3.6 Equitable distribution of vaccines – allocation rules

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effective in increasing full immunization rates among young children in India (Banerjee, Duflo, Glennerster, and Druva, 2010).

Nonetheless, cash or in-kind incentives might be unaffordable as a strategy for many countries in South Asia that already struggle to cover the cost of procuring COVID-19 vaccines. In these contexts,other optionshave been shown to achieve high coverage for childhood immunizations and may apply in this case, including ensuring vaccines are free of charge, home visits, reminders, and well-designed information campaigns. Regardless of the mix of interventions, a decline in trust in health workers and the government will stall COVID19 vaccines’ uptake. Countries canbuild trustthrough clear and understandable communication, informing campaigns with feedback from communities, and mobilizing trusted advocates to lead stakeholder engagement.

As countries work to strengthen the supply-side challenges to procuring and deploying vaccines, they would do well not to ignore the demand-side. National programs can draw on behavioral insights that address the drivers of hesitancy and ensure as many people as possible receive a safe and effective COVID-19 vaccine.

Note: this box was written by Damien de Walque and Nayantara Sarma.

3.6 Equitable distribution of vaccines – allocation rules

The limited supply of vaccines over the next year or so and constraints affecting the distribution of vaccines confront governments with the challenge of choosing the most equitable and efficient rules for distributing vaccines. However, the principles involved in determining what is equitable or efficient are unclear, and at times the two goals may conflict. For example, it may be viewed as equitable to distribute the vaccines across regions in relation to the population size. However, this approach may not allow any region to ease restrictions on trade and movement, so distributing the same amount of vaccine across all regions (a form of equitable distribution) may mean sacrificing income. Since poor areas tend to have higher incidences of infection, it could be viewed as equitable to distribute more vaccines to the poor. But higher immunity levels in these areas may imply that the benefits of vaccination are smaller than in areas with few infections so far. And it would likely be viewed as inequitable to provide more vaccines to men than to women, but men have a higher risk of dying, so vaccinating men may be more effective in saving lives.

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The rules governing distribution need to be simple so that eligibility is easily determined by individuals and easily verified by those distributing the vaccine. The rules should also conform to widely accepted ethical precepts to avoid implementation obstacles and encourage take-up. Decisions about tradeoffs between equity and efficiency when formulating vaccination plans must be aware of ethical, political, and social concerns.

Given the context-dependent impact of different rules for vaccine distribution and the different ethical perspectives that policy makers may bring to this decision, it is difficult for economists to recommend how to set priorities. Instead, our goal here is to show that the size of the economic benefits (to society and individuals) varies, depending on which subgroups of the population are targeted.

We illustrate some of the issues involved in using data from Tamil Nadu and the methodological framework explained in Box 2. That is, we analyze the impact of targeting different population groups in Tamil Nadu for vaccine distribution to provide some insight into what policy makers should take into account in exploring this problem. There are many possible ways of targeting vaccines that could improve social welfare compared to a random distribution or a first-come, firstserve approach. However, there is a premium on simple rules that can be easily verified in poor countries with limited administrative capacity and data availability. We will look at the impact of vaccine distributions based on age.

Targeting the elderly, as is done by most countries that are distributing vaccines against COVID-19, saves lives. Figure 10 compares forecasts of the number of deaths from COVID-19 in Tamil Nadu under various distribution rules. With 50 percent of the population vaccinated, the number of COVID-19 deaths falls by 14 percent more if the elderly are targeted than if vaccines were allocated randomly. As mentioned above, a decline in life years lost is also achieved by targeting the old. Risk factors, such as obesity, diabetes, cardiovascular disease, and chronic respiratory disease, are correlated with age, so prioritizing vaccine access by age will largely mirror prioritization by health risk factors. Figure 10 also shows that a “mortality prioritized” allocation, i.e., an allocation that considers the higher infection fatality rates (which is equivalent to targeting older groups), achieves better results than random or contact rate-based allocations. The latter considers the mixing of individuals and is based on contact tracing studies, such as Laxminarayan et al. (2020). The fact that random assignment and contact rate priority assignment do not differ much from the no vaccine scenario is because the probability of contracting the virus in Tamil Nadu has waned due to the already quite high level of seroprevalence. This underlines the importance of speed and adopting sensible rules for the allocation of vaccines.

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Figure 3.10. Impact on number of deaths of alternative vaccine allocation rules, Tamil Nadu

390

370

Deaths 350

330

310

290

270

250 no_vax contact random mortality contact random mortality 25 50 median percentile05 percentile95

Source: Malani et al. (2021).

Box 2: Methodology for modeling impact of COVID-19 by population groups

On the epidemiological side, we use a compartmental model to simulate the pandemic’s progression. In such compartmental models, each member of the population is assigned to a compartment reflecting their infection status: susceptible, infectious, recovered, or deceased. This set of compartments, known as a SIRD model, is the most parsimonious, given available data. The class of compartment models is also described by a parameter known as the reproductive rate, or the number of secondary infections induced by a current infection. With the estimated reproductive rate, the compartmental model can be run forward to estimate the population’s future infection risk. Reproductive rates and mortality are estimated by applying a Bayesian learning procedure to recent data on reported case prevalence and seroprevalence.

On the economic side, we employ an economic model of lifetime utility. We calculate the social value of vaccination as equal to the private willingness to pay for the equivalent of the expected consumption from vaccination, where expectations reflect survival probabilities obtained from our epidemic forecasting, given a vaccination policy. The incremental social value is the difference between the social value under a vaccination or a no vaccination policy We specifically choose to use consumption rather than income to measure economic benefits to capture the benefits of vaccination to household members who are not in the workforce.

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The link between these two models occurs by mapping infection levels to economic consumption levels. To do so, we obtain household-level monthly consumption from January 2018 to October 2020. We regress the percentage decline in consumption relative to average 2019 consumption for the household against an array of fixed effects and indicators for different levels of local infection rates and deaths from official reports. Under the regression’s structure, when COVID-19 cases vanish, average monthly consumption will return to average 2019 levels before growing again. We project household consumption using this regression and forecasts of local infection and death rates from our epidemiological simulations.

The aggregate private benefit for each vaccination policy is calculated in two steps. First, for an individual in a given age category and district, we estimate the benefit from (a) getting a vaccine that is 70 percent effective (similar to the Asta Zeneca vaccine approved in India) and (b) living under the vaccination policy even though one is not personally vaccinated. In each scenario, daily age- and location-specific survival probabilities are obtained from epidemic simulations. Analog daily consumption is obtained from the consumption forecast with the additional assumption that, if one is personally vaccinated, per capita consumption returns to 2019 levels. Second, the average per capita private benefit is a weighted average of age-specific benefits, where the weights are the share of the local population in each age category.

When employing the economic model for valuation, we separate value into age-specific direct benefits to the target person being vaccinated (based on the probability of dying if infected and life years lost as a result) and age-specific indirect benefits or externalities to persons who avoided infection from the target person (based on economic recovery). To estimate the indirect benefits of vaccinating a person in a given age category, we take two steps. First, we project the daily reproductive rate of the epidemic in each age group. Second, we determine the share of each age group’s projected infections that are due to every other age group using the India and COVID-specific contact matrix from a contact-tracing study of two Indian states. Third, we allocate the aggregate private benefit of avoiding each day’s infections to each age group based on the last step.

Note: this box is based on Malani et al (2021).