The best and the worst thing about vaccination, pediatrician Dr. Adam Ratner says, is that it “makes nothing happen.”

A child successfully inoculated against a vaccine-preventable disease — the measles, let’s say, to name the most infectious of them all — doesn’t fall sick with that condition, doesn’t miss school, doesn’t go to the hospital. They don’t suffer life-changing complications. They don’t die prematurely.

This absence of action can make it easy to forget the role vaccination played in keeping that child healthy. It can be easy to confuse a society that has responsibly controlled measles for a society that is no longer threatened by measles.

These moments of complacency are when vaccine rates dip and illnesses long kept at bay by effective public health programs begin creeping back, Ratner said.

And almost always, the first preventable illness to elbow its way back onto the scene is measles — a highly contagious virus that’s stunningly adept at exploiting our social and physical weaknesses.

Measles “is the thing we see first when public health starts to falter,” Ratner said recently from his office in New York City.

“It’s not that humans aren’t susceptible to these diseases, or that Americans are somehow magically protected against these things that used to kill lots of us,” he said. “They can come back. And they will.”

Ratner, who heads the pediatric infectious disease unit at NYU Langone’s Hassenfeld Children’s Hospital, tracks the history of the virus and its vaccination in his new book “Booster Shots: The Urgent Lessons of Measles and the Uncertain Future of Children’s Health.”

Ratner began drafting the book after the 2018-19 measles outbreak in New York City, in which he treated some of the roughly 650 people who fell ill.

He continued writing during the COVID-19 pandemic, as debates over trust in public health turned bitter and rancorous.

It publishes as the Senate seems poised to confirm President Trump’s nominee, Robert F. Kennedy Jr., a prominent vaccine critic, as the next health secretary.

“He’s written a book that, sadly, couldn’t be better timed,” said Dr. Paul Offit, a virologist and immunologist at the University of Pennsylvania.

“As people become less and less comfortable about vaccines, as they become more and more cynical about vaccines, immunization rates are starting to decline. That’s already happening,” said Offit, who runs the Vaccine Education Center at the Children’s Hospital of Philadelphia, where Ratner was a fellow. “Measles is the canary in the coal mine because it is the most contagious, far and away, of the vaccine-preventable diseases.”

In the book, which publishes Tuesday, Ratner describes a virus with an “unmatched ability to spread from person to person” that once regularly claimed the lives of at least 400 U.S. children per year.

Although a safe, cheap and effective vaccine to prevent most cases has been available “since well before the moon landing,” Ratner writes, measles has proved remarkably effective at undermining the collective effort required to keep populations healthy. The vaccine is to an extent a chronic victim of its own success.

“The better that we get at using the measles vaccine, the lower the case rates go. The lower the rates, the less people think about measles,” Ratner writes. Parents may wonder why it’s worth giving children an injection to prevent a disease that no one ever gets. Politicians may question whether vaccination drives are worth funding.

“When we forget,” Ratner writes, “measles thrives.”

Before the measles vaccine’s introduction in 1963, nearly all U.S. children contracted it before their 15th birthday, resulting in up to 4 million cases each year, according to the U.S. Centers for Disease Control. An estimated 48,000 people were hospitalized annually with serious complications such as encephalitis.

The measles vaccine, which in 1971 was combined with inoculations for mumps and rubella, is widely considered a triumph of public health. Since 2000, the MMR vaccine has saved an estimated 60.3 million lives.

There were 284 cases of measles in the U.S. last year, 40% of which required hospitalization. A full 96% of cases were in people who were unvaccinated, did not finish their MMR series or whose vaccine status was not known, according to the CDC.

Yet total eradication remains elusive, and control over the virus is precarious, Ratner warns.

A population achieves herd immunity from measles when more than 95% of people are fully vaccinated. Last year’s cohort of kindergartners failed to reach that target, with only 92.7% completing their measles, mumps and rubella vaccine series. Uptake rates among kindergartners for all vaccines declined from the year before.

Globally, armed conflict and social upheavals can upend vaccination goals. But it doesn’t require violence to derail public health goals, Ratner writes.

“Even in wealthy nations, when anti-vaccine charlatans and pseudoscience peddlers thrive, when funding to vaccination programs is cut, when well-meaning parents do not learn how to tell reliable information from its opposite and thus fail to vaccinate their children, measles is often the first sign,” Ratner writes. “It is also a sure indication that other problems are not far behind.”

Ratner finished the book well before the 2024 election and Kennedy’s subsequent elevation.

Kennedy was for several years chair of Children’s Health Defense, a nonprofit that falsely claims childhood vaccines cause autism, and has a well-documented history of publicly questioning the science behind the shots. He described the health effects of vaccines as a “holocaust” in 2015, for which he later apologized.

During confirmation hearings before two Senate committees last month, Kennedy said that his views on vaccines have been mischaracterized, and that he supported the childhood vaccination schedule.

The prospect of an outspoken vaccine critic heading the Department of Health and Human Services “is horrifying,” Ratner said in a recent interview. “I can’t imagine a worse situation for public health in the country.” (His views on Kennedy are solely his own, he noted, and don’t represent the position of his hospital.)

“People are trying to make political points, and people are angry about lots of things. But the problem is that the fallout is real children,” Ratner said. “When we can’t get new vaccines licensed, when we have to fight to keep the ones that are already licensed on a recommended schedule, it is children . . . that are going to suffer.”

There have been skeptics of inoculation for as long as humans have been experimenting with it. Ratner notes that when Puritan minister Cotton Mather advocated publicly in 1721 for variolation, an early form of smallpox vaccination, a grenade came crashing through his window bearing a note: “You Dog, Dam you: I’ll inoculate you with this, with a Pox to you.”

Hanging in his office is a framed vintage poster the CDC commissioned in the late 1970s, when the Vietnam War and Watergate had shaken the public’s faith in government authorities.

Above the “Star Wars” characters R2-D2 and C-3PO, the poster asks: “Parents of Earth, Are Your Children Fully Immunized?” It’s a reminder that vaccine hesitancy has been with us for decades, he says, and that accessible, trusted messengers can make a difference. The stakes could hardly be higher.

“Adam’s thesis is spot on: Public trust in science and public health is at an all-time low,” said Jay Vornhagen, a microbiologist and immunologist at Indiana University School of Medicine.

If we don’t find ways to rebuild that trust — if the medical and public health communities don’t reconnect with the public, and vice versa —more people, mostly children, will suffer,” Vornhagen said. “We need to come together as a community, to see the humanity in one another, and to make choices that extend beyond ourselves.”