Nina H. Fefferman EENR/DIMACS Rutgers University & InForMID Tufts Univ. School of Medicine

1. The Impact of Household Capital Models on Targeted Epidemiological Control Strategies for Diseases with Age-Based Etiologies Nina H. Fefferman EENR/DIMACS Rutgers University & InForMID Tufts Univ. School of Medicine

2. Integrating economics into epidemiology has led to targeted recommendations for treatment to combat epidemics • Decisions using cost-benefit analyses or optimization techniques are based on trying to achieve particular goal: • Minimize deaths • Minimize economic loss (to community or individuals) • Minimize interruption of society/service • Minimize numbers ill (per unit time or overall) • etc. • However, most of these have looked either at individual health choices (made only for yourself), or total communities

3. For total communities: • Normal assumption: limited resources are a “community level problem” • Individuals don’t make decisions, public health officials recommend strategies • Vaccinate children first • Treat elderly first • etc. • Targeted treatment/prophylaxis recommendations are then followed or not, leading to sensitivity studies for “coverage”, “compliance” or “adherence”

4. For individuals: • Normal assumption is behavior is “selfish”, maximizing personal health outcome at a minimum of personal cost • Individuals are usually assumed to be willing to cause public hardship in favor of personal benefit • Tragedy of the Commons • Lemon Paradox • even Prisoner’s Dilemma type things • Investigation then usually examines how the individual behaviors predicted by the models will cause community-level effects (e.g. herd immunity)

5. But do the same recommendations hold for “household economic” decisions? • In practice, economic resources are shared within a family • If recommendations involve “elderly” or “children”, the also involve all the other members of the family • (a little different for nursing homes and orphanages, but still…) • Also, while community-level recommendations can be made, individuals are still potentially paying the costs • If this is done via a tax or community fund, then we’re just fine, but if this is voluntary participation in a public health recommendation, there may be different trade-offs (especially if not mediated by a community physician)

6. What happens when households themselves have limited economic resources? We know that, independent of disease, access to health care and monetary resources themselves increase individual health If illness compromises an individual’s ability to earn money, their future health, independent of the particular illness could also be jeopardized. If the same individual is responsible for supporting dependents, the health of those dependents could also be compromised

7. Does this “dependents” perspective alter our analysis of how best to mitigate risks? • For ease, let’s say that the dynamics of these things are a bit simple: • Lack of resources instantly decreases health, and thereby increases susceptibility to disease • There are only two types of people: producers and consumers • Consumers rely on producers for resources • Producers produce resources for themselves and others • For simplicity, we’ll assume Consumers are children and Producers are adults (e.g. dependent elderly are treated economically AND etiologically like children)

8. Simple daily model of economics Each day starts with “left over” resources, saved from previous days In each household, an average number of Producers gain an average amount of resources for the household In each household, if there are sick people, the household pays up to what they have to treat them according to a public health recommendation (we’ll vary these to see what happens) If there is money left over, then they buy food (shared evenly among all, though maybe not enough)

9. Mostly simple daily SIR disease process: Basic household: Average size of household: and Rates of transmission within household: Rates of transmission within community: When there isn’t enough food, these increase to: and and Natural rates of recovery: Treatment based rates of recovery: . Basic community: Total population size: N

10. So the picture: Lots of “average” households, which together are a community

11. Transmission comes both from within the family and from the community and and

12. We assume that each house really is every house, so there are no differences in either econ or epi between houses and and

13. and Mathy details happen! (details available upon request, but they are somewhat involved)

14. We then model the epidemiological outcome and compare results First, we choose public health strategies: treat everyone uniformly, treat only consumers, treat only producers Next, we model the disease spread without any economic limitation (so no ), and we treat everyone our strategy says we should Lastly, include household economic limitation and try all our strategies again this time using

15. We pick some parameter values (don’t really matter because we hold them constant across models)

16. Epidemic curves when treatment costs don’t impact household health maintenance or susceptibility.

17. Epidemic curves when treatment costs do impact household health maintenance and susceptibility

18. Comparison of Outcomes: Without Econ Constraint With Econ Constraint

19. Comparison of Outcomes: The numbers

20. Comparison of Outcomes: The numbers 8 84 88 86 98 Model agrees with previous studies: recommends most effective control for whole population is children

21. Comparison of Outcomes: The numbers 95 99 89 98 99 Model demonstrates economics matter! Recommends most effective control for whole population is producers!

22. But what if we want to prevent most severe outcomes? Maybe we should still treat consumers first? 99 100 95 100 100 Nope! Still better to target producers for treatment – allowing them to continue supporting consumers helps consumers more!

23. But what if we want to prevent most severe outcomes? Maybe we should still treat consumers first? 9 90 95 93 100 That’s not true in the model without economic constraint.

24. Moral of the story: Economic constraints on families lead to different population-level optimal strategies for both limiting overall incidence AND limiting incidence in high-risk populations Model agrees that, without economic constraints, preventing disease in “reservoir” populations helps curtail risks to total population, but shifts recommendation once household production constraints are included Policy needs to be based on understanding productivity Optimal strategies in non-resource-limited areas may be wrong for resource-limited communities

25. Thanks to: Jacques Kibambe Ngoie (an economist who worked on this with me) DIMACS Also, Tami Carpenter and Immanuel Williams and I are working on extending these models to HIV/AIDS