Every summer for most of human history, parents watched their children with dread. Not because summer was dangerous in the way we mean today — it was something more specific and more terrible. Pools were closed. Crowded places were avoided. A child who woke up with a fever and leg pain was a child who might never walk again. Polio was seasonal. Parents knew this. They planned around it. They feared it the way you fear something that doesn't announce itself before it takes.
That was the normal condition of human life before vaccines. Not the exception. The norm.
In the 20th century alone, smallpox killed an estimated 300 million people — more than all the wars of that century combined. Before Edward Jenner developed the smallpox vaccine in 1796, the disease killed roughly one in three of those it infected and blinded many of those it didn't. In 18th century Russia, every seventh child born died from smallpox. It was not an anomaly to dread. It was a tax that nature collected on the act of being born.
We ended it. With a vaccine. In 1980, the WHO certified smallpox eradicated — the only human disease ever fully extinguished. That is one of the most extraordinary achievements in the history of our species and was led by DA Henderson, a mentor to me and larger than life Homeric hero.
What vaccines actually are
We haven't properly understood what vaccines are. They are liberation technology. They are what happens when human beings refuse to accept nature's terms.
Energy expert Alex Epstein has a concept he calls "climate mastery." His core argument is that the right question about climate isn't how to minimize our footprint — it's how to build the technological capacity to master climate dangers. Humans don't just "adapt" to storms, drought, and extreme temperatures; we build levees, irrigation systems, and weather-forecasting networks. The result: climate-related deaths have fallen roughly 98% over the last century, even as the human population more than tripled.
The same principle, applied to the microbial world, is what I'd call infection mastery. Nature has never been on our side. Viruses and bacteria do not intend harm — they have no intentions at all. They replicate, mutate, and spread because that is what selection pressure optimized them to do. Infectious disease has always been the price of living on a planet that was microbial long before it was human. For most of history, that price was paid in full — with paralyzed limbs, blind eyes, dead children, and shortened lives. There have been 10,000 generations of humans and it’s only the last 4 that humans have been able to master some infectious diseases.
Vaccines are infection mastery in concentrated form. They don't ask us to accept the disease burden nature imposes. They allow us to build immunity without paying the cost of the disease itself — to take the lesson without the punishment. The result: polio, which paralyzed tens of thousands of American children per year in the 1950s, has been eliminated from the Western hemisphere. Measles, which killed 2.6 million people per year before the vaccine, is now eminently preventable — when we bother to use it. The HPV vaccine prevents cervical cancer. The flu vaccine reduces heart attacks. The shingles vaccine cuts stroke risk. These tools don't just stop infections; they reshape the entire downstream arc of a life.
The misunderstanding that keeps getting people killed
Some people frame vaccination as humans "interfering" with nature, as if nature had a preference worth respecting. But this gets the relationship exactly backward. The human immune system, the human brain, the capacity for abstract reasoning that lets a scientist synthesize an mRNA vaccine in a year — all of that is nature. It evolved. When we make a vaccine, we aren't defying natural selection. We are what natural selection produced: a species capable of turning reason outward onto a hostile world and making it less lethal. On my first trip to the Galápagos, where Darwin amassed the observational data needed to formulate the theory of evolution via natural selection, a naturalist guide told me humans shouldn't interfere with how infectious disease shapes our species. My answer then is what it is now: building tools to master infection is the most natural thing we do. It is natural selection completing itself through us.
This is why the current erosion of vaccine confidence isn't just a public health problem. It is a civilizational one. Measles is spreading across American states not because we lack the tools to stop it, but because we have chosen to walk away from them — to voluntarily return to a world our grandparents spent their lives escaping. The West Texas outbreak, the Florida cases, exposures at Lincoln Center, and South Carolina— these aren't bad luck. They are the predictable result of surrendering infection mastery to ideology.
If a 98% reduction in climate deaths counts as mastery, what do we call the eradication of smallpox? What do we call a world where your child doesn't spend August in fear of a limp? We call it what it is: a triumph of human reason over nature's indifference. And it is ours to lose.