COVID-19 Immunization Coverage Among People With Sickle Cell Disease.

This cross-sectional study compares the completion of the primary COVID-19 vaccine series in Michigan residents with vs without sickle cell disease and by age group.

Adherence to hydroxyurea and clinical outcomes among children with sickle cell anemia.

OBJECTIVE: Hydroxyurea lowers the incidence of vaso-occlusive pain crises (VOC) and acute chest syndrome (ACS) among children with sickle cell anemia (SCA). Our objective was to assess the relationship between levels of adherence to hydroxyurea and clinical outcomes among children and adolescents with SCA. METHODS: This retrospective cohort study included Medicaid data (2005-2012) from Florida, Illinois, Louisiana, Michigan, South Carolina, and Texas. The study population consisted of children 1-17 years old with SCA enrolled in Medicaid for 3 years. Among children that initiated hydroxyurea, the medication possession ratio (MPR) was calculated as the proportion of days covered by hydroxyurea. Six months after initiation of hydroxyurea, clinical outcomes were assessed through the end of the study period: numbers of VOC-related inpatient admissions and emergency department visits, and encounters for ACS. Multivariable Poisson models were used to predict outcomes by MPR quartile adjusting for previous healthcare utilization, state, and age. RESULTS: Hydroxyurea was initiated by 515 children. The median MPR was 0.53 (interquartile range = 0.3-0.8). The annual median number of visits was 0.0 for ACS, 1.3 for VOC-related emergency department, and 1.4 for VOC-related inpatient admissions. For each outcome, the highest quartile of MPR had the lowest predicted count; this difference was significant for ACS visits when compared with the lowest quartile of MPR. CONCLUSION: This study demonstrated a high level of adherence (>75%) was essential to achieve a lower incidence of common negative clinical outcomes. Further, moderate and severe hydroxyurea nonadherence may be more common than previously appreciated among children, emphasizing the importance of developing and testing innovative strategies to increase adherence.

Changes in Hydroxyurea Use Among Youths Enrolled in Medicaid With Sickle Cell Anemia After 2014 Revision of Clinical Guidelines.

Importance: Youths with sickle cell anemia (SCA) are at risk of pain crises, stroke, and early death. Complications can be reduced by the oral disease-modifying medication hydroxyurea, and in 2014, the National Heart, Lung, and Blood Institute published revised guidelines that hydroxyurea should be offered to youths aged 9 months and older with SCA regardless of disease severity. Objective: To describe changes in hydroxyurea use among youths with SCA before and after release of the National Heart, Lung, and Blood Institute guidelines. Design, Setting, and Participants: This cross-sectional study was conducted using administrative data from 2010 to 2018 from Michigan and New York State (NYS) Medicaid programs. The study population included youths aged 1 to 17 years with SCA enrolled in the Michigan or NYS Medicaid programs for at least 1 year (Michigan: 2010-2018; NYS: 2012-2018). Youths with SCA were identified using validated claims-based definitions. Data were analyzed from June to October 2020. Main Outcomes and Measures: The main outcome was hydroxyurea use characterized as mean annual counts of days' supply of filled hydroxyurea prescriptions. Rates of hydroxyurea use over time were assessed using regression models (Michigan: zero-inflated negative binomial; NYS: negative binomial). Models included indicators for periods before and after guideline release. Results: A total of 4302 youths with SCA (2236 males [52.0%]; 2676 born 2005-2017 [62.2%]; 150 Hispanic [3.5%], 2929 non-Hispanic Black [68.0%], and 389 non-Hispanic White [9.0%]) contributed 12 565 person-years. The mean (SD) annual days' supply of hydroxyurea was 47.2 (93.6) days per youth in Michigan and 97.4 (137.0) days per youth in NYS. In Michigan, there was an increase in the odds of having nonzero days' supply after the guidelines were released (odds ratio, 1.52; 95% CI, 1.07-2.14). In NYS, no change was seen in the mean days' supply of filled hydroxyurea. Conclusions and Relevance: These findings suggest that hydroxyurea was substantially underused among youths with SCA, despite establishment as the primary disease-modifying therapy for SCA, and that there was incomplete clinician or patient uptake of newly released guidelines. Results suggest that expanding use of hydroxyurea may require a multifaceted approach that includes addressing multiple system- and patient-level barriers.

Influenza immunization coverage of children with sickle cell disease.

OBJECTIVES: To assess receipt of annual flu immunization among children living with sickle cell disease (SCD). METHODS: Receipt of flu immunization (2014-2019) by SCD status was assessed among all Michigan children <18 years of age using the statewide immunization registry. Logistic regression was used to estimate the odds of annual flu immunization by SCD status and age. RESULTS: Annual flu immunization coverage was higher among children with SCD (46.9%; n = 751) than without (23.2%; n = 2,012,846). The annual adjusted odds of flu immunization for those with SCD were 2.8 (95% CI: 2.5-3.1) times higher than for those without SCD; there were no significant differences by age among children with SCD. Among those without SCD, adolescents aged 13-17 were 2.2 (95% CI: 2.2-2.2) times less likely to receive annual flu immunization than children 6-35 months. CONCLUSIONS: Children with SCD had higher annual flu immunization rates than those without SCD, but >50% remain unimmunized.

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.