated cohort of individuals with SCD across their lifetime.

PROCEDURES

Initiated in 2014, the SCCRIP study prospectively recruits patients diagnosed with SCD and includes retrospective and longitudinal collection of clinical, neurocognitive, geospatial, psychosocial, and health outcomes data. Biological samples are banked for future genomics and proteomics studies. The organizational structure of SCCRIP is based upon organ/system-specific working groups and is opened to the research community for partnerships.

RESULTS

As of August 2017, 1,044 (92.3% of eligible) patients with SCD have enrolled in the study (860 children and 184 adults), with 11,915 person-years of observation. Population demographics included mean age at last visit of 11.3 years (range 0.7-30.1), 49.8% females, 57.7% treated with hydroxyurea, 8.5% treated with monthly transfusions, and 62.9% hemoglobin (Hb) SS or HbSB⁰ -thalassemia, 25.7% HbSC, 8.4% HbsB⁺ -Thalassemia, 1.7% HbS/HPFH, and 1.2% other.

CONCLUSIONS

The SCCRIP cohort will provide a rich resource for the conduct of high impact multidisciplinary research in SCD.

Evaluation of newborn sickle cell screening programme in England: 2010-2016

OBJECTIVE

To evaluate England's NHS newborn sickle cell screening programme performance in children up to the age of 5 years.

DESIGN

Cohort of resident infants with sickle cell disease (SCD) born between 1 September 2010 and 31 August 2015 and followed until August 2016.

PARTICIPANTS

1317 infants with SCD were notified to the study from all centres in England and 1313 (99%) were followed up.

INTERVENTIONS

Early enrolment in clinical follow-up, parental education and routine penicillin prophylaxis.

MAIN OUTCOME MEASURES

Age seen by a specialist clinician, age at prescription of penicillin prophylaxis and mortality.

RESULTS

All but two resident cases of SCD were identified through screening; one baby was enrolled in care after prenatal diagnosis; one baby whose parents refused newborn screening presented symptomatically. There were 1054/1313 (80.3%, 95% CI 78% to 82.4%) SCD cases seen by a specialist by 3 months of age and 1273/1313 (97%, 95% CI 95.9% to 97.8%) by 6 months. The percentage seen by 3 months increased from 77% in 2010 to 85.4% in 2015. 1038/1292 (80.3%, 95% CI 78.1% to 82.5%) were prescribed penicillin by 3 months of age and 1257/1292 (97.3%, 95% CI 96.3% to 98.1%) by 6 months. There were three SCD deaths <5 years caused by invasive pneumococcal disease (IPD) sensitive to penicillin.

CONCLUSION

The SCD screening programme is effective at detecting affected infants. Enrolment into specialist care is timely but below the programme standards. Mortality is reducing but adherence to antibiotic prophylaxis remains important for IPD serotypes not in the current vaccine schedule.

Risk of Invasive Pneumococcal Disease in Children with Sickle Cell Disease in England: A National Observational Cohort Study, 2010-2015

OBJECTIVE

To describe the clinical presentation, risk factors, serotype distribution and outcomes of invasive pneumococcal disease (IPD) in children with sickle cell disease (SCD) following the introduction of the 13-valent pneumococcal conjugate vaccine (PCV13) in the UK.

DESIGN

Prospective national newborn screening for SCD and enhanced national IPD surveillance.

PARTICIPANTS

Children with SCD born in England between 1 September 2010 and 31 August 2014 who developed laboratory-confirmed IPD by 31 December 2015.

MAIN OUTCOMES AND MEASURES

Risk of IPD in children with SCD compared with children without SCD during the surveillance period.

RESULTS

Eleven children homozygote for haemoglobin S (HbSS) and one double heterozygote for haemoglobin S and C (HbSC) developed IPD. Septicaemia (n=7) and lower respiratory tract infection (n=4) were the main clinical presentations, and serogroup 15 (not present in PCV13) was responsible for 73% (8/11) of cases. Three children with HbSS (27%) died compared with <5% nationally. Children with HbSS had a 49-fold (95% CI 27 to 89, P<0.001) higher risk of IPD compared with their peers without SCD.

CONCLUSIONS

Children with SCD remain at increased risk of IPD despite national newborn screening, early penicillin prophylaxis and high pneumococcal vaccine uptake. They are also more likely to die of their infection compared with their peers without SCD. Most IPD cases are now due to serotypes not covered by PCV13. Healthcare professionals need to work more closely with families with SCD and local communities to emphasise the importance of penicillin prophylaxis, explore barriers, allay misguided beliefs and facilitate rapid access to healthcare.

Ceftriaxone-induced drug reaction mimicking acute splenic sequestration crisis in a child with hemoglobin SC disease

BACKGROUND

Acute splenic sequestration crisis is a complication of sickle cell disease (SCD) occurring when intrasplenic red blood cell (RBC) sickling prevents blood from leaving the spleen, causing acute splenic enlargement. Although typically seen in young children, it has been reported in older children with hemoglobin (Hb)SC disease, eventually resulting in functional asplenia. Ceftriaxone is a frequently used antibiotic of choice for children with SCD, because of its efficacy against invasive pneumococcal disease.

CASE REPORT

We report a case of a 9-year-old female with HbSC disease, who had a fatal reaction after receiving a dose of ceftriaxone in the outpatient clinic for fever. Her Hb level decreased abruptly from 9.3 to 2.3 mg/dL. RBC clumps with no visible hemolysis were observed in the postreaction sample. Autopsy examination revealed marked splenomegaly with acute congestion and sickled cells in the spleen and liver. Serologic testing revealed a positive direct antiglobulin test with polyspecific antibody, anti-C3, and anti-C3d, but negative with anti-immunoglobulin G. Ceftriaxone-dependent RBC antibodies were detected in her serum and RBC eluate when tested in the presence of the drug.

CONCLUSION

We report a new presentation of ceftriaxone-induced drug reaction in a patient with SCD mimicking an acute splenic sequestration crisis. Review of the literature for cases of ceftriaxone-induced drug reactions in pediatric patients revealed nine previously reported cases of ceftriaxone-induced immune hemolytic anemia in children with SCD since 1995, but none with an initial presentation suggestive of acute splenic sequestration crisis.

Invasive pneumococcal disease in children with sickle cell disease in the pneumococcal conjugate vaccine era

Invasive pneumococcal disease (IPD) in children with sickle cell disease (SCD) can be devastating. We sought to assess the impact of IPD in children with SCD since licensure of the pneumococcal conjugate vaccines (PCVs). We found 11 cases of IPD giving an incidence of 417 per 100,000 person-years, much higher than that reported in children without SCD. Although all isolates were sensitive to penicillin, 89% of isolates were nonvaccine serotypes. Further study is needed to characterize the incidence of and risk factors for the development of IPD in SCD in the PCV era to help drive better prevention strategies.

Invasive Pneumococcal Disease in Patients With Sickle Cell Disease

BACKGROUND

Patients with sickle cell disease (SCD) are at risk of fatal sepsis with encapsulated bacteria, such as Streptococcus pneumoniae, because of the inherent autosplenectomy that occurs in SCD. This risk is thwarted with oral penicillin prophylaxis during the first 5 years of life, and with stringent vaccination against S. pneumoniae alongside routine childhood immunization. But compared with the general African American pediatric population, the rate of invasive pneumococcal disease (IPD) in patients with SCD still remains high, resulting in hospitalization and fatality.

METHODS

Patients with SCD who developed IPD from 2004 up to 2013 were identified using microbiology records. Descriptive analysis of presence of risk factors for IPD, type of SCD, pneumococcal vaccination and prophylaxis status, clinical presentation, microbiological data, and the outcome of IPD was performed.

RESULTS

Eight patients with SCD developed IPD (7 bacteremia and 1 respiratory tract infection). Three of the 8 isolates underwent serotype analysis (15 C in 2 and 15A in 1), none covered with the current vaccination program. One patient had fatal outcome (15A).

CONCLUSIONS

Breakthrough cases of IPD may involve nonvaccine isolates, and seem to occur after 5 years of age when oral penicillin prophylaxis has been terminated.

Alteration of lymphocyte phenotype and function in sickle cell anemia: Implications for vaccine responses

Individuals with sickle cell anemia (SCA) have increased susceptibility to infections, secondary to impairment of immune function. Besides the described dysfunction in innate immunity, including impaired opsonization and phagocytosis of bacteria, evidence of dysfunction of T and B lymphocytes in SCA has also been reported. This includes reduction in the proportion of circulating CD4+ and CD8+ T cells, reduction of CD4+ helper: CD8+ suppressor T cell ratio, aberrant activation and dysfunction of regulatory T cells (Treg ), skewing of CD4+ T cells towards Th2 response and loss of IgM-secreting CD27 + IgM(high) IgD(low) memory B cells. These changes occur on the background of immune activation characterized by predominance of memory CD4+ T cell phenotypes, increased Th17 signaling and elevated levels of C-reactive protein and pro-inflammatory cytokines IL-6 and TNF-α, which may affect the immunogenicity and protective efficacy of vaccines available to prevent infections in SCA. Thus, in order to optimize the use of vaccines in SCA, a thorough understanding of T and B lymphocyte functions and vaccine reactivity among individuals with SCA is needed. Studies should be encouraged of different SCA populations, including sub-Saharan Africa where the burden of SCA is highest. This article summarizes our current understanding of lymphocyte biology in SCA, and highlights areas that warrant future research. Am. J. Hematol. 91:938-946, 2016. © 2016 Wiley Periodicals, Inc.

Determining Adherence to Quality Indicators in Sickle Cell Anemia Using Multiple Data Sources

INTRODUCTION

Advances in primary prophylaxis have resulted in improved outcomes for patients with sickle cell anemia (SCA; i.e., hemoglobin SS- and Sβ(0)-thalassemia). Standard prophylactic measures include a first pneumococcal polysaccharide vaccine (PPV) and transcranial Doppler ultrasound (TCD) at age 2 years. Though efficacious, evidence suggests that delivery of these interventions is suboptimal. This study reports adherence to these measures and examines concordance across various data sources, using Registry and Surveillance for Hemoglobinopathies project data.

METHODS

Retrospective database and SCA center chart review identified children with SCA aged 24-36 months between January 1, 2004, and December 31, 2008. PPV and TCD administration were determined through Medicaid and Children's Health Insurance Program administrative claims data, medical record review, and Georgia Registry of Immunization Transaction and Services. Analysis was conducted in 2015.

RESULTS

A total of 125 children met inclusion criteria. Forty-five (36.0%) children had documentation of both interventions, whereas 19 (15.2%) had no documentation of either intervention. Sixty-one (48.8%) children obtained only one intervention. Of these, more were likely to have had PPV than TCD (77.0% vs 23.0%, respectively, p<0.001). Agreement between claims data and medical record review was moderate for PPV (κ=0.55) and substantial for TCD (κ=0.74).

CONCLUSIONS

No single, reliable data source for tracking standard of care for children with SCA statewide was found. According to study data, prophylaxis measures were not universally implemented during the surveillance period. Further research is needed to adequately track changes over time, determine risk groups, and develop methods of evaluating important metrics.

Wasting and stunting are still prevalent in children with sickle cell anaemia in Lagos, Nigeria

Background

Sickle cell anaemia (SCA) is associated with growth failure. However, recent reports indicate high rates of overweight or obesity among children with SCA in developed countries. It is unclear whether overweight or obesity is also common in children with SCA in developing countries. The objectives of the study were to determine the prevalence of overweight or obesity, wasting and stunting and identify predictors of wasting and stunting among children with SCA in Nigeria.

Method

Children with SCA attending a public-funded tertiary hospital clinic were studied. Weight, height, haemoglobin, haemoglobin fractions and white cell count were measured. Anthropometric values were converted to z scores and referenced to the WHO Child Growth Standards and WHO Reference 2007. The proportions with wasting, stunting and overweight or obesity were determined. Regression analysis was used to identify the predictors of wasting and stunting.

Results

Two hundred and thirty-three children [mean (±SD) age of 9.0 (±4.0) years, 60.9 % males] participated in the study. Wasting, stunting and overweight or obesity rates were 22.7 %, 11.6 % and 1.7 %, respectively. Boys and children from low socioeconomic class were 3.25 (1.45-7.29) and 2.42 (1.14-5.18) times more likely to be wasted respectively, while both wasting and stunting were more common with increasing age [adjusted OR of 1.33 (1.18-1.51) and 1.15 (1.01-1.32) respectively]. Sickle cell-related complications and intake of oral penicillin and hydroxyurea were not associated with wasting and stunting.

Conclusion

Overweight or obesity is uncommon while wasting and stunting are still prevalent in children with SCA in Lagos. The strongest predictors of wasting and stunting were older age, male gender and low socioeconomic status.

Improved Splenic Function After Hematopoietic Stem Cell Transplant for Sickle Cell Disease

BACKGROUND

Splenic dysfunction is a significant complication of sickle cell disease (SCD). Hematopoietic stem cell transplant (HSCT) is a proven cure for SCD; however, its long-term effect on splenic function is not well characterized.

PROCEDURE

We conducted a retrospective cohort study of pediatric patients who had HSCT for SCD at two transplant centers. (99m) Tc liver-spleen (LS) scans were blindly reviewed and classified as demonstrating absent, decreased, or normal splenic uptake.

RESULTS

Considering all engrafted nonsplenectomized Hb SS and Sβ(0) -thalassemia patients with LS scans available, at a median of 2.0 years post-HSCT (range 1.0-9.3 years) eight of 53 (15%) had normal, 40 of 53 (75%) decreased, and five of 53 (9%) absent splenic uptake. More patients had splenic uptake after HSCT: pre-HSCT 14/38 (37%) versus post-HSCT 34/38 (89%), P < 0.0001. Older age at HSCT was associated with worse splenic function post-HSCT (median age at HSCT for absent uptake 16.6 years vs. present uptake 8.0 years, P = 0.030). Extensive chronic GVHD was also more common in patients with absent splenic uptake compared to patients with present uptake (absent 40% vs. present 6%, P = 0.064).

CONCLUSIONS

HSCT significantly improves splenic function for most pediatric patients with SCD, but older patient age at time of HSCT and extensive chronic GVHD appear to be risk factors for poor post-HSCT splenic function.

The Saudi Thoracic Society pneumococcal vaccination guidelines-2016

Streptococcus pneumoniae (pneumococcus) is the leading cause of morbidity and mortality worldwide. Saudi Arabia is a host to millions of pilgrims who travel annually from all over the world for Umrah and the Hajj pilgrimages and are at risk of developing pneumococcal pneumonia or invasive pneumococcal disease (IPD). There is also the risk of transmission of S. pneumoniae including antibiotic resistant strains between pilgrims and their potential global spread upon their return. The country also has unique challenges posed by susceptible population to IPD due to people with hemoglobinopathies, younger age groups with chronic conditions, and growing problem of antibiotic resistance. Since the epidemiology of pneumococcal disease is constantly changing, with an increase in nonvaccine pneumococcal serotypes, vaccination policies on the effectiveness and usefulness of vaccines require regular revision. As part of the Saudi Thoracic Society (STS) commitment to promote the best practices in the field of respiratory diseases, we conducted a review of S. pneumoniae infections and the best evidence base available in the literature. The aim of the present study is to develop the STS pneumococcal vaccination guidelines for healthcare workers in Saudi Arabia. We recommend vaccination against pneumococcal infections for all children <5 years old, adults ≥50 years old, and people ≥6 years old with certain risk factors. These recommendations are based on the presence of a large number of comorbidities in Saudi Arabia population <50 years of age, many of whom have risk factors for contracting pneumococcal infections. A section for pneumococcal vaccination before the Umrah and Hajj pilgrimages is included as well.

2015 Clinical trials update in sickle cell anemia

Polymerization of HbS and cell sickling are the prime pathophysiological events in sickle cell disease (SCD). Over the last 30 years, a substantial understanding at the molecular level has been acquired on how a single amino acid change in the structure of the beta chain of hemoglobin leads to the explosive growth of the HbS polymer and the associated changes in red cell morphology. O2 tension and intracellular HbS concentration are the primary molecular drivers of this process, and are obvious targets for developing new therapies. However, polymerization and sickling are driving a complex network of associated cellular changes inside and outside of the erythrocyte, which become essential components of the inflammatory vasculopathy and result in a large range of potential acute and chronic organ damages. In these areas, a multitude of new targets for therapeutic developments have emerged, with several ongoing or planned new therapeutic interventions. This review outlines the key points of SCD pathophysiology as they relate to the development of new therapies, both at the pre-clinical and clinical levels.

13-valent pneumococcal conjugate vaccine (PCV13) is immunogenic and safe in children 6-17 years of age with sickle cell disease previously vaccinated with 23-valent pneumococcal polysaccharide vaccine (PPSV23): Results of a phase 3 study

BACKGROUND

A large population of older children with sickle cell disease (SCD) is currently vaccinated with only 23-valent pneumococcal polysaccharide vaccine (PPSV23). In immunocompetent adults, PPSV23 vaccination reduces immune responses to subsequent vaccination with a pneumococcal vaccine. The 13-valent pneumococcal conjugate vaccine (PCV13), which addresses this limitation, may offer an advantage to this population at high risk of pneumococcal disease.

PROCEDURE

Children with SCD 6-17 years of age previously vaccinated with PPSV23 at least 6 months before study enrollment received two doses of PCV13 6 months apart. Anti-pneumococcal polysaccharide immunoglobulin G (IgG) geometric mean concentrations (GMCs) and opsonophagocytic activity (OPA) geometric mean titers (GMTs) were measured before, 1 month after each administration, and 1 year after the second administration.

RESULTS

Following each PCV13 administration, IgG GMCs and OPA GMTs significantly increased, and antibody levels after doses 1 and 2 were generally comparable. Antibody levels declined over the year following dose 2. At 1 year after the second administration, OPA GMTs for all and IgG GMCs for most serotypes remained above pre-vaccination levels. Most adverse events were due to vaso-occlusive crises, a characteristic of the underlying condition of SCD.

CONCLUSIONS

Children with SCD who were previously vaccinated with PPSV23 responded well to 1 PCV13 dose, and a second dose did not increase antibody response. PCV13 antibodies persisted above pre-vaccination levels for all serotypes 1 year after dose 2. Children with SCD may benefit from at least one dose of PCV13.

Epidemiological burden of invasive pneumococcal disease in children and adolescents with predisposing risk factors

OBJECTIVE

Some medical conditions constitute important risk factors for the development of invasive pneumococcal diseases in children and adolescents aged from 5 to 19 years. Conjugate vaccines have potential efficacy in this scenario, but are not available in many Latin American public healthcare systems for this age group. This study aimed to estimate the preventable fraction of invasive pneumococcal diseases among individuals aged from 5 to 19 years with associated risk factors for its development.

METHODS

Data regarding the Latin America population, risk factors prevalence and conjugate vaccines efficacy were obtained from the literature.

RESULTS

Total population at risk ranged from 17.3 to 64.6 million of individuals and asthma was the most impacting risk factor. According to SIREVA, PCV13 provided a 62.9% serotypes coverage in individuals from 5 to 29 years in 2012, potentially increasing the covered population from [8,338,457-31,057,620] with PCV10 to [10,906,356-40,622,078] with PCV13. To date, according to available efficacy data, the hypothetically immunized population ranged from 11.4 to 42.4 million, representing 7.0% to 26.0% of the total population in this age group.

CONCLUSIONS

Vaccination in risk groups should be encouraged, as it potentially contributes to the reduction in the number of cases of invasive pneumococcal disease.

Vaccination, underlying comorbidities, and risk of invasive pneumococcal disease

OBJECTIVES

Children with underlying conditions remain at increased risk for invasive pneumococcal diseases (IPD). This study describes the epidemiology, serotype distribution, clinical presentations, and outcomes of IPD in children with and without comorbidity.

METHODS

Cases of childhood IPD in Massachusetts were identified via enhanced surveillance from 2002 through 2014. Demographic and clinical data were collected via follow-up telephone interviews with parents and/or primary care providers. Underlying conditions were classified according to the 2012 Report of the Committee on Infectious Diseases and 2013 recommendations by the Advisory Committee on Immunization Practices.

RESULTS

Among 1052 IPD cases in Massachusetts children <18 years old, 22.1% had at least 1 comorbidity. Immunocompromising conditions (32.7%) and chronic respiratory diseases (22.4%) were most common. Children with comorbidities were older at the time of IPD diagnosis (median 54 vs 23 months, P < .001), had higher hospitalization (odds ratio 2.5; 95% confidence interval 1.7-3.6) and case-fatality rates (odds ratio 3.7; 95% confidence interval 1.5-8.9) compared with children without known underlying conditions after adjusting for age, gender, year of diagnosis, and pneumococcal vaccination status. During the last 2 years of the study, IPD among children with comorbidities was caused by non-pneumococcal conjugate vaccine 13 serotypes in 23-valent polysaccharide pneumococcal vaccine (6/12, 50%) or serotypes that are not included in any of the vaccines (6/12; 50%).

CONCLUSIONS

In children with comorbidity, IPD results in higher mortality, and a large proportion of disease is due to serotypes not included in current conjugate vaccines. Further research is needed, specifically to develop and evaluate additional strategies for prevention of IPD in the most vulnerable children.

Genomic analyses of pneumococci from children with sickle cell disease expose host-specific bacterial adaptations and deficits in current interventions

Sickle cell disease (SCD) patients are at high risk of contracting pneumococcal infection. To address this risk, they receive pneumococcal vaccines, and antibiotic prophylaxis and treatment. To assess the impact of SCD and these interventions on pneumococcal genetic architecture, we examined the genomes of more than 300 pneumococcal isolates from SCD patients over 20 years. Modern SCD strains retained invasive capacity but shifted away from the serotypes used in vaccines. These strains had specific genetic changes related to antibiotic resistance, capsule biosynthesis, metabolism, and metal transport. A murine SCD model coupled with Tn-seq mutagenesis identified 60 noncapsular pneumococcal genes under differential selective pressure in SCD, which correlated with aspects of SCD pathophysiology. Further, virulence determinants in the SCD context were distinct from the general population, and protective capacity of potential antigens was lost over time in SCD. This highlights the importance of understanding bacterial pathogenesis in the context of high-risk individuals.

Mortality of New York children with sickle cell disease identified through newborn screening

PURPOSE

Long-term follow-up of newborn screening for conditions such as sickle cell disease can be conducted using linkages to population-based data. We sought to estimate childhood sickle cell disease mortality and risk factors among a statewide birth cohort with sickle cell disease identified through newborn screening.

METHODS

Children with sickle cell disease identified by newborn screening and born to New York residents in 2000-2008 were matched to birth and death certificates. Mortality rates were calculated (using numbers of deaths and observed person-years at risk) and compared with mortality rates for all New York children by maternal race/ethnicity. Stratified analyses were conducted to examine associations between selected factors and mortality.

RESULTS

Among 1,911 infants with sickle cell disease matched to birth certificates, 21 deaths were identified. All-cause mortality following diagnosis was 3.8 per 1,000 person-years in the first 2 years of life and 1.0 per 1,000 person-years at ages 2-9 years. The mortality rate was significantly lower among children of foreign-born mothers and was significantly higher among preterm infants with low birth weight. The mortality rates were not significantly higher for infants after 28 days with sickle cell disease than for all New York births, but they were 2.7-8.4 times higher for children 1 through 9 years old with homozygous sickle cell disease than for those of all non-Hispanic black or Hispanic children born to New York residents.

CONCLUSION

Estimated mortality risk in children with homozygous sickle cell disease remains elevated even after adjustment for maternal race/ethnicity. These results provide evidence regarding the current burden of child mortality among children with sickle cell disease despite newborn screening.Genet Med 17 6, 452-459.

Where does a Staphylococcus aureus vaccine stand?

In this review, we examine the current status of Staphylococcus aureus vaccine development and the prospects for future vaccines. Examination of the clinical trials to date show that murine models have not predicted success in humans for active or passive immunization. A key factor in the failure to develop a vaccine to prevent S. aureus infections comes from our relatively limited knowledge of human protective immunity. More recent reports on the elements of the human immune response to staphylococci are analysed. In addition, there is some controversy concerning the role of antibodies for protecting humans, and these data are reviewed. From a review of the current state of understanding of staphylococcal immunity, a working model is proposed. Some new work has provided some initial candidate biomarker(s) to predict outcomes of invasive infections and to predict the efficacy of antibiotic therapy in humans. We conclude by looking to the future through the perspective of lessons gleaned from the clinical vaccine trials.

Invasive pneumococcal disease in children can reveal a primary immunodeficiency

BACKGROUND

About 10% of pediatric patients with invasive pneumococcal disease (IPD) die from the disease. Some primary immunodeficiencies (PIDs) are known to confer predisposition to IPD. However, a systematic search for these PIDs has never been carried out in children presenting with IPD.

METHODS

We prospectively identified pediatric cases of IPD requiring hospitalization between 2005 and 2011 in 28 pediatric wards throughout France. IPD was defined as a positive pneumococcal culture, polymerase chain reaction result, and/or soluble antigen detection at a normally sterile site. The immunological assessment included abdominal ultrasound, whole-blood counts and smears, determinations of plasma immunoglobulin and complement levels, and the evaluation of proinflammatory cytokines.

RESULTS

We included 163 children with IPD (male-to-female ratio, 1.3; median age, 13 months). Seventeen children had recurrent IPD. Meningitis was the most frequent type of infection (87%); other infections included pleuropneumonitis, isolated bloodstream infection, osteomyelitis, endocarditis, and mastoiditis. One patient with recurrent meningitis had a congenital cerebrospinal fluid fistula. The results of immunological explorations were abnormal in 26 children (16%), and a PID was identified in 17 patients (10%), including 1 case of MyD88 deficiency, 3 of complement fraction C2 or C3 deficiencies, 1 of isolated congenital asplenia, and 2 of Bruton disease (X-linked agammaglobulinemia). The proportion of PIDs was much higher in children aged >2 years than in younger children (26% vs 3%; P < .001).

CONCLUSIONS

Children with IPD should undergo immunological investigations, particularly those aged >2 years, as PIDs may be discovered in up to 26% of cases.

Ambulatory quality indicators to prevent infection in sickle cell disease

The purpose of this study was to identify rates of adherence for three outpatient quality indicators noted by Wang et al. (Pediatrics 2011;128:484–493): (1) influenza vaccine, (2) pneumococcal immunizations, and (3)penicillin prophylaxis in patients with sickle cell disease (SCD) in a Medicaid sample. These variables were chosen based on Wang and colleagues' suggestion that these variables are important for the assessment of the quality of care of children with SCD. We hypothesized that the overall rate of adherence would be poor with adults having worse rates of adherence than children. We conducted a retrospective cohort study using the Wisconsin State Medicaid database over a 5-year period to assess the preventative medication adherence of individuals with SCD. Preventative medication variables in this study included influenza vaccination,pneumococcal immunizations (PCV7, PPV23), and penicillin prophylaxis. As predicted, the 2003–2007 Wisconsin State Medicaid database showed patients with SCD had low adherence in terms of recommended influenza vaccinations (21.58% adherent), PPV23 pneumococcal immunizations (43.47% adherent), and penicillin prophylaxis (18.18% adherent). Pneumococcal immunizations for PCV7 were higher than expected (77.27%adherent). Although children tended to adhere to recommended preventative medications more than adults,overall adherence was low. Although we cannot explain why adherence is low, it is likely due to multiple factors at the patient- and provider-level. We encourage patients and providers to create a partnership to meet adherence recommendations, and we describe our strategies for increasing adherence.