If there’s one thing parents and children both dread about going to the pediatrician, it’s those routine shots. Your kids hate them because of the ouch factor, while you may be dealing with your own apprehensions about how safe vaccines are and whether they’re truly necessary. But the real danger to children is having misinformed parents, particularly if that misinformation leads parents not to immunize kids, experts say. After all, kids who aren’t vaccinated are much more likely than vaccinated kids to develop measles, whooping cough and other diseases.

A 2016 survey of pediatricians, published in the journal Pediatrics, found that the proportion of pediatricians reporting vaccine refusals rose from 75 percent in 2006 to 87 percent in 2013 — and they believe it’s because these parents increasingly believe that immunizations are unnecessary.

Where does this mistrust of vaccines come from? “At the heart of this is: People aren’t scared of the diseases [the vaccines protect against] because they don’t see diseases like polio or Haemophilus influenzae type b (or Hib),” says Dr. Paul Offit, professor of pediatrics in the division of infectious diseases and director of the Vaccine Education Center at the Children’s Hospital of Philadelphia. “To some extent, vaccines are victims of their own success, and people are scared by erroneous information that they see on the internet from anti-vaccine groups. That’s the one-two punch.”

[See: 10 Concerns Parents Have About Their Kids’ Health.]

Here’s a look at four common fears parents have about children’s vaccines, along with the truths behind them:

The Fear: The measles, mumps and rubella vaccine vaccine is linked with autism.

The Facts: This theory emerged in 1998 when British researcher Andrew Wakefield and his colleagues published a paper in the medical journal the Lancet, describing several previously normal children who developed gastrointestinal diseases and developmental disorders after getting the MMR vaccine. The researchers suggested the MMR vaccine may have been responsible. In February 2010, the journal completely retracted the paper and discredited the claim. But fears about the proposed link will not die, as evidenced by the January 2017 meeting between President Donald Trump and Robert F. Kennedy Jr. to discuss the issue. These fears are “not grounded in fact,” Offit says. “Seventeen different groups of researchers on three different continents have looked at the scientific evidence and concluded that the MMR vaccine neither causes nor prevents autism.”

Nevertheless, some parents (and politicians) cling to this perception, largely because of an issue of timing: The MMR vaccine is generally given to children between 12 and 18 months of age, and it’s shortly after that window that signs of autism are often first recognized. At that point, it’s hard to convince parents that if their child had a vaccine and something adverse happens a short while later that they’re not related, Offit says. “We’re always looking for causes, and vaccines are an easy scapegoat. But we really don’t know what causes autism.”

[Read: Why Adults Shouldn’t Skip Vaccines.]

The Fear: Vaccines can be blamed for the rise in childhood asthma and allergies, including food allergies.

The Facts: The theory is based on what’s called “the hygiene hypothesis,” or the notion that if young kids don’t get sick with infections early in life, they have a higher risk of developing allergic diseases later. The idea is that since the body’s immune system has nothing to guard against, it responds to harmless irritants by mounting an allergic response, explains Dr. Ari Brown, a pediatrician in Austin, Texas, and co-author of “Baby 411: Clear Answers & Smart Advice for Your Baby’s First Year.” “While the hygiene hypothesis is intriguing, it doesn’t play out with vaccines because vaccines don’t keep kids from getting their share of colds, stomach viruses, sore throat viruses and other infections.” The truth is, no one exactly knows why some kids develop asthma, allergies or autoimmune diseases — aside from a possible a genetic component — while others don’t. But there’s no evidence that vaccines play any role whatsoever.

The Fear: Too many vaccines given in too short a time weaken a child’s immune system.

The Facts: It’s true that young kids now receive more vaccines than ever. “Fifty years ago, they received five vaccines routinely,” Offit notes, “whereas today children receive 14 different vaccines by age 2.” There’s no question that it’s hard for parents to stand by and watch multiple syringes being injected into their child’s small body. But research has found that infants and young children have an enormous capacity to respond to multiple vaccines, and by providing protection against various bacterial and viral infections, vaccines prevent weakening of the immune system as well as secondary infections that can occur with these illnesses, Brown says.

It helps to “think of the immune system as a computer,” Brown adds. “Every time you vaccinate, you give the immune system a new memory chip which makes it more powerful. So when the body sees that particular germ, it is prepared to attack.” In other words, she says, “vaccines strengthen the immune system.”

[Read: 4 Options for Patients Afraid of Needles.]

The Fear: The risk of your child having an adverse reaction to a vaccine isn’t worth taking for a mild illness like chickenpox.

The Facts: For most adults, chickenpox was a mild illness and a childhood rite of passage, which is why it took a while for the varicella (or chickenpox) vaccine to gain widespread acceptance, even among pediatricians, notes Dr. Louis Z. Cooper, professor emeritus of pediatrics at Columbia University in New York City and a past president of the American Academy of Pediatrics. But it can be a serious illness. Before the vaccine was approved in 1995, more than 10,000 people were hospitalized for chickenpox and 100 died each year, Offit notes. That’s because chickenpox can lead to complications such as bacterial skin infections, encephalitis (brain swelling) and pneumonia. “I personally cared for a child who had chickenpox and developed a secondary strep skin infection from scratching the lesions,” Brown says. “The infection invaded her bloodstream and every major organ. She died 90 minutes after arriving in the emergency room.” Tragedies like this can be prevented with the vaccine.

Fortunately, most children in the U.S. “are pretty well protected [from these diseases] because the average family does the right thing [by vaccinating their children],” Cooper says. This leads to what’s called “herd immunity,” protection from the spread of a contagious illness because a critical proportion of the population has been vaccinated against it. “The goal is to make getting vaccines over time the social norm,” Cooper says, “so we can protect even more children.”

More from U.S. News

4 Options for Patients Afraid of Needles

Why Adults Shouldn’t Skip Vaccines

10 Concerns Parents Have About Their Kids’ Health

Vaccine Fears: What Parents Need to Know About the Myths and Facts originally appeared on usnews.com