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World leaders, beckoned by President Biden, are assembling on Earth Day, April 22, to create greater urgency to fight climate change. The summit is taking place during the worst infectious disease pandemic in a century.

World leaders need to pay heed to the climate change warning signs that have been flashing for decades. Scientists and policymakers have long predicted that as human migration due to weather extremes brings people into closer contact with animals harboring novel pathogens, humanity will face increasingly grave health risks, including future epidemics and pandemics.

There has never been a question of if this will happen, but rather a question of when. Had governments heeded the warnings provided by the spread of emerging diseases like HIV, Ebola, SARS, and MERS, the world might have avoided some of the catastrophic social, economic, and global health consequences caused by SARS-CoV-2. Yet when given the option for investing sooner in pandemic preparedness or paying substantially more later, society chose the latter.


Covid-19, which has already caused more than 140 million cases, 3 million deaths, and trillions of dollars in economic losses, has laid bare the enormous costs of failing to prepare. It’s time to heed the warning signs and make the necessary investments to fight climate change and mitigate its impact on global health.

Across the spectrum of diseases, humans already face large health-related risks from climate change. Global warming has placed 1 billion more people at risk of mosquito-borne diseases, including dengue, Zika, and malaria. Greater frequency and intensity of hurricanes has accelerated outbreaks of life-threatening gastrointestinal diseases like cholera and typhoid. Extreme heat is the leading weather-related killer in the United States, with longer droughts causing malnutrition and stunting the growth of children. Wildfire smoke degrades air quality, increasing the rates of lung cancer, asthma, and other respiratory diseases, and can also trigger chronic inflammation and autoimmunity.


Despite clear warning signs, governments have yet to adequately fund efforts to mitigate the ever-increasing health threats due to climate change.

Vaccines are among the greatest public health interventions in human history, having brought many infectious diseases under control. Unfortunately, vaccines are usually less effective among the most vulnerable populations, including older adults and newborns. And so far, no vaccines exist for the major global diseases exacerbated by climate change, which include AIDS, tuberculosis, malaria, and cancers.

What’s the biggest obstacle impeding progress against these diseases? Our limited understanding of the human immune system.

The human immune system, or immunome, holds the keys to prevention and control of infectious and noncommunicable diseases. Twenty years ago, the human genome was sequenced in a global effort that took more than a decade and cost nearly $3 billion. It helped propel a revolution in biomedical research.

Until now, decoding the immunome has remained beyond reach due to its scale, its complexity, and limitations in technology. Today it is possible to sequence a genome in one day for less than $1,000, and undertake systems biological assessments ranging from the microbiome to the exposome. For the first time, researchers can analyze volumes of data using supercomputers and artificial intelligence to provide new insights on human immunity and novel approaches for vaccine development.

Worldwide trends point toward a future in which devastating diseases will become even more widespread due to climate change, human migration, and the growth and aging of populations. As Covid-19 has demonstrated, disease knows no borders in an interconnected world.

To reduce these threats, governments must make greater investments in climate-change solutions. The world needs both a reduction in global greenhouse gas emissions and increased preparedness for negative climate impacts, which would include the development of novel approaches for the prevention and control of major global diseases.

With the lessons of the pandemic still being learned and the necessary tools for decoding the human immune system at the ready, now is the time for world leaders to focus on reimagining and reshaping the future of human health. Increasing investments in understanding the principles of creating effective immunity for vulnerable populations is a promising place to start.

Alice Hill is a senior fellow for energy and the environment at the Council on Foreign Relations and former special assistant to the president and senior director for resilience policy on the National Security Council. Wayne C. Koff is the president and CEO of the Human Vaccines Project and adjunct professor in the Department of Epidemiology at the Harvard T.H. Chan School of Public Health.