The Trump White House is on the verge of delivering a one-two punch to one of the most important health care programs in the United States: childhood immunizations.

The first punch would come from the Senate’s version of the American Health Care Act, which eliminates the Prevention and Public Health Fund (PPHF). The PPHF, which was created in 2010 as part of the Affordable Care Act, was originally intended to supplement several core public-health programs. During the past few years, however, the PPHF has evolved to be one of the most important government programs in support of vaccines. In fiscal 2016, for example, $324 million, or about 53 percent of immunization funding to the Centers for Disease Control and Prevention (CDC), came from the PPHF.

The second blow will come from the president’s proposed budget, which would reduce funds for the CDC to support vaccines, to $521 million in 2018 from $606 million in 2017. Most legislators have claimed that the president’s proposed budget is dead on arrival in Congress. Nonetheless, his budget makes clear the administration doesn’t value public health. Even if the final cuts are only a fraction of what is proposed, tens of millions of dollars will no longer be available for immunizations.

What would happen if the CDC’s immunization budget lost $100 million from the proposed budget and $324 million from the PPHF? One could expect the following:

• States will have less money to purchase vaccines.

• States will have less money to train personnel to administer vaccines.

• States will have less money to support the staff and technologies necessary to track immunization coverage.

• States will have less money to purchase cancer-preventing HPV vaccines for teens and pre-teens.

• The CDC will have a reduced capacity to respond to outbreaks of vaccine-preventable diseases, influenza pandemics, manmade disasters, and emerging threats like the Zika virus.

• The CDC will have less money to monitor vaccine safety.

While there is much to debate about the most efficient and effective ways to deliver health care to the American public, three things aren’t debatable: 1) Vaccines save lives, 2) Vaccines save money, and 3) Reduced support for vaccines will put children at unnecessary risk.

Before vaccines, Americans could expect that every year diphtheria would kill 15,000 people, mostly teenagers; rubella (German measles) would cause 20,000 babies to be born blind, deaf, or mentally disabled; pertussis (whooping cough) would kill 8,000 children, most of whom were less than 1 year old; and polio would permanently paralyze 15,000 children and kill 1,000. Because of vaccines, many of these diseases have been completely or virtually eliminated from the U.S. Smallpox—a disease estimated to have killed 500 million people—was eradicated by vaccines.

Further, for each dollar spent on childhood vaccines, the U.S. saves $10.10. During the past 23 years alone, vaccines have prevented 381 million illnesses, 855,000 deaths, and 24.5 million hospitalizations as well as saved $360 billion in direct costs and $1.65 trillion in societal costs (e.g., time lost from work).

Let’s presume that Congress eventually enacts the dramatic cuts in funding proposed by the Senate’s version of the AHCA and even a fraction of the cuts proposed by the president. The canary in the coalmine will be measles. Because measles is the most contagious vaccine-preventable disease, it will be the first to come back.

Before the measles vaccine was introduced in 1963, every year measles would infect about 4 million children, causing 48,000 to be hospitalized and 500 to die. Because of the vaccine, measles was eliminated from the United States in 2000. Recently, however, more parents have chosen not to vaccinate their children. As a result, a series of measles outbreaks have occurred in undervaccinated communities.

For example:

• In 2014, an outbreak of measles in an Amish community in Ohio affected more than 600 children.

• In 2015, an outbreak of measles starting in Southern California’s wealthy suburbs spread to 25 states and affected 189 children.

• Currently, an outbreak of measles in a Somali community in Minnesota has caused 76 children to suffer, again because their parents had chosen not to vaccinate them.

Not surprisingly, controlling outbreaks is expensive. The CDC estimates that it costs about $140,000 to contain each individual case of measles ($143.5 million since 2014).

Today, according to the CDC, about 1 percent of parents choose not to immunize their children. If this 1 percent were evenly distributed across the country, the measles virus wouldn’t spread because enough members of the community would be vaccinated, protecting those who aren’t vaccinated or can’t be vaccinated (so-called herd immunity). But parents who choose not to vaccinate their children aren’t spread out equally. Pockets of unimmunized children in Ohio or Southern California or Minnesota were the fertile ground for our most recent measles outbreaks.

Imagine, however, if the reason that children weren’t getting vaccinated wasn’t that parents had chosen not to vaccinate them but that they couldn’t afford to vaccinate them. And that instead of 1 percent of American parents choosing not to immunize their children, 5 or 10 or 15 percent weren’t able to immunize them. To prevent the measles virus from spreading, about 95 percent of children in a given community need to be immunized. If the nationwide immunization rates drop well below that figure, measles will be back with a vengeance. And when hundreds of cases of measles a year becomes thousands of cases, children will again start dying from measles.

On June 13, Donald Trump, in a meeting with republican senators, called the AHCA proposals “mean.” He could have added “dangerous.” Because the only thing that the AHCA and the proposed budget will make great again are the viruses and bacteria that routinely disabled, hospitalized, and killed our children.

Paul A. Offit is a professor of pediatrics at the Perelman School of Medicine at the University of Pennsylvania and the author of Deadly Choices: How the Anti-Vaccine Movement Threatens Us All (Basic Books, 2011).