The economics of vaccination

Rational social distancing policy during epidemics with limited healthcare capacity

Epidemics of infectious diseases posing a serious risk to human health have occurred throughout history. During recent epidemics there has been much debate about policy, including how and when to impose restrictions on behaviour. Policymakers must balance a complex spectrum of objectives, suggesting a need for quantitative tools. Whether health services might be 'overwhelmed' has emerged as a key consideration. Here we show how costly interventions, such as taxes or subsidies on behaviour, can be used to exactly align individuals' decision making with government preferences even when these are not aligned. In order to achieve this, we develop a nested optimisation algorithm of both the government intervention strategy and the resulting equilibrium behaviour of individuals. We focus on a situation in which the capacity of the healthcare system to treat patients is limited and identify conditions under which the disease dynamics respect the capacity limit. We find an extremely sharp drop in peak infections at a critical maximum infection cost in the government's objective function. This is in marked contrast to the gradual reduction of infections if individuals make decisions without government intervention. We find optimal interventions vary less strongly in time when interventions are costly to the government and that the critical cost of the policy switch depends on how costly interventions are.

Rational social distancing in epidemics with uncertain vaccination timing

During epidemics people may reduce their social and economic activity to lower their risk of infection. Such social distancing strategies will depend on information about the course of the epidemic but also on when they expect the epidemic to end, for instance due to vaccination. Typically it is difficult to make optimal decisions, because the available information is incomplete and uncertain. Here, we show how optimal decision-making depends on information about vaccination timing in a differential game in which individual decision-making gives rise to Nash equilibria, and the arrival of the vaccine is described by a probability distribution. We predict stronger social distancing the earlier the vaccination is expected and also the more sharply peaked its probability distribution. In particular, equilibrium social distancing only meaningfully deviates from the no-vaccination equilibrium course if the vaccine is expected to arrive before the epidemic would have run its course. We demonstrate how the probability distribution of the vaccination time acts as a generalised form of discounting, with the special case of an exponential vaccination time distribution directly corresponding to regular exponential discounting.

Supply chains create global benefits from improved vaccine accessibility

Ensuring a more equitable distribution of vaccines worldwide is an effective strategy to control global pandemics and support economic recovery. We analyze the socioeconomic effects - defined as health gains, lockdown-easing effect, and supply-chain rebuilding benefit - of a set of idealized COVID-19 vaccine distribution scenarios. We find that an equitable vaccine distribution across the world would increase global economic benefits by 11.7% ($950 billion per year), compared to a scenario focusing on vaccinating the entire population within vaccine-producing countries first and then distributing vaccines to non-vaccine-producing countries. With limited doses among low-income countries, prioritizing the elderly who are at high risk of dying, together with the key front-line workforce who are at high risk of exposure is projected to be economically beneficial (e.g., 0.9%~3.4% annual GDP in India). Our results reveal how equitable distributions would cascade more protection of vaccines to people and ways to improve vaccine equity and accessibility globally through international collaboration.

Convincing the "Herd" of immunity: Lessons from smallpox vaccination in 19th century Germany

Although vaccination is a cost-effective way to control infectious diseases, it is often met with popular resistance. Studying smallpox in 19th century Germany, this paper explores how economic incentives contribute to this phenomenon. The paper adds to the literature by combining mathematical epidemiology and unpublished archival evidence from two German states - Baden and Wurttemberg. The two states are an intriguing case because their initial conditions and vaccination laws were similar. Despite this, Baden experienced lower smallpox prevalence and higher vaccination uptake than Wurttemberg. The epidemiological model predicts that incentives to vaccinate decline rapidly when immunization reduces prevalence. The archival evidence reveals that Baden offset this decline by creating a public vaccination system which reduced costs for vaccinees and vaccinators alike. This suggests that the high fixed costs of centralized immunization policies can be compensated by economies of scale and popular acceptance.

VACCINE HESITANCY, PASSPORTS, AND THE DEMAND FOR VACCINATION

Vaccine hesitancy is modeled as an endogenous decision within a behavioral epidemiological model with endogenous agent activity. It is shown that policy interventions that directly target costs associated with vaccine adoption may counter vaccine hesitancy whereas those that manipulate the utility of unvaccinated agents will either lead to the same or lower rates of vaccine adoption. This latter effect arises with vaccine passports whose effects are mitigated in equilibrium by reductions in viral/disease prevalence that themselves reduce the demand for vaccination.

Optimal vaccine subsidies for endemic diseases

In Goodkin-Gold et al. (2021), we analyzed optimal subsidies for a vaccine against an epidemic outbreak like Covid-19. This companion paper alters the underlying epidemiological model to suit endemic diseases requiring continuous vaccination of new cohorts-also suiting an epidemic like Covid-19 if, following Gans (2020), one assumes peaks are leveled by social distancing. We obtain qualitatively similar results: across market structures ranging from perfect competition to monopoly, the subsidy needed to induce first-best vaccination coverage on the private market is highest for moderately infectious diseases, which invite the most free riding; extremely infectious diseases drive more consumers to become vaccinated, attenuating externalities. Stylized calibrations to HIV, among other diseases, suggest that first-best subsidies can be exorbitantly high when suppliers have market power, rationalizing alternative policies observed in practice such as bulk purchases negotiated by the government on behalf of the consumers.

On the management of population immunity

This paper considers a susceptible-infected-recovered type model of infectious diseases, such as COVID-19 or swine flu, in which costly treatment or vaccination confers immunity on recovered individuals. Once immune, individuals indirectly protect the remaining susceptibles, who benefit from a measure of herd immunity. Treatment and vaccination directly induce such herd immunity, which builds up over time. Optimal treatment is shown to involve intervention at early stages of the epidemic, while optimal vaccination may defer intervention to intermediate stages. Thus, while treatment and vaccination have superficial similarities, their effects and desirability at different stages of the epidemic are different. Equilibrium vaccination is qualitatively similar to socially optimal vaccination, while equilibrium treatment differs in nature from socially optimal treatment. The optimal policies are compared to traditional non-economic public health interventions which rely on herd immunity thresholds.

Integrated epi-econ assessment of vaccination

Using an integrated epi-econ model, we compute the value of vaccines for Covid-19, both under a planner's solution and in competitive equilibrium. The specific model, developed in Boppart, Harmenberg, Hassler, Krusell, and Olsson (2020), factors in not just value-of-life aspects along with standard economic variables but also the value of leisure activities that rely on a social component. We find that the societal value of vaccination is large; we estimate that, translated into monetary terms, the value of vaccinating one young individual in the competitive equilibrium is $17,800. Externalities are large: less than half the societal value is internalized by individuals (assuming that they act purely in their self-interest). Finally, behavioral responses are important, with a substantial share of the value of vaccines being attributed to people enjoying more socially-oriented leisure when more people are vaccinated.

COVID-19 vaccine hesitancy and vaccine passports: a cross-sectional conjoint experiment in Japan

OBJECTIVES

While the development of vaccines against the Novel Coronavirus (COVID-19) brought hope of establishing herd immunity and ending the global pandemic, vaccine hesitancy can hinder the progress towards herd immunity. In this study, by analysing the data collected when citizens undergo public health restrictions due to the pandemic, we assess the determinants of vaccine hesitancy, reasons for hesitation and potential effectiveness of vaccine passports used to relax public health restrictions on mitigating vaccine hesitancy.

DESIGN

Cross-sectional study, longitudinal study and conjoint experimental design.

SETTING

An online survey conducted in Japan in July 2021.

PARTICIPANTS

A demographically representative sample of 5000 Japanese adults aged 20-74.

PRIMARY OUTCOME MEASURES

COVID-19 vaccination intention RESULTS: We found that about 30% of respondents did not intend to get vaccinated or had not yet decided, with major reasons for vaccine hesitancy relating to concerns about the safety and side effects of the vaccine. In line with previous findings, younger age, lower socioeconomic status, and psychological and behavioural factors such as weaker COVID-19 fear were associated with vaccine hesitancy. Easing of public health restrictions such as travel, wearing face masks and dining out at night was associated with an increase in vaccine acceptance by 4%-10%. Moreover, we found that more than 90% of respondents who intended to get vaccinated actually received it while smaller proportions among those undecided and unwilling to get vaccinated did so.

CONCLUSION

With a major concern about vaccine safety and side effects, interventions to mitigate against these may help to reduce vaccine hesitancy. Moreover, when citizens are imposed with restrictions, vaccine passports that increase their freedom may be helpful to increase vaccination rates.

Challenges of integrating economics into epidemiological analysis of and policy responses to emerging infectious diseases

COVID-19 has shown that the consequences of a pandemic are wider-reaching than cases and deaths. Morbidity and mortality are important direct costs, but infectious diseases generate other direct and indirect benefits and costs as the economy responds to these shocks: some people lose, others gain and people modify their behaviours in ways that redistribute these benefits and costs. These additional effects feedback on health outcomes to create a complicated interdependent system of health and non-health outcomes. As a result, interventions primarily intended to reduce the burden of disease can have wider societal and economic effects and more complicated and unintended, but possibly not anticipable, system-level influences on the epidemiological dynamics themselves. Capturing these effects requires a systems approach that encompasses more direct health outcomes. Towards this end, in this article we discuss the importance of integrating epidemiology and economic models, setting out the key challenges which such a merging of epidemiology and economics presents. We conclude that understanding people's behaviour in the context of interventions is key to developing a more complete and integrated economic-epidemiological approach; and a wider perspective on the benefits and costs of interventions (and who these fall upon) will help society better understand how to respond to future pandemics.

Multi-generational SIR modeling: Determination of parameters, epidemiological forecasting and age-dependent vaccination policies

We use an age-dependent SIR system of equations to model the evolution of the COVID-19. Parameters that measure the amount of interaction in different locations (home, work, school, other) are approximated from in-sample data using a random optimization scheme, and indicate changes in social distancing along the course of the pandemic. That allows the estimation of the time evolution of classical and age-dependent reproduction numbers. With those parameters we predict the disease dynamics, and compare our results with out-of-sample data from the City of Rio de Janeiro. Finally, we provide a numerical investigation regarding age-based vaccination policies, shedding some light on whether is preferable to vaccinate those at most risk (the elderly) or those who spread the disease the most (the youngest). There is no clear upshot, as the results depend on the age of those immunized, contagious parameters, vaccination schedules and efficiency.

The Economic Burden of Influenza-Like Illness among Children, Chronic Disease Patients, and the Elderly in China: A National Cross-Sectional Survey

Background: The disease burden of seasonal influenza is substantial in China, while there is still a lack of nationwide economic burden estimates. This study aims to examine influenza-like illness (ILI) prevalence, healthcare-seeking behaviors, economic impact of ILI, and its influencing factors among three priority groups during the 2018–19 influenza season. Methods: From August to October 2019, 6668 children’s caregivers, 1735 chronic disease patients, and 3849 elderly people were recruited from 10 provinces in China to participate in an on-site survey. The economic burden of ILI consisted of direct (medical or non-medical) and indirect burdens, and a two-part model was adopted to predict the influencing factors of total economic burden. Results: There were 45.73% children, 16.77% chronic disease patients, and 12.70% elderly people reporting ILI, and most participants chose outpatient service or over-the-counter (OTC) medication after ILI. The average economic burden was CNY 1647 (USD 237.2) for children, CNY 951 (USD 136.9) for chronic disease patients, and CNY 1796 (USD 258.6) for the elderly. Two-part regression showed that age, gender, whether the only child in the family, region, and household income were important predictors of ILI economic burden among children, while age, region, place of residence, basic health insurance, and household income were significant predictors of ILI economic burden among chronic disease patients and the elderly. Conclusions: A large economic burden of ILI was highlighted, especially among the elderly with less income and larger medical burdens, as well as children, with higher prevalence and higher self-payment ratio. It is important to adopt targeted interventions for high-risk groups, and this study can help national-level decision-making on the introduction of influenza vaccination as a public health project.

[Is Mandatory Vaccination Against the Coronavirus Necessary?]

The end of the pandemic requires that SARS-CoV-2 vaccines be used. However, vaccination itself can lead to temporary adverse health effects and/or long-term damage. Vaccination initially represents a private good demanded by an individual cost-benefit calculus; however, it also creates positive externalities and thus too few individual incentives to vaccinate. Getting vaccinated is not a dominant rational strategy, neither in the overall population, nor among the old and the young, nor when the long-term costs of the pandemic are taken into account. It is all the more important to "price in" the long-term consequences of a lasting pandemic.

Willingness to Pay for Seasonal Influenza Vaccination among Children, Chronic Disease Patients, and the Elderly in China: A National Cross-Sectional Survey

Background: The disease burden of seasonal influenza is substantial in China, while the vaccination rate is extremely low, and most people have to pay 100% for vaccination. This study aims to examine willingness to pay (WTP) and recommended financing sources for influenza vaccination among children, chronic disease patients, and the elderly in China and determine feasible measures to expand vaccination coverage. Methods: From August to October 2019, 6668 children's caregivers, 1735 chronic disease patients, and 3849 elderly people were recruited from 10 provinces in China. An on-site survey was conducted via a especially designed PAD system. Tobit regression was adopted to predict the influencing factors of WTP. Results: The average WTP was 127.5 yuan (USD18.0) for children, 96.5 yuan (USD13.7) for chronic disease patients, and 88.1 yuan (USD12.5) for the elderly. Most participants in the three groups thought government subsidies (94.8%, 95.8%, and 95.5%) or health insurance (94.3%, 95.3%, and 94.5%) should cover part of the cost, and nearly four-fifths (80.1%, 79.5%, and 76.8%) believed that individuals should also pay for part. Tobit regression showed that a higher perceived importance of vaccination, knowing about priority groups, and considering that individuals should co-pay were promoters of WTP, while considering price as a hindrance lowered WTP. Conclusions: The WTP for influenza vaccination among children, chronic disease patients, and the elderly in China is fairly high, suggesting that price is not the primary hindrance and there is room to expand immunization. Most participants expected the government and/or health insurance to pay part of the cost, and such supportive funding could act as a promotive policy "signal" to improve vaccine uptake. Influenza-related health education is also needed to expand vaccine coverage.

Free and perfectly safe but only partially effective vaccines can harm everyone

Risk compensation can undermine the ability of partially-effective vaccines to curb epidemics: Vaccinated agents may optimally choose to engage in more risky interactions and, as a result, may increase everyone's infection probability. We show that-in contrast to the prediction of standard models-things can be worse than that: Free and perfectly safe but only partially effective vaccines can reduce everyone's welfare, and hence fail to satisfy-in a strong sense-the fundamental principle of "first, do no harm." Our main departure from standard economic epidemiological models is that we allow agents to strategically choose their partners, which we show creates strategic complementarities in risky interactions. As a result, the introduction of a partially-effective vaccine can lead to a much denser interaction structure-whose negative welfare effects overwhelm the beneficial direct welfare effects of this intervention.

Herd immunity and a vaccination game: An experimental study

Would the affected communities voluntarily obtain herd immunity if a cure for COVID-19 was available? This paper experimentally investigates people’s vaccination choices in the context of a nonlinear public good game. A “vaccination game” is defined in which costly commitments (vaccination) are required of a fraction of the population to reach the critical level needed for herd immunity, without which defectors are punished by the natural contagion of epidemics. Our experimental implementation of a vaccination game in a controlled laboratory setting reveals that endogenous epidemic punishment is a credible threat, resulting in voluntary vaccination to obtain herd immunity, for which the orthodox principle of positive externalities fails to account. The concave nature of the infection probability plays a key role in facilitating the elimination of an epidemic.

Strengthening vaccination programmes and health systems in the European Union: A framework for action

Vaccination is one of the most cost-effective public health interventions. However, the EU is facing increasing outbreaks of vaccine preventable diseases, with some fatal cases of measles. This paper reviews the main factors influencing vaccination uptake, and assesses measures expected to improve vaccination coverage. Obstacles to vaccination include concerns about vaccine safety and side effects, lack of trust, social norms, exposure to rumours and myths, and access barriers. Responses fall into three broad categories. Regulation, including the introduction of mandatory vaccination, can be justified but it is important to be sure that it is an appropriate solution to the existing problem and does not risk unintended consequences. Facilitation involves ensuring that there is an effective vaccination programme, comprehensive in nature, and reducing the many barriers, in terms of cost, distance, and time, to achieving high levels of uptake, especially for marginalised or vulnerable populations. Information is crucial, but whether in the form of public information campaigns or interactions between health workers and target populations, must be designed very carefully to avoid the risk of backfire. There is no universal solution to achieving high levels of vaccine uptake but rather a range or combinations of options. The choice of which to adopt in each country will depend on a detailed understanding of the problem, including which groups are most affected.

Identification of FimH derivatives as adjuvant vaccinated with PAc that enhance protection against Streptcoccus mutans colonization

FimH is the adhesin of type I fimbriae expressed on Escherichia coli that can mediate specific adherence to host cells. High binding mutations in FimH are related to the adaptive evolution of bacteria. However, additional roles that these allelic variations may play remain elusive. To investigate novel biological functions of the mutations in FimH, we introduced four different variants of FimH by incorporating single amino acid substitutions at specific sites, namely A25P, G73R, A106, and T158P, respectively. In this study, adjuvant potential of FimH variants was evaluated by investigating their ability to trigger innate immune response to DC2.4 and adaptive immunity to improve immunological characteristics. The data revealed that purified A106 and T158P up-regulated the expression of co-stimulatory molecules critically involved in DC2.4 activation by interaction with TLR4, whereas A25P and G73R did not induce the phenotypic maturation of DC2.4. Besides, the culture of DC2.4 with A106 and T158P enhanced the release of cytokines and protein phagocytosis. When formulated with PAc, T158P elicited more robust PAc-specific IgG and IgA antibody responses compared to PBS, PAc and PAc+K12 groups and inhibited bacteria colonization. Collectively, the results confirmed that the T158P mutation located around the inter-domain interface of the protein induced a specific enhancement effect on adjuvant characteristics.

The optimal treatment of an infectious disease with two strains

This paper explores the optimal treatment of an infectious disease in a Susceptible-Infected-Susceptible model, where there are two strains of the disease and one strain is more infectious than the other. The strains are perfectly distinguishable, instantly diagnosed and equally costly in terms of social welfare. Treatment is equally costly and effective for both strains. Eradication is not possible, and there is no superinfection. In this model, we characterise two types of fixed points: coexistence equilibria, where both strains prevail, and boundary equilibria, where one strain is asymptotically eradicated and the other prevails at a positive level. We derive regimes of feasibility that determine which equilibria are feasible for which parameter combinations. Numerically, we show that optimal policy exhibits switch points over time, and that the paths to coexistence equilibria exhibit spirals, suggesting that coexistence equilibria are never the end points of optimal paths.