The world spent about $97.9 billion in the years since 1994 trying to develop new tools to fight infectious diseases in poor countries. That includes things like vaccines, treatments, diagnosis tools, and preventative tools like bed nets for diseases like malaria. 

That sounds like a lot of money, and it is. But Policy Cures Research, the organization that came up with that number, also tried to estimate the benefit that this research generated. They got a dollar figure there, too: $49.7 trillion. The full investment will avert, the report finds, about 40.7 million total deaths between the years 2000 and 2040.

These are big claims that deserve scrutiny. But they hold up. 

The finding is particularly important at a moment when key institutions like the World Health Organization, the vaccine fund Gavi, and the Global Fund to Fight AIDS, Tuberculosis, and Malaria are all conducting fundraising drives, ones that world leaders have yet to respond to with adequate investment. The resistance is understandable (these are big sums) but short-sighted.

There are massive gains to be won by investing more to develop cures, treatments, and vaccines for the world’s deadliest infectious diseases. We just have to do it.

The study focused on what Policy Cures calls “neglected diseases.” That means infectious diseases that primarily affect the developing world. Their burden is enormous. Respiratory infections and tuberculosis were responsible for 153 million years of healthy life lost in the year 2019. That’s about double the injury toll of car accidents worldwide.

The report found 183 new technologies targeting these diseases approved between 1999 and 2023. It hired an outside firm, Avenir Health, which used data from the Global Burden of Disease study to model how much they have cut death and disease to date. In some cases, the authors also had to extrapolate. Some technologies, like the RTS,S and R21 malaria vaccines, only won backing from the World Health Organization in the past couple years, so the authors estimated the benefit these will have if/when they’re rolled out.

In total, they estimate that these technologies will wind up saving 2.47 billion years of life (after adjusting for lives saved in the future). That’s about 40.7 million total lives saved. It’s a gargantuan, gargantuan total.

Calculating ROI for global health investments is tricky. First you need to know what the investments cost. The total cost spent on these technologies to date is $97.9 billion. Pushing through promising tools currently “in the pipeline” that could be rolled out before 2040 will cost another $24.8 billion, for a total cost of $122.7 billion.

Then, putting a dollar value on the benefits accrued requires making some judgment calls. 

The bulk of the benefits come from saving lives and preventing illness. To calculate an ROI number, you have to put a monetary value on those saved lives and prevented illnesses, a value you can then compare to the upfront investment cost. The report values each year of healthy life saved at $19,985. Multiply that by 2.47 billion life years saved by these technologies, and you get about $49.4 trillion. 

Add in their estimates of the general economic benefits communities accrue because workers and dependents are less burdened by disease ($269.8 billion), and you get the $49.7 trillion in total benefits the report finds, or $405 for every dollar invested.

Even that ROI is arguably an undercount.

The $19,985 per life year figure that drives 99 percent of these benefits is a variant on what’s known as the “value of a statistical life,” and calculating it is among the most complex and controversial tasks in economics.

Typically, the value is estimated by measuring what individuals are willing to pay to reduce their risk of dying. The idea is that people’s actual spending gives a truer sense of their feelings than, say, polling them would. But people in poor countries are willing to pay less than people in rich countries, for the obvious reason that they have less money. This approach tends to conclude that lives in poor countries are literally worth less. Indeed, the Policy Cures report uses smaller values of a statistical life for poor countries.

In a subsection, they generate estimates where every life counts equally. Using a value for the US ($12.3 million) and applying it to every human being equally, they get an ROI of over $9,000 per dollar invested — which the report rejects as “potentially unrealistic and harmful to the project’s credibility.”

I think that $9,000 figure is more realistic. Setting a lower value makes some sense for, say, the government of Nigeria; the statistic gives policymakers a sense of how much their citizens are willing to pay to save their lives, in situations where they will be the ones paying.

But poor country governments are not the main funders of malaria vaccine research. The funders are governments and foundations in rich countries — groups in the global north, in other words. Those groups should be valuing every life equally, and highly.

The bulk of these billions of life years have already been saved, but some are yet to come. The report estimates malaria vaccines will save about 370 million life years from now until 2040. But malaria vaccines have only barely begun rolling out. The first vaccine, RTS,S, took decades to be released, and even now advocates are raising the alarm that we don’t have enough money to fund a full rollout to every child who needs a vaccine.

These vaccines might save 370 million life years, but they might not. We need to invest in getting them to people who need them.

This is an immensely hopeful report. But it’s a report that also serves as a call to arms. Rich countries need to get their act together, fast, or this opportunity will slip through our fingers, with poor children in Africa and South Asia paying the price.

This story originally appeared in Today, Explained, Vox’s flagship daily newsletter. Sign up here for future editions.