Abstract
Background
Children with sickle cell disease (SCD) are at high risk of complications from influenza and should receive an influenza vaccination seasonally. Despite this recommendation, vaccination rates remain suboptimal. Boston Medical Center (BMC) previously achieved high influenza vaccination rates among its pediatric patients with SCD. The purpose of this study was to determine whether this high vaccination rate has been maintained and whether it has influenced outcome measures.
Patients and Methods
A retrospective chart review was conducted in the hematology clinic at an urban, academic medical center. Fisher’s exact test and the independent samples t-test were used to determine if there were any significant differences in characteristics between patients with influenza and patients without influenza, as well as between vaccinated and unvaccinated patients. Influenza vaccination rate, influenza-related hospitalization rate, and influenza-positive rate were collected and compared with reported rates.
Results
Data from 124 pediatric patients with SCD were examined. The influenza vaccination rate for pediatric patients with SCD at BMC (90.32%) was higher than previous studies that were not conducted at BMC, while BMC’s influenza-related hospitalization rate (0) and influenza-positive rate (4.84%) were lower than other studies. Subjects who contracted influenza were younger than those who did not (4.67 vs. 10.03 years, p=0.005).
Conclusion
BMC has maintained a high influenza vaccination rate among pediatric patients with SCD. BMC’s vaccination strategy has been successful at improving outcome measures including rates of influenza and influenza hospitalizations without requiring additional staff. Such efforts should be replicated at other centers.
Keywords: sickle cell disease, influenza, vaccination
INTRODUCTION
Sickle cell disease (SCD) is a group of inherited blood disorders that affects nearly 100,000 individuals in the United States.1,2 SCD is associated with numerous complications, including acute chest syndrome (ACS) which is identified by the presence of new pulmonary infiltrate, as well as respiratory symptoms (including dyspnea and cough) and/or fever.3 ACS is a significant risk factor for early death and the second most frequent cause of hospitalization in patients with SCD (after vaso-occlusive crisis).4,5 Individuals with SCD have a high risk of complications caused by influenza partly because influenza has also been identified as a cause of ACS.6–9 One study determined that the influenza-related hospitalization (IRH) rate for pediatric patients with SCD was 56 times the rate of pediatric patients who did not have SCD.10
Individuals with SCD also have a high prevalence of asthma.11 Previous studies have found that asthma prevalence in individuals with SCD ranges from 17% to 48%.12 This is another potential cause of increased risk of complications due to influenza in patients with SCD, as children with asthma have a greater IRH rate compared to children without asthma.13 In addition, influenza can trigger acute asthma exacerbations and also increases the risk of emergency department treatment failure in children with asthma.14,15
The United States Department of Health and Human Services has set a goal of a 70 percent influenza vaccination rate for children 6 months through 17 years old as part of its Healthy People 2020 objectives, and the Centers for Disease Control and Prevention (CDC), the American Academy of Pediatrics (AAP), as well as the National Heart, Lung, and Blood Institute (NHLBI) recommend that children with SCD receive an annual influenza vaccine.6, 16–18 Despite the risk influenza poses to pediatric patients with SCD, most previous studies have shown that influenza vaccination rates are below the Healthy People 2020 target among individuals with SCD (8%−76%, Table 4). Boston Medical Center (BMC) is an urban, safety net hospital that has been able to attain a high influenza vaccination rate among pediatric SCD patients (e.g. 90.42%% vaccination rate for SCD patients 6 months to 21 years for the 2013–2014 influenza season).19 The current study aims to determine whether the previously reported high influenza vaccination rates have been maintained over time at BMC and whether the high influenza vaccination rates have led to improvement in outcomes (influenza-positive rate and IRH rate). It was hypothesized that BMC’s high influenza vaccination rates have been maintained, and as a result BMC’s rate of influenza cases and influenza-related hospitalizations would be lower than those reported previously in other sources.
Table 4.
Comparison of current study results to previous research regarding influenza vaccination rates, influenza-related hospitalizations, and influenza-positive rates. CI is confidence interval; SCD, sickle cell disease; BMC, Boston Medical Center; EHR, electronic health record.
| Population | Age range | Rate | Data source | Study year(s) | |
|---|---|---|---|---|---|
| Influenza vaccination rate | BMC pediatric SCD patients | 1–17 years | 90.32% | EHR-based SCD registry | 2019–2020 |
| BMC pediatric SCD patients19 | 6 months–21 years | 44.91% | EHR-based SCD registry | 2011–2012 | |
| BMC pediatric SCD patients19 | 6 months–21 years | 80.49% | EHR-based SCD registry | 2012–2013 | |
| BMC pediatric SCD patients19 | 6 months–21 years | 90.42% | EHR-based SCD registry | 2013–2014 | |
| Individuals with asthma in the US20 | 0–17 years | 63.70% (95% CI: 60.6%−66.7%) | Survey of parents | 2012–2014 | |
| General US population21 | 6 months – 17 years | 62.60% (95% CI: 61.9%−63.3%) | Survey of household adults/parents | 2018–2019 | |
| Pediatric SCD patients22 | 6 months – 17 years | 43% (No CI provided) | Medical records | 2000–2001 | |
| Pediatric SCD patients22 | 6 months – 17 years | 76% (No CI provided) | Medical records | 2005–2006 | |
| Pediatric SCD patients7 | 2–5 years | 41% (No CI provided) | Maryland Medicaid claims data | 2002–2008 | |
| Pediatric SCD patients23 | 4 months – 15 years | 8% (No CI provided) | Hospital notes and local general practitioners | 2007–2008 | |
| Pediatric asthma patients24 | 2–14 years | 62.04% (No CI provided) | Prospective nonrandomized controlled trial | 1992–1993 | |
| Children with SCD25 | 6 months - unspecified | ≈45%−55% (No CI provided) | Survey of parents/caregivers | 2011–2012 | |
| Children with asthma25 | 6 months-unspecified | ≈55–65% (No CI provided) | Survey of parents/caregivers | 2011–2012 | |
| Influenza-related hospitalizations | BMC pediatric SCD patients | 1–17 years | 0 | EHR-based SCD registry | 2019–2020 |
| Pediatric asthma patients13 | 6 – 59 months | 1.00 (95% CI: 0.30–1.80) case per 1,000 children | Prospective, population-based study | 2000–2004 | |
| Pediatric SCD patients10 | 0–17 years | 11.20 per 1,000 children (No CI provided) | Healthcare Cost and Utilization Project (HCUP) State Inpatient Databases (SIDs) | 2003–2005 | |
| General population26 | 5–17 years | 0.41 per 1,000 population (No CI provided) | Influenza Hospitalization Surveillance Network (FluSurv-NET) data | 2019–2020 | |
| General population27 | 7–11 years | 0.23 (95% CI:0.185–0.277) per 1,000 children | Healthcare Cost and Utilization Project (HCUP) State Inpatient Databases (SIDs) | 2003–2010 | |
| Pediatric asthma patients27 | 7–11 years | 0.073 (95% CI:0.045 – 0.102) per 1,000 children | Healthcare Cost and Utilization Project (HCUP) State Inpatient Databases (SIDs) | 2003–2010 | |
| Influenza-positive rates | BMC pediatric SCD patients | 1–17 years | 4.84% | EHR-based SCD registry | 2019–2020 |
| SCD patients28 | 6 months – 21 years | 29.60% (No CI provided) | Children’s Healthcare of Atlanta Sickle Cell Disease Clinical Database (SCDCD) | 2012–2017 | |
| General population29 | 0–17 years | 9.30% (95% CI, 8.20% – 11.10%) | Influenza Hospitalization Surveillance Network (FluSurv-NET) with additional calculations | 2010–2016 | |
| Pediatric asthma patients24 | 2–14 years | 52.55% (No CI provided) | Prospective nonrandomized controlled trial | 1992–1993 |
MATERIALS AND METHODS
This study was a retrospective chart review determined to be exempt from Institutional Review Board (IRB) review. The inclusion criteria for this study was a diagnosis of SCD and age of six months to 18 years. Influenza season was defined as ranging from September 1, 2019 through May 30, 2020. Age, sex, SCD genotype, influenza vaccination status for the 2019–2020 influenza season, positive test results for influenza, hospitalization for influenza, and presence of asthma for each of our subjects was ascertained from an electronic health record (EHR)-based SCD registry for pediatric patients with SCD at Boston Medical Center. This registry was created in 2012 for quality improvement and case management purposes.30
BMC uses a multipronged strategy to vaccinate pediatric patients with SCD. The staff at BMC utilize an EHR-based SCD registry that consists of a central data warehouse, a registry management form, and forms for documentations at clinic visits. The forms include information such as SCD genotype, immunization status (for influenza, meningococcal, and pneumococcal vaccines), medications, and laboratory results. The registry management form enables the quality improvement team to add new patients and remove inactive patients.30 The data warehouse produces a report that includes the names, vaccination date, and phone number of patients with SCD every month. A patient navigator uses these reports to determine the recorded immunization status of patients with SCD. They then contact the families of patients who have no recorded influenza vaccination and help them schedule a visit to get vaccinated at the most convenient location. If the patients have in fact been vaccinated elsewhere, the patient navigator collects written confirmation that the patient was vaccinated on the claimed date and the EHR is updated accordingly. Finally, educational materials encouraging influenza vaccination for pediatric patients with SCD are distributed to primary care providers, patients, and families. The methods of distribution are email, postal mail, the clinic’s Facebook page, and by handing them out during hematology clinic visits.19
In order to compare the influenza vaccination rate, IRH rate, and influenza-positive rate with results from other studies, a literature review was conducted. The literature review included studies among pediatric patients with SCD, asthma, and children from the general population. This literature review involved a thorough search using the keywords “influenza”, “asthma”, “sickle cell disease”, “influenza vaccination rate”, “influenza-related hospitalization”, and “influenza-positive”. A total of 14 studies were found that included influenza vaccination rates, IRH rates, and/or influenza-positive rates from the relevant populations. One of the previous studies19 reviewed was conducted at BMC, while the others were not. Studies regarding patients with asthma were included as asthma is associated with greater IRH rates in children and often co-occurs with SCD.11,13
Statistical Methods
Descriptive statistics were used to generate the influenza vaccination rate and influenza-positive rate. Specifically, the influenza vaccination rate was determined by dividing the number of vaccinated subjects by the total number of subjects. The influenza-positive rate was calculated by dividing the number of influenza cases by the total number of subjects. The mean age and standard deviation for age were calculated for subjects with influenza, subjects without influenza, vaccinated subjects, unvaccinated subjects, and all subjects. Fisher’s exact test was utilized to determine if there were any significant differences between the subjects with influenza and subjects without influenza, as well as between vaccinated and unvaccinated subjects with regards to prevalence of asthma, sex, or sickle cell genotype. The independent samples t-test was used to determine if the difference in mean age between subjects with and without influenza as well as between unvaccinated and vaccinated subjects was significant.
RESULTS
Data from 124 patients were included in this study, all of whom were at least six months old by September 1, 2019 and were less than 18 years old by the end of May 2020. This sample was inclusive of all SCD patients eligible for vaccination who seek care at this site. The mean age was 9.77 years. A total of 112 (90.32%) patients were vaccinated for influenza in the 2019–2020 season. Only six (4.84%) patients tested positive for influenza. A total of 28 subjects (22.58%) had a co-occurring diagnosis of asthma and 50.81% of subjects were female (Table 1). There were no influenza-related hospitalizations during the study period (Table 2). There were no statistically significant differences between the subjects with influenza and those without influenza with regards to SCD genotype, sex, number of vaccinated subjects, and number of subjects with asthma. The only statistically significant difference between unvaccinated and vaccinated subjects was in the proportion of subjects with genotype HbS/B+thal (p = 0.02, Table 3).
Table 1.
Characteristics of subjects.
| Attributes | Total | Patients with influenza | Patients without influenza | p-value |
|---|---|---|---|---|
| Number of subjects (%) | 124 | 6 (4.84) | 118 (95.16) | N/A |
| Subjects with asthma (%) | 28 (22.58) | 3 (50) | 25 (21.19) | 0.13 |
| Mean age (years) | 9.77 | 4.67 | 10.03 | 0.005 |
| Standard deviation for age | 4.81 | 2.88 | 4.75 | N/A |
| Female subjects (%) | 63 (50.81) | 3 (50) | 60 (50.85) | 1 |
| Genotype HbSC (%) | 36 (29.03) | 1 (16.67) | 35 (29.66) | 0.67 |
| Genotype HbS/B+thal (%) | 7 (5.65) | 0 (0) | 7 (5.93) | 1 |
| Genotype HbS/Other (%) | 1 (0.81) | 0 (0) | 1 (0.85) | 1 |
| Genotype HbSS or HbS/BOthal (%) | 80 (64.52) | 5 (83.33) | 75 (63.56) | 0.42 |
| Influenza A (%) | 3 (2.42) | 3 (50) | 0 (0) | N/A |
| Influenza B (%) | 3 (2.42) | 3 (50) | 0 (0) | N/A |
| Vaccinated subjects (%) | 112 (90.32) | 6 (100) | 106 (89.83) | 1 |
Table 2.
Health outcomes of subjects.
| n | Percent | |
|---|---|---|
| Subjects with influenza vaccination for 2019–2020 flu season | 112 | 90.32 |
| Confirmed influenza cases | 6 | 4.84 |
| Influenza-related hospitalizations | 0 | 0 |
Table 3.
Comparisons between unvaccinated and vaccinated subjects.
| Attributes | Total | Unvaccinated | Vaccinated | p-value |
|---|---|---|---|---|
| Number of subjects (%) | 124 | 12 | 112 | N/A |
| Subjects with asthma (%) | 28 (22.58) | 3 (25.00) | 25 (22.32) | 0.73 |
| Mean age (years) | 9.77 | 9.00 | 9.86 | 0.58 |
| Standard deviation for age | 4.81 | 5.05 | 4.80 | N/A |
| Female subjects (%) | 63 (50.81) | 7 (58.33) | 56 (50) | 0.76 |
| Genotype HbSC (%) | 36 (29.03) | 4 (33.33) | 32 (28.57) | 0.74 |
| Genotype HbS/B+thal (%) | 7 (5.65) | 3 (25.00) | 4 (3.57) | 0.02 |
| Genotype HbS/Other (%) | 1 (0.81) | 0 (0) | 1 (0.89) | 1 |
| Genotype HbSS or HbS/BOthal (%) | 80 (64.52) | 5 (41.67) | 75 (66.96) | 0.11 |
| Influenza (%) | 6 (4.84) | 0 (0) | 6 (5.36) | 1 |
Patients with influenza were significantly younger than those without influenza (4.67 vs 10.03 years, p=0.005, Table 1). The influenza vaccination rate for pediatric patients with SCD at BMC was higher than the vaccination rates in previous studies outside of BMC,7, 20–25 while the IRH rate10, 13, 26, 27 and the influenza-positive rate,24,28,29 for the pediatric patients with SCD were lower than the previous rates in the literature (Table 4).
DISCUSSION
Our study shows that BMC achieved a high influenza vaccination rate of 90.32% for pediatric patients with SCD. This rate exceeds the Healthy People 2020 target of 70% for children aged 6 months through 17 years old,18 as well as influenza vaccination rates for the general population, pediatric patients with SCD, and children with asthma that were reported in other studies conducted outside of BMC (8%−76%, Table 4). BMC previously attained high vaccination rates in patients 6 months to 21 years of 80.49% and 90.42% for the 2012–13 influenza season and 2013–2014 influenza season respectively.19 The current study demonstrates the ability to maintain a high vaccination rate in pediatric patients with SCD over time without any additional staff since the time the vaccination strategy was first implemented.
The influenza-related hospitalization rate for BMC was lower than any other study, with zero hospitalizations (other IRH rates were 11.20 per 1,000 children for pediatric patients with SCD, 1 case per 1,000 children for children with asthma, and 0.41 per 1,000 children for the general population).10, 13, 26, 27 The previous study that examined IRH rates in children with SCD did not include vaccination rates specifically for children with SCD.10. However, the study did include vaccination rates for children with high-risk conditions, which were relatively low (e.g. 42% for children aged 2–17 years with high-risk conditions in the 2003–4 influenza season).10 Assuming that the vaccination rate for children with SCD was similar to children with other high-risk conditions, this further strengthens the argument that BMC’s IRH rate of zero is due to a high influenza vaccination rate.
The influenza-positive rate for pediatric patients with SCD at BMC was also lower than all other studies (influenza-positive rates were 29.60% for patients with SCD, 9.30% for the general population, and 52.55% for pediatric patients with asthma).24,28,29 All of the patients who contracted influenza were already vaccinated. This is likely reflective of the fact that relatively few patients were unvaccinated. However, the IRH rate was still zero and is likely indicative of influenza vaccination reducing severe illness. This suggests that Boston Medical Center’s strategy to attain high influenza vaccination rates in its pediatric SCD patients has resulted in an improvement in health outcomes. This improvement in outcomes was likely mediated via influenza vaccination preventing patients from being infected as well as reducing illness severity in infected patients. The lower IRH rate at BMC is significant as a previous study that reviewed IRH data in four states concluded that if pediatric patients with SCD had IRH rates equivalent to children without SCD, there would be $1.9 million less hospital charges.10 Thus, BMC’s influenza vaccination strategy has likely reduced economic costs for both the hospital and patients. If other hospitals were to adopt this vaccination strategy, they would likely see a reduction in costs associated with influenza-related hospitalizations.
This study has several limitations. It is possible that patients may have had influenza, but were diagnosed elsewhere. It is also possible that patients might have had influenza, but did not seek medical treatment. However, if patients did not seek medical treatment this may be a sign that they only developed mild illness. Developing only mild illness due to influenza could be a sign of vaccine effectiveness. Finally, this study was only a single-center study.
It is possible that the COVID-19 pandemic may have influenced the results of this study. For example, a statewide stay at home advisory went into effect on March 24, 2020 before being replaced with a slightly less stringent “safer at home” advisory in May.30, 31 A statewide mask mandate also went into effect on May 6, 2020, although numerous communities in Massachusetts implemented local mask mandates prior to this date.32 This is relevant as previous research has found that influenza activity declined after implementation of measures to reduce the spread of COVID-19.33 It is also possible that patients with influenza may have chosen not to seek medical treatment or get tested due to fear of contracting COVID-19 by interacting with others. While any effect of the COVID-19 pandemic would be limited to the last three months of this study, the possibility that the pandemic may have ultimately influenced the results cannot be ruled out.
This study indicates that it is possible to attain a high influenza vaccination rate in a vulnerable population at a safety net hospital and maintain said vaccination rate over a span of multiple years. Other hospitals may benefit from adopting a similar influenza vaccination strategy for pediatric SCD patients and other vulnerable patient populations. They can create their own EHR-based registry that includes immunization status for each patient and that lists the immunizations suggested for patients with SCD.34 It has previously been suggested that community health workers (CHWs) may assist patients with SCD by helping with medication adherence, providing education regarding management of SCD, and performing home visits among other duties.35 In addition to these tasks, other hospitals could benefit by using CHWs to educate patients with SCD and their families about the importance of influenza vaccination. CHWs can also act as patient navigators to schedule vaccinations for pediatric patients with SCD. Hospitals can also simply have nurses or other staff carry out the responsibilities of a patient navigator, thus obviating the need for hiring any additional staff. Hospitals may also implement less labor-intensive methods of reaching patients, such as automated text messages and automated phone calls that can remind patients with no recorded influenza immunizations to get vaccinated. Patient portals may also be used to reach out and remind patients to get vaccinated. In order to determine the applicability of this study’s findings to other hospitals, a multi-center study should be conducted among hospitals that adopt BMC’s influenza vaccination strategy.
This study’s results are especially critical in light of the current COVID-19 pandemic. Specifically, concerns have been raised that overlap between the COVID-19 pandemic and the 2020–2021 flu season may place pressure on hospitals in terms of availability of hospital beds.36 As such, improving influenza vaccination rates can play a crucial role in reducing the burden on hospitals and ensuring that enough hospital beds are available for patients. In response to the COVID-19 pandemic, BMC is using a mobile van so that pediatric patients can be vaccinated right outside their homes.37 Finally, Boston Medical Center’s influenza vaccination strategy can be utilized for other vaccines, including the currently available COVID-19 vaccines.
Acknowledgments
Dr. Sobota is funded by NHLBI grant 1K23HL135436-01
References:
- 1.Kato GJ, Piel FB, Reid CD, et al. Sickle cell disease. Nat Rev Dis Primers. 2018;4:18010. [DOI] [PubMed] [Google Scholar]
- 2.Hassell KL. Population estimates of sickle cell disease in the U.S. Am J Prev Med. 2010;38:S512–S521. [DOI] [PubMed] [Google Scholar]
- 3.Farooq S, Omar MA, Salzman GA. Acute chest syndrome in sickle cell disease. Hosp Pract (1995). 2018;46:144–151. [DOI] [PubMed] [Google Scholar]
- 4.Platt OS, Brambilla DJ, Rosse WF, et al. Mortality in sickle cell disease -- life expectancy and risk factors for early death. N Engl J Med. 1994;330:1639–1644. [DOI] [PubMed] [Google Scholar]
- 5.Miller AC, Gladwin MT. Pulmonary complications of sickle cell disease. Am J Respir Crit Care Med. 2012;185:1154–1165. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 6.American Academy of Pediatrics Committee on Infectious Diseases. Recommendations for prevention and control of influenza in children, 2019–2020. Pediatrics. 2019;144:e20192478. [DOI] [PubMed] [Google Scholar]
- 7.Bundy DG, Muschelli J, Clemens GD, et al. Preventive care delivery to young children with sickle cell disease. J Pediatr Hematol Oncol. 2016;38:294–300. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 8.Vichinsky EP, Neumayr LD, Earles AN, et al. Causes and outcomes of the acute chest syndrome in sickle cell disease. National Acute Chest Syndrome Study Group. N Engl J Med. 2000;342:1855–1865. [DOI] [PubMed] [Google Scholar]
- 9.Strouse JJ, Reller ME, Bundy DG, et al. Severe pandemic H1N1 and seasonal influenza in children and young adults with sickle cell disease. Blood. 2010;116:3431–3434. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 10.Bundy DG, Strouse JJ, Casella JF, et al. Burden of influenza-related hospitalizations among children with sickle cell disease. Pediatrics. 2010;125:234–243. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 11.Morris CR. Asthma management: Reinventing the wheel in sickle cell disease. Am J Hematol. 2009;84:234–241. [DOI] [PubMed] [Google Scholar]
- 12.Cohen RT, Klings ES, Strunk RC. Sickle cell disease: Wheeze or asthma?. Asthma Res Pract. 2015;1:14. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 13.Miller EK, Griffin MR, Edwards KM, et al. Influenza burden for children with asthma. Pediatrics. 2008;121:1‐8. [DOI] [PubMed] [Google Scholar]
- 14.Schwarze J, Openshaw P, Jha A, et al. Influenza burden, prevention, and treatment in asthma‐A scoping review by the EAACI influenza in asthma task force. Allergy. 2018;73:1151–1181. [DOI] [PubMed] [Google Scholar]
- 15.Merckx J, Ducharme FM, Martineau C, et al. Respiratory viruses and treatment failure in children with asthma exacerbation. Pediatrics. 2018;142:e20174105. [DOI] [PubMed] [Google Scholar]
- 16.Centers for Disease Control and Prevention (CDC). Infections and sickle cell disease 5 tips to help prevent infections [CDC Web site]. October 21, 2019. Available at: https://www.cdc.gov/ncbddd/sicklecell/healthyliving-prevent-infection.html. Accessed May 18, 2020.
- 17.National Heart, Lung, and Blood Institute. The management of sickle cell disease [NHLBI Web site]. June 2002. Available at: http://www.nhlbi.nih.gov/health/prof/blood/sickle/sc_mngt.pdf. Accessed August 22, 2020.
- 18.U.S. Department of Health and Human Services. Immunization and infectious diseases [Healthy People Web site]. July 29, 2020. Available at: https://www.healthypeople.gov/2020/topics-objectives/topic/immunization-and-infectious-diseases/objectives. Accessed July 29, 2020.
- 19.Sobota AE, Kavanagh PL, Adams WG, et al. Improvement in influenza vaccination rates in a pediatric sickle cell disease clinic. Pediatr Blood Cancer. 2014;62:654–657. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 20.Centers for Disease Control and Prevention (CDC). Flu vaccination among children with current asthma [CDC Web site]. December 29, 2017. Available at: https://www.cdc.gov/asthma/asthma_stats/documents/AsthmaStats_Asthma_Flu_Vaccination_Children_PDF_Final2-508.pdf. Accessed June 15, 2020.
- 21.Centers for Disease Control and Prevention (CDC). Flu vaccination coverage, United States, 2018–19 influenza season [CDC Web site]. September 26, 2019. Available at: https://www.cdc.gov/flu/fluvaxview/coverage-1819estimates.htm. Accessed June 14, 2020.
- 22.Hambidge SJ, Ross C, Glanz J, et al. Trivalent inactivated influenza vaccine is not associated with sickle cell crises in children. Pediatrics. 2011;129:e54–e59. [DOI] [PubMed] [Google Scholar]
- 23.Howard-Jones M, Randall L, Bailey-Squire B, et al. An audit of immunisation status of sickle cell patients in Coventry, UK. J Clin Pathol. 2008;62:42–45. [DOI] [PubMed] [Google Scholar]
- 24.Sugaya N, Nerome K, Ishida M, et al. Efficacy of inactivated vaccine in preventing antigenically drifted influenza type A and well-matched type B. JAMA. 1994;272:1122–1126. [PubMed] [Google Scholar]
- 25.Centers for Disease Control and Prevention (CDC). Influenza vaccination practices of physicians and caregivers of children with neurologic and neurodevelopmental conditions—United States, 2011–12 influenza season. MMWR Morb Mortal Wkly Rep. 2013;62:744–746. [PMC free article] [PubMed] [Google Scholar]
- 26.Centers for Disease Control and Prevention (CDC). Laboratory-confirmed influenza hospitalizations [CDC Web site]. October 31, 2020. Available at: https://gis.cdc.gov/GRASP/Fluview/FluHospRates.html. Accessed January 26, 2021.
- 27.Goldstein E, Finelli L, O’Halloran A, et al. Hospitalizations associated with respiratory syncytial virus and influenza in children, including children diagnosed with asthma. Epidemiology. 2019;30:918–926. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 28.Kao CM, Lai K, Mcateer JM, et al. Influenza vaccine effectiveness and disease burden in children and adolescents with sickle cell disease: 2012‐2017. Pediatr Blood Cancer. 2020;67:e28358. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 29.Tokars JI, Olsen SJ, Reed C. Seasonal incidence of symptomatic influenza in the United States. Clin Infect Dis. 2018;66:1511–1518. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 30.Jarmanning A Baker orders all non-essential Mass. businesses to close starting Tuesday [WBUR web site]. March 23, 2020. Available at: https://www.wbur.org/commonhealth/2020/03/23/baker-closes-businesses-coronavirus. Accessed March 13, 2021.
- 31.CBS Boston. Here’s how Massachusetts will reopen under Governor Charlie Baker’s plan [CBS Boston web site]. May 18, 2020. Available at: https://boston.cbslocal.com/2020/05/18/massachusetts-reopening-plan-governor-charlie-baker-press-conference-update-businesses-list/. Accessed March 13, 2021.
- 32.Ruckstuhl L Mass. cities and towns that now require face masks, coverings in public [WBUR web site]. May 6, 2020. Available at: https://www.wbur.org/commonhealth/2020/04/29/face-masks-covering-orders-coronavirus-massachusetts. Accessed March 13, 2021.
- 33.Olsen SJ, Azziz-Baumgartner E, Budd AP, et al. Decreased influenza activity during the COVID-19 pandemic — United States, Australia, Chile, and South Africa, 2020. MMWR Morb Mortal Wkly Rep. 2020;69:1305–1309. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 34.Kavanagh PL, Sobota AE, McClure ES, et al. Using an electronic health record‐based registry to improve pediatric sickle cell care. J Clin Outcomes Manag. 2014;21:159. [Google Scholar]
- 35.Hsu LL, Green NS, Ivy ED, et al. Community health workers as support for sickle cell care. Am J Prev Med. 2016;51:S87–S98. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 36.Belongia EA, Osterholm MT. COVID-19 and flu, a perfect storm. Science. 2020;368:1163. [DOI] [PubMed] [Google Scholar]
- 37.Bailey M Mobile medicine: How a pediatric vaccination van has upended the idea of care [Boston Medical Center Web site]. June 9, 2020. Available at: https://www.bmc.org/healthcity/population-health/how-pediatric-vaccination-van-has-upended-idea-care. Accessed September 7, 2020.