What would happen if vaccine stocks disappeared overnight?

As a parent, I'd be terrified. As an expert, I'd be working overtime because the consequence would be millions of women, children and adults suffering needlessly from preventable diseases.

One of the things that vaccines make possible is the eradication of disease. So far, we've eradicated one human disease, smallpox, and we are really close with polio. Polio is on its last legs now that we've cornered it in just a couple of final populations in the world. That's only possible through the use of vaccines and requires everybody to use them for the whole world to benefit.

What diseases would resurge without vaccinations?

We're nearly to the point where there's not a single person paralyzed from the polio virus anywhere in the world. That would come back, and we would have needless, countless numbers of people paralyzed by a virus that we can prevent today. There would also be a resurgence of the epidemic diseases that not only kill or disable people, but strike fear in the hearts of people.

Imagine a world without the measles vaccine. That disease would spread quickly. If you dropped immunity to measles everywhere without a vaccination, you would rapidly get huge outbreaks in which 80% (or more) of people would become infected with measles. They would have severe fevers and rashes. Many of them would be hospitalized, some of them would die, and some of them would have life-long disabilities like blindness.

Imagine the social environment in which those kinds of diseases are running rampant, where people are afraid to be in contact with other people, where parents hold children back from playing with other children. You don't have to turn back the clock that long to actually find that period of time in the 1950s in the United States before we had polio vaccines. That's what happened. When there was a case of polio in the community, they shut down the community swimming pool. Kids stayed inside. The thing we take for granted is that the protection of vaccines allows that kind of freedom of interacting with people that the terror and living in fear of vaccine-preventable diseases would take away from them.

Babies and children are most vulnerable to infectious disease.
Image: Bill & Melinda Gates Foundation

Which populations are at highest risk without vaccines?

These diseases pick out vulnerable people first, so babies and young kids would be first. Other groups of people where their defences are weakened would be next, like those who are malnourished or people living with immuno-compromised conditions.

I think we should remember some of these diseases are lethal. Meningitis is the kind of disease that slays the teenage captain of the sports team or leads to an amputation, regardless of how energetic she was the day before. Cervical cancer and liver cancer are devastating illnesses that would come back, though more slowly because it takes a longer time to develop cancer. Now, those are two things that we're starting to control, because of vaccines, that would come back.

Why is World Immunization Week important?

Most people in rich countries have never seen the impact of infectious diseases like measles, diphtheria, meningitis, whooping cough. They don't fear them because they haven't seen them firsthand, because of vaccines. Diseases like epiglottitis, which is where your windpipe closes because of an infection. And if your two-year old child gets it, she can unexpectedly start gasping for breath. That kind of illness has disappeared from America and Europe because of one of our bacterial meningitis vaccines (the "Hib vaccine"). Paediatricians now don't ever see that disease. A lot of those “classic diseases” are gone now because we vaccinate people. So they're not afraid of it in places like the US, UK and Europe, and other well-to-do places.

You've noted that awareness of the danger of these diseases is important due to complacency in rich world countries. Why is vaccine awareness important in poorer regions?

Yes, so let me give you a great example of this. There's a part of Africa that is so impacted by epidemics of bacterial meningitis, its nickname is the "Meningitis Belt." It's a belt in the dry region of Africa that has been prone to huge epidemics of bacterial meningitis every three to five years. And now, as a result of the hard work of many people, an Indian vaccine manufacturer has created a vaccine specifically for the cause of that epidemic. It's widespread use is supported by Gavi funding so that now, we have virtually eliminated that cause of epidemic meningitis from Africa.

That was done by doing big campaigns in the affected countries. And what was amazing is when those campaigns were held, people would stand in line in temperatures over 40 degrees Celsius, or hotter, for hours, to be sure that they and their family members got vaccines against epidemic meningitis because every one of those communities had been affected by meningitis. Every one of those families, every one of those parents knew how important it was to get this protection.

Smallpox is the only human disease to have been totally eradicated by vaccines.
Image: Bill & Melinda Gates Foundation

How large an effort is needed to roll out vaccinations everywhere?

Global vaccinations work to protect women and children and communities every day from about 2.5 million preventable deaths a year right now. That success depends on a huge coordinated effort. We need manufacturers to make the vaccines. We need national government to buy the vaccines. We need donors to help subsidize that in some places. We need communities that demand the vaccines. And we need a huge health worker force to be able to deliver those vaccines at the right time in the right places.

It's mind blowing if you think about it, that the magic moment, that moment when a parent sits in a clinic with a health worker, that moment of vaccination, it typically takes about a minute. When you think about how much went into making that magic minute possible, it's mind blowing. And the fact that we do it tens of millions of times around the world every day is all the more incredible.

Interview by Poppie Mphuthing.

This Q&A has been edited for clarity.