President Donald Trump and his administration are increasingly criticizing the use of vaccines on children, even though vaccines have kept millions of children healthy while also improving global public health.

The focus on vaccines comes as the government monitors the biggest measles outbreak in the United States in more than 30 years and increasing cases of whooping cough and flu deaths in children.

Some of the president’s claims in recent weeks — that vaccines cause autism, or that some combination shots given to prevent multiple diseases should be separated — are not rooted in fact or science. During a September 22 news conference, Trump openly speculated about why children receive so many shots.

“They pump so much stuff into those beautiful little babies. It’s a disgrace. I don’t see it. I don’t, I think it has, I think it’s very bad,” the president said during remarks where he also warned pregnant people to avoid pain-relief medication like Tylenol, claiming that it causes autism despite research refuting the connection. “They’re pumping, it looks like they’re pumping into a horse. You have a little child, little fragile child, and you get a vat of 80 different vaccines, I guess. Eighty different blends, and they pump it in.”

Health and Human Services Secretary Robert F. Kennedy Jr., an anti-vaccine activist who is playing a central role in vaccine policy despite a lack of relevant experience, gave a different estimate during a Senate hearing on September 4.

“When I was a kid, I got three vaccines, I was fully compliant,” Kennedy said. “Today’s children have to get between 69 and 92 vaccines in order to be fully compliant, between maternity and 18 years.” 

These figures are conflated and need context, medical experts say. Here’s what to know about the childhood vaccine schedule.

What is the childhood vaccine schedule, and why do we need one?

The childhood vaccine schedule, as it’s known in the United States, is a series of recommended vaccine shots for children that have been approved by medical professionals and the federal government. The vaccines, administered throughout childhood but primarily in the first years of life, protect children from diseases that used to be more common — like polio and diphtheria. The schedule is also used by insurance companies to determine which vaccines they will pay for.

Following the schedule is especially important for young children because their immune systems are still developing and they’re more susceptible to infection. 

Before the widespread introduction of vaccines, children were infected with more diseases that caused illness, long-term chronic ailments and sometimes death. Children who follow the vaccine schedule are less likely to become seriously infected by certain diseases, and they also create herd immunity for others who are unable to be vaccinated because of compromised immune systems.

Has the schedule changed? 

Yes. The medical community has recommended adding more vaccines to the schedule over time. But the science behind some vaccines — their ingredients, effectiveness and the shots necessary to complete a series — has improved.

The American Academy of Pediatrics, the trusted medical organization of pediatricians that was founded nearly 100 years ago, began making vaccine requirements in the late 1930s through a pamphlet with a red cover known as its “Red Book.” At the time, vaccines were available for only a handful of diseases: smallpox, diphtheria, tetanus and pertussis (whooping cough).

Over time, more vaccines were developed: The polio vaccine was introduced in the 1950s. Separate vaccines for measles, mumps and rubella were made available during the 1960s before a combination shot was introduced in the early 1970s.

During this time, doctors and researchers discussed the need for more formal vaccine guidelines. In 1964, a government-backed panel of experts, known as the Advisory Committee on Immunization Practices, or ACIP, was formed. It is housed under the Centers for Disease Control and Prevention.

For decades, AAP and ACIP issued separate but similar vaccine schedules for children. The groups, along with the American Academy of Family Physicians (AAFP) approved a single vaccine schedule that became effective in 1995.

New shots have been added periodically to the unified schedule: The varicella (chickenpox) vaccine was added in the mid-1990s; the rotavirus vaccine was added and revised between 1998 and 2008; the hepatitis A vaccine was added in 2000; and the pneumococcal vaccine was added in 2001. 

Kennedy politicized ACIP this summer by replacing all its members, and some of the new members do not have relevant experience in vaccine safety or policy. AAP, which had still been issuing standalone vaccine recommendations, is highlighting its work and not ACIP’s.

When Kennedy says he was vaccine compliant after just a handful of shots, he’s leaving out the fact that children back then got sick more often, said Dr. Paul Offit, director of the Vaccine Education Center at the Children’s Hospital of Philadelphia. This was a time before a vaccine to prevent measles, which at the time caused roughly 50,000 hospitalizations in children. Vaccination also didn’t exist for rubella, which at the time caused about 20,000 cases of congenital birth defects. Even chickenpox caused more than 10,000 hospitalizations before a vaccine was introduced.

“We live longer, better, safer lives because of those vaccines that weren’t available for Robert F. Kennedy Jr. and I when we were little boys in the 1950s,” Offit said.

Why are there so many vaccines on the schedule? And are there that many shots?

The vaccines listed on the current schedule help protect against more than 15 potentially serious diseases. The CDC lists each disease here.

Since some vaccines require multiple shots, that can add up. The polio vaccine requires four doses between infancy and 6 years old. The pneumococcal vaccine also has four shots in its series before age 2. The combination diphtheria, tetanus and acellular pertussis (DTaP) vaccine is five shots over several years.

By one estimate, children receive a little over 30 vaccine doses by the time they turn 18. That does not include annual immunization for the flu or COVID-19. People may choose to get those shots throughout adulthood.

That is more vaccines than in the past, but that is only because new vaccines have been developed to help prevent more diseases.

Dr. David Hill, a pediatrician in North Carolina and an official representative for AAP, noted the medical breakthrough of the pneumococcal vaccine that was added to the childhood vaccine schedule during his first years of practicing medicine. That vaccine helps block a serious bacteria that can cause multiple infections in the body

“It used to be that kids were in all the time with severe ear infections, sinus infections — we had to worry about those infections turning into meningitis if they got bad or were uncontrolled,” he said. “And I watched the number of ear infections that I would treat plummet, and the severity go down dramatically.”

Hill also noted the antibody shot for the respiratory syncytial virus, also known as RSV, that is given to pregnant people or newborns and has been available for only a few years. Emerging research shows they are safe and effective.

“I can tell you that RSV was just the bane of our existence all winter long in pediatric hospital medicine,” he said. “Our floors were inundated with babies who were having difficulty breathing, and just last year these protective efforts were fully rolled out, and it’s been a dramatic difference.”

Is there a cumulative impact for a child getting so many vaccines?

No. Vaccines are thoroughly tested for safety, including alongside one another to ensure they can be administered together. 

This topic is at the crux of Trump’s framing about the safety of childhood vaccines, since children sometimes receive multiple vaccine shots during early wellness check-ups. That may worry some parents about whether so many shots can overwhelm a child’s immune system. But research shows no cumulative impact on children.

Hill said parents should think about this through the lens of antigens, the part of viruses and bacteria that induce immune responses in the body. They are often the key ingredient in vaccines aimed at preparing the body for potential infection. The number of antigens in vaccines has decreased since the 1960s. So even though children may be getting more shots than before, they’re getting less of an antigen load compared with a few decades ago.

“Say your child gets a cold, they’re getting thousands of antigens when they get that cold. If your child drops a chocolate-covered raisin on the floor and picks it up and eats it, thousands of antigens. The dog licks their face, tons of antigens. They go to day care, countless antigens,” Hill said. “The entire vaccine series today carries fewer than 300 antigens. So in terms of what the immune system is capable of responding to, it is a drop in the bucket. It is just negligible when you compare it to the number of antigens that the immune system responds to over the daily course of life.”

Offit put it another way: “It’s not the number of shots that matters. It’s the number of immunological components in those shots that matters.” 

How does the United States compare to other countries when it comes to the number of vaccines that kids take?

Vaccine mandates and recommendations for children vary broadly around the world, and many are linked to school entry. While there is no global schedule standard for childhood vaccines, the World Health Organization tracks how countries aim to address the same vaccine-preventable diseases.

Some countries recommend fewer vaccine shots. The reasons vary: Access, finances, universal health care policies and vaccine manufacturers’ capacity all play a role in how governments set their policies.

Offit said one of the reasons the United States may have more vaccinations on its schedule — not just for young children, but older ones — is because it has been willing to invest in public health like supporting vaccine use. The British government just recently began recommending the chickpox vaccine, decades after the United States and other countries. Separately, while other countries do not recommend the human papillomavirus (HPV) vaccine, the United States added it to its vaccine schedule for older children and teens. Rates of cervical cancer in the United States have dropped.  

“Other countries choose not to do that,” Offit said. “The better question is, ‘Why don’t they do it?’ Not, ‘Why do we do it?’”  

What vaccines are needed for school?

Participation in public settings like day cares and schools often include vaccine requirements (unless there is an allowable exemption) because infectious diseases can spread easily in group settings. Certain jobs also require immunization records. States have different laws and rules for vaccine mandates.

What’s the risk of delaying or skipping certain vaccines?

More than 1 in 6 children in the United States begin but do not complete all vaccines that require multiple doses. Often that is because of access to health care, but some parents also choose to ignore the recommendations or delay certain vaccines.

Doctors do not recommend that parents skip or delay shots, since vaccines on the schedule have been timed to when a child’s immune system is most susceptible to certain diseases but also when that immune system is mature enough to respond to a vaccine. For example, ​​children are encouraged to complete the rotavirus vaccine series by six months of age because rotavirus is a common disease between six and 24 months of age.

“Children are vaccinated at certain ages because you want to make sure they’re immune and protected at a time when they would likely develop those diseases,” Offit said.

Many babies are born with maternal antibodies in their bloodstream, but that protection wanes as a child ages — which is why eliciting an infant’s own immune response is important.

“A delayed vaccine schedule only increases the period of time during which you’re susceptible to these preventable illnesses, with no benefit,” Offit added.

Do vaccines cause autism?

No, they do not. It’s a longtime debunked rumor that picked up steam in the late 1990s when a now-retracted research paper concluded that children who received the combination measles-mumps-rubella (MMR) shot later developed autism — despite no robust scientific proof. Several studies since then have shown no association between vaccines and autism. The MMR vaccine is also safe and effective.

How do we know that vaccines are safe?

Vaccines are tested during multiple phases of what’s known as clinical trials. In the United States, a vaccine product must pass safety standards before it can be approved for use and made available to the public. A vaccine that’s been added to the childhood vaccine schedule continues to be monitored afterward in case its use needs to be revised.

While vaccines can cause side effects — primarily some soreness and a mild fever — doctors are more concerned with the impact of a person becoming infected with a vaccine-preventable disease. Serious side effects are extremely rare, but if someone believes they or a child were harmed by a vaccine, there is also a legal mechanism to file a claim.