Of all the public health advances over the past century, I’m hard pressed to think of a bigger success story than routine childhood vaccinations. Every year, they save the lives of about 4 million children worldwide and prevent serious, potentially disabling illnesses in many more. Vaccinations have been so effective, in fact, that parents of young kids today have no memory of once-common childhood scourges like measles, diphtheria, and polio.
That, ironically, may be fueling a problem. A growing number of parents are becoming susceptible to vaccine “misinformation”—which takes different forms but always comes back to the outlandish claim that vaccines carry more risks than benefits. And it’s having real consequences: Childhood vaccination rates are dipping nationally, while the percentage of parents claiming vaccine exemptions for their children is on the rise, according to the Centers for Disease Control and Prevention (CDC). In some areas of the U.S., they’ve now fallen below the level necessary to sustain “herd immunity”—where enough people in a community are vaccinated against a disease to prevent its spread and help protect those who are unvaccinated (including babies and toddlers too young to have received all of their own immunizations).
This troubling trend started several years ago, with the pandemic, and it only picked up speed in the 2023–24 school year. And, with a vaccine cynic now confirmed as one of the nation’s top health officials, the future looks grim. Robert F. Kennedy, Jr., has promoted the long-standing myth that vaccines cause autism, sown doubts about the safety of vaccine ingredients, and published a book that portrayed Dr. Anthony Fauci, former director of the National Institute of Allergy and Infectious Diseases, as a shill of the pharmaceutical industry. Meanwhile, a lawyer and advisor to RFK Jr., Aaron Siri, has long sought to block the use of various vaccines: In 2022, he petitioned the U.S. Food and Drug Administration to revoke its approval of the polio vaccine—one of the most effective vaccines ever developed.
If that sounds like madness to you, I agree. I remember the dread that polio caused before we had a vaccine. Like many kids, I wasn’t allowed to go to public swimming pools because my parents worried that I would contract polio there. When I was about five years old, I woke up one morning with a stiff neck, and my mother immediately panicked, thinking it was polio. Luckily, it was just garden-variety neck pain, but all these years later I vividly remember my mother’s fear.
Again, though, many Americans lack those memories. So it’s worth looking back at the monumental achievement of polio vaccination and considering the potential dire outcomes of any significant dropoff in vaccination rates.
Polio is a highly contagious viral infection that, most often, causes no obvious symptoms. While that’s good news for those unaffected individuals, it also means that they can go about their usual lives, unknowingly spreading the virus to others. About one-quarter of people infected with poliovirus do fall ill, usually with flu-like symptoms such as fever, fatigue, headache, and nausea/vomiting. A portion of those people develop the dreaded complications of polio, including meningitis (inflammation of the covering of the spinal cord and/or brain) and paralysis. Paralytic polio can leave people with permanent disabilities or prove fatal if it impairs muscles involved in breathing. By the 1950s, polio was paralyzing or killing more than half a million people—mostly children—each year, according to the World Health Organization.
The U.S. saw a string of increasingly large polio outbreaks from the late 1940s through the early 1950s. During the worst, in 1952, over 20,000 Americans developed paralytic polio and more than 3,000 died. Hospitals were equipped with “iron lungs,” the large artificial respirators invented to treat polio patients who could no longer breathe on their own. A cousin of mine who I adored contracted polio when he was six and ended up in an iron lung for a few weeks. Fortunately, he improved to the extent that he could breathe on his own—but he was never able to move his arms again.
So in 1955, when the world’s first polio vaccine became available, parents lined their children up to get it. That vaccine, developed by U.S. physician Jonas Salk, inoculated recipients by exposing them to an inactivated, or “killed,” form of poliovirus. Dr. Salk first tested the vaccine on himself and his family in 1953, and then one year later, in studies of over 1 million children.
Within a year of the vaccine’s licensing in the U.S., polio cases dropped by half, and kept falling in the ensuing years. By 1979, polio was eliminated in the U.S.—meaning vaccination stopped the spread of “wild” poliovirus (naturally occurring strains that circulate in the environment). Today, nearly every country in the world has eliminated polio, thanks to vaccination.
Unfortunately, though, polio resurgence remains an ongoing threat. Wild poliovirus has not been eliminated in two countries (Afghanistan and Pakistan), so any unvaccinated person who comes in contact with the virus there, or through travel to or from those countries, can become infected and transmit it to others. Beyond that, wild poliovirus is not the only form that can cause disease; in rare cases, polio can be related to a second type of vaccine—the oral polio vaccine. That vaccine, given by drops into the mouth, was developed several years after the Salk vaccine and uses a weakened, rather than killed, form of poliovirus. Many low- and middle-income countries rely on the oral vaccine because it’s cheap and easy to administer. However, the weakened poliovirus is shed in children’s feces after vaccination, and it’s possible for that virus to spread in communities and eventually mutate to a disease-causing form that can sicken people who are not immunized.
Because of that rare risk, the U.S. stopped using the oral polio vaccine 25 years ago. But, just like wild poliovirus, mutated poliovirus strains that originate from the oral vaccine can be spread through travel. We saw that scenario play out in 2022, when an unvaccinated young man in New York State fell ill with paralytic polio. Testing showed that he had been infected with a poliovirus strain originating from the oral vaccine, and the same strain was later detected in sewage samples from the man’s resident county and some others nearby. Had he received his routine polio vaccination as a child, he would have been protected.
To be sure, it’s highly unlikely that the FDA will pull our current polio vaccine from the market, no matter who is in the White House. However, having vaccine cynics in places of authority can do damage in other ways. The Trump administration could, for example, continue to foment public distrust of vaccines, or support efforts in some states that would allow more parents to exempt their children from required immunizations. It could also interfere with the FDA and CDC approval processes for other vaccines. I worry that if current trends in our national vaccination rates continue, childhood diseases that were once vanquished, or largely contained, could come roaring back.
It’s more important than ever to remember why we vaccinate.
