In Steven Pinker’s most recent book, Enlightenment Now, the psycholinguist makes an interesting observation about the first line in a Wikipedia entry: “Smallpox was an infectious disease.”

The key word here: “was.”

Though the viral disease killed more than 300 million people in the 20th century, it’s now a thing of the past — the only scourge spread in humans to have been eradicated. (The other disease that’s been eradicated, rinderpest, was spread mainly in cattle.)

May 8, 2018 is the 38th anniversary of this achievement. On this day, the World Health Assembly declared the world officially smallpox-free, three years after the last case popped up in Somalia. And William H. Foege, a former director of the Centers for Disease Control and Prevention, is the man who came up with the global strategy that helped turn a gruesome and painful illness into something we now refer to in the past tense.

In his excellent 2011 book House on Fire, the 82-year-old physician and epidemiologist describes how he and other health workers got to smallpox eradication — by dreaming, being savvy in politics and unafraid to break the rules, and devising the brilliant ring vaccination strategy. The unique approach to immunization meant that instead of vaccinating entire populations to prevent illness, the limited supply of shots could be distributed among the people most at risk: the contacts of the infected.

Building on that success, humans have nearly eliminated measles and polio, vastly decreased the incidence of malaria and HIV/AIDS, and invented a successful Ebola and HPV vaccine, among many other public health milestones.

Lately, though, we’ve forgotten these achievements — especially because many people no longer see the diseases science helped stamp out. This year was also the 20th anniversary of the research paper by Andrew Wakefield that helped catalyze the modern anti-vaccine movement by suggesting vaccines cause autism. (That same movement has been linked to recent measles and whooping cough outbreaks.) So the anniversary of smallpox eradication felt like a good time to take stock.

I called Foege to discuss his life’s work, how he feels about the anti-vaccine movement, and which diseases he thinks humans will conquer next. Our conversation has been edited for length and clarity.

Julia Belluz

In your book, you begin by discussing an odor — the smell of decaying flesh from smallpox pustules that hit you before you even entered the room with the infected patient. And you go on to say that hundreds of years before you began working on smallpox, the origin of the dream to eradicate it started with Edward Jenner, who invented the smallpox vaccine. Today we’re living in this moment where a lot of the discussion around vaccines is framed negatively — many people have forgotten how terrible diseases like smallpox were, and what an achievement vaccines are.

William Foege

I think vaccines are really the foundation of public health. I often say that modern public health started in the spring of 1796, when Jenner did the first smallpox vaccination. He took material from the cowpox lesion and inserted this into the arm of a boy named James Phipps. Weeks later, he tried to give [Phipps] smallpox and was not successful.

That was the beginning of modern public health — the first time we had a tool. The vaccine era took some time to get going.

By the early 1980s, [many of] our vaccine diseases had gone down to close to zero. We’ve really done an incredible job in this country. And by 2000, we had even interrupted measles transmission. Measles is so infectious, everybody thought that would be an impossible goal. So things were going quite well until Andrew Wakefield did his Lancet article [suggesting there’s a link between the measles-mumps-rubella vaccine and autism].

He specifically said the MMR vaccine was the problem. He was disbarred in England because of the falsifications of his [data]. He continues to have lots of people who believe this relationship is the reason for autism in their children. These parents are trying to do the best things they can for their children. I always start from that premise. He has really spoiled the situation.

Julia Belluz

Sometimes, when I read about the anti-vaccine movement, I wonder how you must feel knowing what a nasty and painful disease smallpox was, and knowing vaccines helped eliminate it, and that there are people who now reject vaccines.

William Foege

We get very frustrated if we know the truth is not being understood.

But the anti-vaccination movement started right after Jenner. You saw cartoons of the head of a cow coming out of the arm of a child who was vaccinated, that sort of thing.

The second thing is parents are trying to do the right thing, but nowadays [some] only can see the risk of vaccine. They no longer can see the risk of disease.

You combine that with reluctance many people have to believe the government. This really is a problem. So I see the problem as being even bigger in future.

The thing that impressed me, though, in India, even though they had a smallpox goddess — which they saw as a positive thing — they changed their mind when they could see that vaccination protected against smallpox. They didn’t want their children to have smallpox. So that belief was quickly overcome by just the facts. And you would hope the same thing could happen with education, that parents would understand what the risk is of the disease coming back and could actually picture that versus the risk of vaccines.

Julia Belluz

Which current efforts to eliminate diseases make you most hopeful? Polio? Guinea worm?

William Foege

I think there are a couple of bright spots on the horizon. I have advocated that all obstetricians should tell their pregnancy patient you never have to worry about the rubella syndrome in their child. The reason is rubella no longer circulates in this country. So many children receive the vaccine, they have protected your child. This is part of the social contract that protects your child — and you have an obligation to continue to the social contract in your future.

Polio has turned out to be much more of a social problem than a scientific problem. That is, in Pakistan and Afghanistan, we are dealing with the difficulties of politics. And much of this, of course in Pakistan, is due to the US trying to use [a hepatitis B vaccine] program to get DNA to figure out which house Osama bin Laden was in. That angered people in Pakistan to the point they’ve actually killed polio vaccinators. Who could have imagined that a dozen years ago? So the fact that we didn’t get this over with as fast as we should have has led to one complication after another. We’ll still get rid of it; it’s just taking longer.

With guinea worm, there’s no vaccine involved. [Eradication involves community-based interventions to reduce transmission.] That should give us courage to look beyond vaccine-preventable diseases.

There’s been, at the Carter Center, a task force for disease eradication that’s looked at dozens and dozens of diseases asking what more information we’d need in order to eradicate the disease. That’s a different question from saying can we eradicate this disease? By going through that process, we develop the research agenda.

I think after polio and guinea worm, we could well be looking at river blindness, lymphatic filariasis — and I think measles should be on the list because, again, we have a good vaccine and the number of measles deaths has gone from 3 million per year to about 100,000 this last year. That’s a very significant reduction, and it shows we know a lot about how to stop that disease.

Julia Belluz

In your book, you talk a lot about the importance of optimism — and it seems you are holding on to that optimism, even with all the setbacks you’ve described.

William Foege

I think we’re at the beginning of an eradication era — because of vaccines — and as we learn more and more about logistics, cold chains, how to develop vaccines that don’t require refrigeration, don’t require using needles and syringes, I think the future is very bright for disease eradication.

I say in the book some things have to be believed to be seen. I think that’s very true with eradication of disease. You have to believe a disease can be eradicated; then you have to put up with all the frustrations about things that don’t work quite right. … Then you stick with your vision of what the last mile is.

Clarification: While polio vaccinators had accessed the Bin Landen compound to administer the vaccine in the past, the CIA Bin Laden operation involved a hepatitis B vaccine campaign. We’ve clarified that in Dr. Foege’s transcript.