Q&A: Peter Salk on the Lessons Learned from Vaccine Development History

Peter Salk was 11 years old when a University of Pittsburgh team led by his father, the late Jonas Salk, created the inactivated poliovirus vaccine. The day of the 1955 announcement that the vaccine was safe, effective and potent, “everything just went crazy,” he recalls. “There were so many calls from reporters that we ended up having to get an answering service. Imagine how embarrassing that would be for a sixth grader.”

Today, at 76, he’s back in the spotlight, fielding calls from the media as researchers around the world race to develop new vaccines to stem the COVID-19 pandemic.

As a physician, a professor of infectious diseases and microbiology at Pitt and a researcher who has studied treatment and prevention strategies for a number of diseases, Salk embraces these opportunities to help put the challenges of the current crisis in their broader historical context. Recently, Pitt Med magazine senior editor Elaine Vitone caught up with him via Zoom from his home in La Jolla, California, where he heads the Jonas Salk Legacy Foundation. See the video.

On Oct. 15 from 10 to 11:30 a.m. ET, Salk will team up with experts from Pitt, the March of Dimes, the Wilson Center and more for a discussion of the new pandemic in light of the old. The event is free and open to the public. Attendees must register at the Wilson Center website. 

What was life like before the inactivated poliovirus vaccine, and how did it change after?

The worst year in this country was 1952, when nearly 58,000 people contracted polio. More than 21,000 were left with permanent paralysis and about 3,000 died. If an epidemic came, there was no way parents were able to protect their children. People were just terrified.

Then, overnight, the fear was lifted.

My father's name is the one that is most often associated with this, but he wanted it to be called the Pitt vaccine. All of the members of the team deserve credit for the success of that effort. The people of Pittsburgh stepped up to the plate and allowed their children to take part in the early trials. And this was not a government funded program. It was funded by the people themselves, through the efforts of the March of Dimes (the fundraising arm of the National Foundation for Infantile Paralysis), collecting dimes in movie theaters, going door to door. This was the people’s victory against this illness.

What can we learn from history as we look to the future of vaccine development?

One of the concerns that I have is that when you're trying to move quickly with a vaccine, you need to be sure that you've done the appropriate preclinical work in animals and look carefully at what the effects of the different types of vaccines are on the immune system. Because vaccines can have effects that might not have been predicted. A few vaccines have actually made disease severity worse if you got the illness.

The second poliovirus vaccine, which used a live virus and was produced by Albert Sabin, has a significant side effect. Genetic changes can cause the vaccine virus to revert to virulence and be able to cause paralysis. In part because this vaccine is administered orally, which is more convenient and less expensive, it ended up becoming the vaccine of choice in this country from 1963 to 2000. And year after year during that time, something on the order of eight to 12 cases of polio each year in this country were caused by the oral vaccine itself. So the decision was eventually made to go back to the inactivated poliovirus vaccine in the United States.

So one has to be careful. But I think that as long as a completely scientific procedure is followed, starting with all of the right experiments, and then moving into human trials with careful monitoring along the way, we ought to be able to get to a point where we have not just one, but multiple vaccines that will end up being useful.

What was the Cutter incident?

When working on the development of the inactivated poliovirus vaccine, my father and his research team used exquisite care to determine how to go about it in a way that one could be completely sure there would be no live poliovirus left in the vaccine. There was precise definition of how long you needed to expose the virus to the inactivating chemical, measuring virus survival at each point along the way, so the virus would be killed in a predictable fashion. In addition, great care was taken by the National Foundation for Infantile Paralysis to be sure that the two manufacturers of vaccine used in its large-scale nationwide field trial were consistently able to produce safe batches of vaccine.

Once the field trial was over, though, neither the foundation nor my father had control over the production and monitoring of commercial batches of vaccine. One of the new manufacturers, Cutter Laboratories, did not pay full attention to instructions and turned out lots of vaccine that contained residual live poliovirus. All told about 120,000 children were injected with improperly made vaccine, and another hundred thousand people were infected as a result of contact with those kids. 159 people ended up paralyzed and 10 people died. It was absolutely devastating.

Following that tragedy, measures were put in place by the government to ensure that the manufacturing of the vaccine would be done correctly, and there have not been any further errors of that type. There has been an enormous strengthening of the whole regulatory oversight system with respect to approval and monitoring of vaccines. The 2005 book by Paul Offit (MED ’80), “The Cutter Incident,” details the far-reaching consequences of this event.

What are your thoughts on the anti-vaccine movement?

While one should have an awareness that vaccines in some circumstances can have side effects, it's really important to differentiate between what's real in terms of problems and what's not real. Things have gotten out of balance. The fear that's been caused by concerns that haven’t ended up holding water (such as the idea that vaccines cause autism) has created a lot of difficulty.

As a result of vaccines that have been introduced over the decades, many diseases that once plagued children, such as polio, whooping cough and measles, have been brought under control. Some parents are now letting their guards down because they just aren't aware of what it was like before these vaccines came on the scene.

A recent article describes how in 1954, the year before the polio vaccine came out, 31% of people said that they would not be willing to take the new vaccine themselves. But that changed after the success of the field trial and after the rates of polio began to go down following the introduction of the vaccine. I think that's probably the way things will go today with COVID-19.

In addition to overcoming scientific and logistical challenges, what else do you believe it will take to end the COVID-19 pandemic?

When this epidemic first started, I was struck by how well people cooperated with the need to change behaviors, stay home and avoid interactions that might facilitate spread of the virus. But then something began to change, with the emergence, for example, of resistance to wearing a mask because it is “infringing on my civil liberties.” We've ended up with divisiveness, which I think has been harmful.

I think that one of the things that would contribute to ending this epidemic would be turning down the heat that is helping to fuel dissension and instead following well-motivated and scientifically supported recommendations about how one might protect oneself and protect others. I think that we need to have a greater emphasis on harmony, on appreciating one another and appreciating that we are in fact all in this together. How I behave affects you, how you behave affects me, how we collectively behave affects everyone in this country. And it would be good if each of us could extend this same degree of caring and concern to the rest of the world.

The epidemic in a way is presenting an opportunity for us to take some constructive steps into the future. There's been a heightened sensitivity about differences within subsets of our population. The epidemic has been affecting to a greater degree Black, Hispanic and Native American communities, probably not as a result of genetic factors, but rather because of socioeconomic factors that promote susceptibility. There's been a growing awareness about some of these deeply ingrained inequalities within our country.

I think that as devastating as this epidemic has been, there are ways in which we may experience some improvement in the quality of life in society as we come out the other side.

This interview has been edited for length and clarity. Watch Pittwire in the coming days for interviews with more of the panel’s participants.