"Health system approach" for improving immunization program performance

Developing a roadmap to reach and sustain 90% full immunization coverage through a cross-sectoral system strengthening strategy in Bihar, India

INTRODUCTION

Reducing childhood mortality by curtailing the incidence of vaccine preventable diseases is contingent upon a robust and high-performing routine immunization system. According to the available data, the full immunization coverage (FIC) in the state of Bihar (India) has reached ~ 71%. While the government aspires to reach 90% FIC, a systematic evidence-based investigation of the reasons behind underimmunization as well as the identification of drivers and enablers to reach and sustain 90% FIC is critical. This study aimed to review the factors leading to underimmunized children in the state of Bihar and develop a forward-looking roadmap to reach and sustain 90% FIC by adopting a system strengthening approach.

METHOD

We conducted a desk review, followed by extensive stakeholder interviews and field visits to document and analyze the data and evidence relevant to routine immunization system performance in the state of Bihar. The stakeholders included the State Immunization Officer, District Immunization Officers, Block-level health officials, representatives from development agencies, healthcare workers, and caregivers. A total of eighty-six structured interviews were conducted, which included qualitative and quantitative parameters.

RESULT

While positive results were observed from the assessment of Bihar's immunization system, the implementation of targeted strategies for supply, service delivery and demand can provide a means to achieve FIC of 90%. The roadmap developed by the Government of Bihar enlists 40 + interventions across key thematic areas and has been prioritized over a 5-year time horizon as short, medium, and long-term milestones to achieve 90% FIC. These interventions include strengthening the data availability and quality, improving the governance and review mechanism, augmenting the capacity of health workers involve with immunization programme, and initiatives to increase demand for immunization services.

CONCLUSION

The Bihar's Immunization Roadmap development project work follows a methodical approach to assess and identify intervention to improve immunization coverage and can provide information and reference to other states and countries that are aiming to formulate similar action plans.

Effect of rotavirus vaccination on the burden of rotavirus disease and associated antibiotic use in India: A dynamic agent-based simulation analysis

BACKGROUND

Rotavirus is a leading cause of diarrhea in infants and young children in many low- and middle-income countries. India launched a childhood immunization program for rotavirus in 2016, starting with four states and expanding it to cover all states by 2019. The objective of this study was to estimate the effects of the rotavirus vaccination program in India on disease burden and antibiotic misuse.

METHODS

We built a dynamic agent-based model of rotavirus progression in children under five within each district in India. Simulations were run for various scenarios of vaccination coverage in the context of India's Universal Immunization Programme. Population data were obtained from the National Family Household Surveys and used to calibrate the models. Disease parameters were obtained from published studies. We estimated past and projected future reduction of disease burden and antibiotic misuse due to full vaccination nationwide, by state, and by wealth quintile.

RESULTS

We estimate that rotavirus vaccination in India has reduced the prevalence of rotavirus cases by 33.7% (prediction interval: 30.7-36.0%), total antibiotic misuse due to rotavirus by 21.8% (18.6-25.1%), and total deaths due to rotavirus by 38.3% (31.3-44.4%) for children under five. We estimate total antibiotic misuse due to rotavirus infection to be 7.6% (7.5-7.9%) of total antibiotic consumption in this demographic versus 9.6% (9.4-9.9%) in the absence of vaccination. We project rotaviral prevalence to drop to below one case for every 100,000 individuals in those below five if vaccination coverage is increased by 50.3% (45.2-58.5%) to 68.1% (63.1-76.4) nationwide.

CONCLUSION

Universal coverage of childhood rotavirus vaccination can substantially reduce inappropriate antibiotic use in India.

Analyzing the vaccination debate in social media data Pre- and Post-COVID-19 pandemic

The COVID-19 virus has caused and continues to cause unprecedented impacts on the life trajectories of millions of people globally. Recently, to combat the transmission of the virus, vaccination campaigns around the world have become prevalent. However, while many see such campaigns as positive (e.g., protecting lives), others see them as negative (e.g., the side effects that are not fully understood scientifically), resulting in diverse sentiments towards vaccination campaigns. In addition, the diverse sentiments have seldom been systematically quantified let alone their dynamic changes over space and time. To shed light on this issue, we propose an approach to analyze vaccine sentiments in space and time by using supervised machine learning combined with word embedding techniques. Taking the United States as a test case, we utilize a Twitter dataset (approximately 11.7 million tweets) from January 2015 to July 2021 and measure and map vaccine sentiments (Pro-vaccine, Anti-vaccine, and Neutral) across the nation. In doing so, we can capture the heterogeneous public opinions within social media discussions regarding vaccination among states. Results show how positive sentiment in social media has a strong correlation with the actual vaccinated population. Furthermore, we introduce a simple ratio between Anti and Pro-vaccine as a proxy to quantify vaccine hesitancy and show how our results align with other traditional survey approaches. The proposed approach illustrates the potential to monitor the dynamics of vaccine opinion distribution online, which we hope, can be helpful to explain vaccination rates for the ongoing COVID-19 pandemic.

Impact of health system strengthening on delivery strategies to improve child immunisation coverage and inequalities in rural Madagascar

Background

To reach global immunisation goals, national programmes need to balance routine immunisation at health facilities with vaccination campaigns and other outreach activities (eg, vaccination weeks), which boost coverage at particular times and help reduce geographical inequalities. However, where routine immunisation is weak, an over-reliance on vaccination campaigns may lead to heterogeneous coverage. Here, we assessed the impact of a health system strengthening (HSS) intervention on the relative contribution of routine immunisation and outreach activities to reach immunisation goals in rural Madagascar.

Methods

We obtained data from health centres in Ifanadiana district on the monthly number of recommended vaccines (BCG, measles, diphtheria, tetanus and pertussis (DTP) and polio) delivered to children, during 2014–2018. We also analysed data from a district-representative cohort carried out every 2 years in over 1500 households in 2014–2018. We compared changes inside and outside the HSS catchment in the delivery of recommended vaccines, population-level vaccination coverage, geographical and economic inequalities in coverage, and timeliness of vaccination. The impact of HSS was quantified via mixed-effects logistic regressions.

Results

The HSS intervention was associated with a significant increase in immunisation rates (OR between 1.22 for measles and 1.49 for DTP), which diminished over time. Outreach activities were associated with a doubling in immunisation rates, but their effect was smaller in the HSS catchment. Analysis of cohort data revealed that HSS was associated with higher vaccination coverage (OR between 1.18 per year of HSS for measles and 1.43 for BCG), a reduction in economic inequality, and a higher proportion of timely vaccinations. Yet, the lower contribution of outreach activities in the HSS catchment was associated with persistent inequalities in geographical coverage, which prevented achieving international coverage targets.

Conclusion

Investment in stronger primary care systems can improve vaccination coverage, reduce inequalities and improve the timeliness of vaccination via increases in routine immunisations.

Predictors of Adherence to Routine Immunization Schedule Among Caretakers of Children Aged 10 to 18 Months in Lira City, Uganda

Background

Although the majority of nations have routine immunization programs in place as a public health strategy, more than 1.5 million children under the age of 5 die yearly worldwide due to inadequate vaccination coverage. This study investigated the predictors of adherence to routine immunization schedules in Lira city.

Methods

This was a cross-sectional study among 420 caretakers of children aged 10 to 18 months. Bivariate and multiple regression analyses were conducted to assess the predictors of adherence to the full immunization schedule. A P-value > .05 was considered statistically significant at 95% CI.

Results

The study result indicated that the majority, 237 (56.4%) of caretakers were aged 25 to 34 years, 205 (48.8%) had attained primary level education, and 284 (67.6%) were married. The results showed that 365 (87.0%) had their children fully immunized. The predictors of adherence to full immunization schedule were knowledge on when to start vaccination (AOR:5.65; 95% CI:1.82-17.55; P = .003), maternal outcome expectations (AOR:3.45; 95% CI:1.16-10.29; P = .03) and maternal knowledge (AOR:2.15; 95% CI:1.18-3.90; P = .01).

Conclusion

The study findings show that 9 in 10 of the caregivers adhered to the immunization schedule. The significant predictors of adherence to full immunization were flexible clinical hours, maternal outcome expectations and maternal knowledge. Based on the conclusions we recommend that government and service providers be flexible in clinic hours and continue health education to women of childbearing age at an early stage, especially during antenatal care visits, delivery and the postnatal period on childhood vaccination to maintain adherence to the routine immunization schedule.

Improving vaccination coverage and timeliness through periodic intensification of routine immunization: evidence from Mission Indradhanush

Only an estimated 62% of Indian children under the age of 2 years are fully immunized. We examined the association between India's Mission Indradhanush (MI)-a periodic intensification of the routine immunization program-which was implemented in phases across districts between March 2015 and July 2017, and routine vaccination coverage and timeliness among children. We used data from a 2015 to 2016 national survey of children (n = 29,532) and employed difference-in-difference regressions to examine binary indicators of receipt of 11 vaccines and whether vaccines were received at recommended ages. The full immunization rate was 27% higher among children under 2 years old residing in MI phase 1 and 2 districts (intervention group) as compared with those residing elsewhere (control group). The rate of receiving all vaccines at recommended ages was 8% higher in the intervention group. Receiving doses of oral polio vaccine (OPV) birth dose, OPV dose 1 (OPV1), OPV2, OPV3, bacillus Calmette-Guérin, and hepatitis B birth dose vaccines were 9%, 9%, 11%, 16%, 5%, and 19% higher in the intervention group than the control group, respectively. More research is required on the cost-effectiveness of investing in MI-type programs as compared with routine immunization.

Barriers and strategies in developing an integrated immunization stewardship program in the health-system setting: The role of the pharmacist

In an effort to expedite the publication of articles related to the COVID-19 pandemic, AJHP is posting these manuscripts online as soon as possible after acceptance. Accepted manuscripts have been peer-reviewed and copyedited, but are posted online before technical formatting and author proofing. These manuscripts are not the final version of record and will be replaced with the final article (formatted per AJHP style and proofed by the authors) at a later time.

Modeling of Vaccination and Contact Tracing as Tools to Control the COVID-19 Outbreak in Spain

We developed an agent-based stochastic model, based on P Systems methodology, to decipher the effects of vaccination and contact tracing on the control of COVID-19 outbreak at population level under different control measures (social distancing, mask wearing and hand hygiene) and epidemiological scenarios. Our findings suggest that without the application of protection social measures, 56.1% of the Spanish population would contract the disease with a mortality of 0.4%. Assuming that 20% of the population was protected by vaccination by the end of the summer of 2021, it would be expected that 45% of the population would contract the disease and 0.3% of the population would die. However, both of these percentages are significantly lower when social measures were adopted, being the best results when social measures are in place and 40% of contacts traced. Our model shows that if 40% of the population can be vaccinated, even without social control measures, the percentage of people who die or recover from infection would fall from 0.41% and 56.1% to 0.16% and 33.5%, respectively compared with an unvaccinated population. When social control measures were applied in concert with vaccination the percentage of people who die or recover from infection diminishes until 0.10% and 14.5%, after vaccinating 40% of the population. Vaccination alone can be crucial in controlling this disease, but it is necessary to vaccinate a significant part of the population and to back this up with social control measures.

Understanding inequalities in child immunization in India: a decomposition approach

The importance of childhood immunization for healthy child growth and development is well recognized and is considered to be the best and most cost-effective lifesaver. Low socioeconomic status has been shown to be associated with low child immunization and health care utilization, but the inequalities in immunization coverage due to social and economic factors are poorly understood. This study aimed to explore the association between child immunization coverage and various socioeconomic factors and to quantify their contributions to generating inequalities in immunization coverage in India. The study data are from the National Family Health Survey-4 conducted in 2015-16. The association between socioeconomic determinants and child full immunization coverage was estimated using the χ2 test and binary logistic regression. Concentration indices were estimated to measure the magnitude of inequality, and these were further decomposed to explain the contribution of different socioeconomic factors to the total disparity in full immunization coverage. The results showed that the uptake of immunization in 2015-16 was highly associated with mother's educational status and household wealth. The concentration index decomposition revealed that inequality (immunization disadvantage) was highest among poorer economic groups and among children whose mothers were illiterate. The overall concentration index value indicates that the weaker socioeconomic groups in India are more disadvantaged in terms of immunization interventions. The results offer insight into the dynamics of the variation in immunization coverage in India and help identify vulnerable populations that should be targeted to decrease socioeconomic inequalities in the country.

Immunity against diphtheria among children aged 5-17 years in India, 2017-18: a cross-sectional, population-based serosurvey

BACKGROUND

Diphtheria is re-emerging as a public health problem in several Indian states. Most diphtheria cases are among children older than 5 years. In this study, we aimed to estimate age-specific immunity against diphtheria in children aged 5-17 years in India.

METHODS

We used residual serum samples from a cross-sectional, population-based serosurvey for dengue infection done between June 19, 2017, and April 12, 2018, to estimate the age-group-specific seroprevalence of antibodies to diphtheria in children aged 5-17 years in India. 8309 serum samples collected from 240 clusters (122 urban and 118 rural) in 60 selected districts of 15 Indian states spread across all five geographical regions (north, northeast, east, west, and south) of India were tested for the presence of IgG antibodies against diphtheria toxoid using an ELISA. We considered children with antibody concentrations of 0·1 IU/mL or greater as immune, those with levels less than 0·01 IU/mL as non-immune (and hence susceptible to diphtheria), and those with levels in the range of 0·01 to less than 0·1 IU/mL as partially immune. We calculated the weighted proportion of children who were immune, partially immune, and non-immune, with 95% CIs, for each geographical region by age group, sex, and area of residence (urban vs rural).

FINDINGS

29·7% (95% CI 26·3-33·4) of 8309 children aged 5-17 years were immune to diphtheria, 10·5% (8·6-12·8) were non-immune, and 59·8% (56·3-63·1) were partially immune. The proportion of children aged 5-17 years who were non-immune to diphtheria ranged from 6·0% (4·2-8·3) in the south to 16·8% (11·2-24·4) in the northeast. Overall, 9·9% (7·7-12·5) of children residing in rural areas and 13·1% (10·2-16·6) residing in urban areas were non-immune to diphtheria. A higher proportion of girls than boys were non-immune to diphtheria in the northern (17·7% [12·6-24·2] vs 7·1% [4·1-11·9]; p=0·0007) and northeastern regions (20·0% [12·9-29·8] vs 12·9% [8·6-19·0]; p=0·0035).

INTERPRETATION

The findings of our serosurvey indicate that a substantial proportion of children aged 5-17 years were non-immune or partially immune to diphtheria. Transmission of diphtheria is likely to continue in India until the immunity gap is bridged through adequate coverage of primary and booster doses of diphtheria vaccine.

FUNDING

Indian Council of Medical Research.

The child healthcare system in Cyprus

This article describes the child healthcare system in Cyprus up to June 2019. Before that Cyprus used to be the only country in the European Union without a universal National Health System. Up to 2019 child healthcare in Cyprus consisted of two separate sectors: the public and the private system. The public healthcare system is financed by the government, while in the private sector the patients pay themselves or are covered by private insurance. There is easy access to acute medical care in the emergency departments of five public hospitals across the country. However, primary care is not available free-of-charge to all children. Primary healthcare is delivered in the paediatric outpatient departments of various public and private hospitals and clinics, as well as by numerous paediatricians within private practices. Secondary care is provided mainly in the public sector and to a lesser extent in private clinics. Tertiary care is available only centrally in the capital of Cyprus, at a dedicated university-affiliated maternity and children's public hospital with specialist paediatric services. Current major child health challenges in Cyprus include dealing with obesity, mental health, chronic illnesses, and vulnerable groups. However, the basic available health indicators for children show an improving trend over time. A national healthcare system was introduced at the end of 2017 and is expected to remove the inequalities and discrepancies that currently extend over the area of child health by tackling financial, quality, equity, efficiency, and effectiveness issues.

Exploring Strategies to Improve Adherence to Immunization Schedule: A Study among Children Attending Maternal and Child Health Clinic at Kenyatta National Hospital, Nairobi, Kenya

Background

Globally, immunization is among the major contributors to public health, preventing 20% of childhood mortality annually. The highest fatality rates from vaccine preventable diseases are usually among children under five. Despite immunization guidelines put in place by the World Health Organization, globally, 1.5 million children die annually related to inadequate vaccination coverage. Existing literature indicate that there is an increase in nonadherence to immunization schedule in developing countries, and therefore, there is an increased demand to improve adherence to immunization schedule.

Objective

To explore strategies that will improve adherence to immunization schedule among children under 24 months attending the Maternal and Child Health clinic at Kenyatta National Hospital.

Methods

A cross-sectional mixed method study involving caregivers (n = 214) of well babies attending the Maternal and Child Health clinic. Data was collected using semistructured questionnaires, focus group discussions, and key informant interviews and analyzed using SPSS V.20.

Results

There was a significant relationship between the level of education and marital status of the caregivers and adherence to immunization schedule. Barriers found that is related to adherence to immunization schedule included far distance from health facility, baby's sickness, and vaccine stock-outs while employment of a caregiver was a constrainer factor.

Conclusion

The enabling factors to current strategies of improving adherence to immunization schedule were having more health facilities near residential areas, using text messages reminders a day before the clinic date to remind caregivers of the due date for the clinic, and constant availability of vaccines. The health system strategies that would improve adherence to immunization schedules were more flexible clinic hours, availability of vaccines on daily basis, phone call reminders by health care providers, and increasing awareness on the importance of both vaccinations and adherence to immunization schedule.

Adult vaccination in India: status and the way forward

In the last two decades, the childhood vaccination coverage in most low and middle-income countries including India has increased. Additional vaccines are being offered through national immunization programs as well as through private sector and the benefits of vaccination are reaching to more children than ever. This has resulted in major decrease in vaccine preventable diseases and contributed to decline in the morbidity and mortality rates. This development is expected to result in epidemiological transition (which is already happening) and mandates for policies and strategies to extend the benefit of available vaccines and vaccination beyond traditionally target age groups to include the adults, elderly and the at-risk populations. This article reviews the present status of adult vaccination in India and proposes a few approaches to move towards life course vaccination.

On the Design of Hyperstable Feedback Controllers for a Class of Parameterized Nonlinearities. Two Application Examples for Controlling Epidemic Models

This paper studies the hyperstability and the asymptotic hyperstability of a single-input single-output controlled dynamic system whose feed-forward input-output dynamics is nonlinear and eventually time-varying consisting of a linear nominal part, a linear incremental perturbed part and a nonlinear and eventually time-varying one. The nominal linear part is described by a positive real transfer function while the linear perturbation is defined by a stable transfer function. The nonlinear and time-varying disturbance is, in general, unstructured but it is upper-bounded by the combination of three additive absolute terms depending on the input, output and input-output product, respectively. The non-linear time-varying feedback controller is any member belonging to a general class which satisfies an integral Popov's-type inequality. This problem statement allows the study of the conditions guaranteeing the robust stability properties under a variety of the controllers designed for the controlled system and controller disturbances. In this way, set of robust hyperstability and asymptotic hyperstability of the closed-loop system are given based on the fact that the input-output energy of the feed-forward controlled system is positive and bounded for all time and any given initial conditions and controls satisfying Popov's inequality. The importance of those hyperstability and asymptotic hyperstability properties rely on the fact that they are related to global closed-loop stability, or respectively, global closed-loop asymptotic stability of the same uncontrolled feed-forward dynamics subject to a great number of controllers under the only condition that that they satisfy such a Popov's-type inequality. It is well-known the relevance of vaccination and treatment controls for Public Health Management at the levels of prevention and healing. Therefore, two application examples concerning the linearization of known epidemic models and their appropriate vaccination and/or treatment controls on the susceptible and infectious, respectively, are discussed in detail with the main objective in mind of being able of achieving a fast convergence of the state- trajectory solutions to the disease- free equilibrium points under a wide class of control laws under deviations of the equilibrium amounts of such populations.

New vaccine introductions in Africa before and during the decade of vaccines - Are we making progress?

Vaccines are excellent investments with far-reaching rewards beyond individual and population health, but their introduction into national programs has been historically slow in Africa. We provide an overview of the introduction of new and underutilized vaccines in countries of the WHO African Region by 2017, using data from the WHO-UNICEF Joint Reporting Form. By 2017, all 47 countries had introduced vaccines containing hepatitis B (compared to 11% in 2000 and 98% in 2010) and Haemophilus influenzae type b (Hib) (compared to 4% in 2000 and 91% in 2010). The proportion of countries that had introduced other vaccines by 2017 was 83% for pneumococcal conjugate vaccine (PCV) from 7% in 2010, 72% for rotavirus vaccine from 2% in 2010, 55% for the second dose of a measles-containing vaccine (MCV2) (compared to 11% in 2000 and 17% in 2010), and 45% for rubella-containing vaccines (RCV) (compared to 4% in 2000 and 7% in 2010). From 2000 to 2010, there was no significant difference between countries eligible (N = 36) and those not eligible (N = 10) for Gavi support in the introduction of hepatitis B and PCV. However, Gavi eligible countries were more likely to introduce Hib and non-Gavi eligible countries were more likely to introduce MCV2 and RCV. From 2010 to 2017, the only significant differences that remained between the two groups of countries were with mumps, inactivated polio and seasonal influenza vaccines; which non-Gavi eligible countries were more likely to have introduced. There has been significant progress in the introduction of new childhood vaccines in Africa, mostly driven by Gavi support. As many countries are expected to transition out of Gavi support soon, there is need for countries in the region to identify predictable, reliable and sustainable immunization funding mechanisms. This requires commitments and actions that go beyond the purchase of vaccines.

Implementation of "health systems approach" to improve vaccination at birth in institutional deliveries at public health facilities; experience from six states of India

INTRODUCTION

Newborn vaccination is an integral part of routine immunization program in India, but program implementation gaps exist. The focus of this article is to identify and describe an implementation strategy which could improve the newborn vaccination at the facility level.

MATERIALS AND METHODS

A situation analysis was conducted through a mixed-methods approach to identify the lacunae in the health system and the same was used to develop an implementation strategy to improve newborn vaccination coverage across the six priority states.

RESULTS

Issues in stewardship and human resource, vaccine-related stock-outs, and poor service delivery were some of the reasons for low facility-level vaccination coverage. After implementation of a health system-based strategy, the new born vaccination improved from 55% to 88% across 10 quarters of program implementation. Factors such as sensitization of stakeholders, vaccination on holidays, rigorous documentation, and supportive supervision of health staff were primary reasons for improvement in service delivery.

CONCLUSION

Importance of newborn immunization at birth is well established. The results from six states prove that "health systems approach" as an implementation strategy is a viable tool to improve newborn immunization at birth.

Improving immunization practices in United States hospitals and health systems

Purpose

Payment for healthcare services in the USA has shifted from fee for service to compensation based on value and quality. The indicators used for payments are a variety of clinical measures, including administration of vaccines to patients. The purpose of this paper is to describe the implementation of programs in health systems to improve vaccination rates and patient outcomes.

Design/methodology/approach

A search of the literature was conducted to find examples of vaccine programs in US health systems, and also to identify policies to improve immunization rates.

Findings

Successful programs for improving vaccination rates require advocacy and support of leadership, a systematic and multidisciplinary approach, and an evaluation of local resources and capacity. Numerous examples exist of medical, nursing, and pharmacy led programs that improve vaccination rates. The department in charge has relied on the support of other groups to ensure the success.

Social implications

Mandatory vaccination of healthcare personnel (HCP) in the health system has been a growing trend in the USA. Although there has been some resistance to mandatory vaccinations for HCP, the standards and requirements have resulted in improved rates in health systems, which ultimately improve efficiency and protects patients.

Originality/value

This review describes considerations for implementing a successful vaccination program in a health system and provides examples of specific strategies. An overview of mandatory vaccinations for HCP is also described.

Examining the structure and behavior of Afghanistan’s routine childhood immunization system using system dynamics modeling

Purpose

The purpose of this paper is to demonstrate how public health and systems science methods can be combined to examine the structure and behavior of Afghanistan’s routine childhood immunization system to identify the pathways through which health system readiness to deliver vaccination services may extend beyond immunization outcomes.

Design/methodology/approach

Using findings from an ecological study of Afghanistan’s immunization system and a literature review on immunization program delivery, the routine immunization system was mapped using causal loop diagrams. Next, a stock-and-flow diagram was developed and translated to a system dynamics (SD) model for a system-confirmatory exercise. Data are from annual health facility assessments and two cross-sectional household surveys. SD model results were compared with measured readiness and service outcomes to confirm system structure.

Findings

Readiness and demand-side components were associated with improved immunization coverage. The routine immunization system was mapped using four interlinking readiness subsystems. In the SD model, health worker capacity and demand-side factors significantly affected maternal health service coverage. System readiness components affected their future measures mostly negatively, which may indicate that the reinforcing feedback drives current system-structured behavior.

Originality/value

The models developed herein are useful to explore the potential impact of candidate interventions on service outcomes. This paper documents the process through which public health and systems investigators can collaboratively develop models that represent the feedback-driven behavior of health systems. Such models allow for more realistically addressing health policy and systems-level research questions.