Childhood vaccines: What research shows about their safety and potential side effects

Why Do We Have Side Effects To Vaccines?

Why Do We Have Side Effects to Vaccines?

At this point, everyone has read about the COVID vaccine, and I'm sure many of you are fully vaccinated by now. As more and more people become vaccinated, we're reading stories in the news about the "significant" side effects of the vaccines. About a third of everyone who gets the COVID vaccine has a side effect beyond just pain at the vaccine site. Most of these are "mild" (which in medical terms means "not hospitalized"), but they can feel very severe. These reactions have, understandably, made some people apprehensive to get vaccinated. However, mild side effects to vaccines are common and can be considered a positive reaction. But why do vaccines cause side effects?

Understanding Side Effects

First, to understand why we have side effects, we need to understand a little immunology. When you get sick from an infection, it's not the infection that makes you sick, it's your reaction to the infection that makes you sick. If your immune system detects an infection, it releases many compounds, such as interferon, interleukin, and tumor necrosis factor (TNF).

Source: The Image Library from the Centers for Disease Control and Prevention

These compounds rev up your immune system to fight off the infection. But they can also make you feel sick. They cause your body to mount a fever, which you can survive, but bacteria and viruses typically can't. In addition, these chemicals cause you to feel tired, achy, and nauseated, making you want to lie down and reserve your calories for fighting off the infection, rather than use your precious energy for digestion or exercise.

We're Talking About Practice?

Vaccines are designed to simulate an infection, which can also cause the release of these immune compounds. Immunizations are basically practice for your immune system. They work by preparing your immune system for a specific bacterial or viral infection by presenting an "antigen," which is a part of the infectious agent that triggers your immune system but cannot cause the disease. Once presented with an antigen, your body makes antibodies that match the antigen and "remember" if that infectious agent ever shows up again. In other words, vaccines are actually the safest and most natural way to fight infection, because they rely on your body's own defenses, rather than on medications.

Because vaccines use the same antigens found in bacteria and viruses, it's not uncommon to have similar symptoms after a vaccine as you would to the actual infection. For instance, tetanus infection causes painful muscle contractions; it's common to have a painful shoulder muscle for a few days after you get a tetanus shot. Influenza causes fever and fatigue, so these can be reactions to a flu shot, albeit in a milder form. The COVID vaccine can cause headache, fatigue, fever, and joint aches, which are common symptoms of COVID. This can explain the common misperception that vaccines can actually cause the illness they are designed to prevent.

The important point to remember is that a vaccine is supposed to cause an immune reaction; feeling ill after a vaccine can actually be a good sign. It implies that you are building immunity, and are having the desired response. Feeling a little sluggish for a few days means you are far less likely to get a more severe illness later on. This also explains why you might have a more notable reaction after a booster shot since you already have some immunity built from the first shot. However, if you don't get any symptoms after a vaccine, you still likely have immunity but are lucky enough not to feel side effects.

Side Effects May Include

There are rare cases where a side effect of a vaccine can be severe and dangerous, but these are extremely unlikely. For example, the rate of anaphylaxis due to the COVID vaccine is about one in 100,000, which is far less than your risk of becoming seriously ill from COVID itself. Also, there is a condition called Guillain-Barre, which only occurs in about one in a million. You're twice as likely to get hit by lightning than to get this condition from a vaccine.

It's important to remember that you are not immune for a few weeks after you complete a vaccine series, so continue to take precautions to prevent infection. Also, if you get severe symptoms, such as shortness of breath or high fever, or symptoms last for more than 2 to 3 days, you should contact your physician.

Benefits Outweigh the Risks

Unfortunately, these side effects often get more press than the benefits of the vaccine, which causes hesitance in some people. One case of a serious illness makes for good news, but thousands of people staying healthy does not. The rule of thumb in medicine is that the benefits of any action should outweigh the risks. The benefits of vaccines far outweigh the risks, possibly more than any other prevention or treatment we have ever developed. Vaccinations have essentially eliminated polio, smallpox, measles, mumps, and likely soon, chicken pox. They can also help prevent certain cancers, such as cervical and liver cancer, and, in the case of the flu vaccine, can prevent heart attacks and pneumonia.

Get your COVID vaccine when possible, and any others for which you might be eligible. And if you get some mild side effects, take some Tylenol and feel confident and encouraged because it likely means the vaccine is working. A little misery now can save you from a lot of misery later.

Is MMR Vaccine Safe For Kids? Dr. Nicole Saphier Addresses Concerns As Measles Cases Rise

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Measles is spreading in the southwestern U.S., as an outbreak in Texas has now crossed the border into New Mexico.

The Texas Department of State Health Services (DSHS) confirmed in an updated report Friday that there have been 90 measles cases identified since late January.

The New Mexico Department of Health (NMDOH) confirmed three cases just last week, bringing its total to eight.

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Texas DSHS reported that the majority of cases were mostly unvaccinated, school-aged children, which highlights the importance of vaccination.

The measles, mumps and rubella (MMR) vaccine is one of the most common childhood inoculations and has been a requirement for school attendance since its development in the 1970s.

One of the most common childhood inoculations — the measles, mumps and rubella (MMR) vaccine — has been a requirement for school attendance since its development in the 1970s. (iStock)

To address parents' concerns, Fox News medical contributor Dr. Nicole Saphier answered some frequently asked questions regarding the vaccine in a video for Fox News Digital. (See the video at the top of the article.)

People often ask why the three vaccines are combined, which Saphier said is simply for convenience.

"From a public health standpoint, if the goal is to vaccinate as many children as possible to reach that herd immunity and keep these infections at bay, again, parents are more likely to only bring their child to the pediatrician that one time," the doctor said.

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"And with a child, isn't it easier to give one injection as opposed to three separate injections?"

Saphier also addressed concerns about MMR vaccine side effects, including inflammatory reactions at the site of the injection, where the skin can become red and warm.

Kids can also have low-grade fevers and feel irritable or lethargic, which is "likely to happen" with any of the three individual vaccines.  (iStock)

Children can also have low-grade fevers and feel irritable or lethargic, which is "likely to happen" even with each individual vaccine – not just when the vaccines are combined.

"The reality is there are always side effects when it comes to any sort of healthcare intervention," she said in the video. "But with vaccines in particular, you can have more mild side effects, and there are some severe, more rare side effects that are well-documented."

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The potential for a link between autism and vaccinations has been a deterrent for many parents when choosing to vaccinate their children, but Saphier said the "overwhelming majority" of "good research" shows no causal link.

One of the largest studies, conducted in Denmark, found a lower risk of autism in more than 650,000 vaccinated children, the doctor noted.

The threat of a link between autism and vaccinations has been a deterrent for many parents, but the doctor said the "overwhelming majority" of "good research" shows no causal link. (iStock)

While the U.S. Has a higher incidence of autism compared to other countries, specifically Europe, the doctor revealed that European nations have higher rates of MMR vaccine uptake.

"Isn't it easier to give one injection as opposed to three separate injections?"

"The signs and symptoms [of autism] start to show around the time we're giving all these vaccines, so it makes sense to kind of think they may be related," she said. 

"And it made sense to do as much research as we can to make sure there isn't a link."

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"But I think we need to be looking really hard at our environment, what we're ingesting, the pollutants, the toxins, everything in big agriculture, big pharma, in our food industry and everything else."

Saphier suggested that a link to autism may be found after diving into the "harmful chemicals" consumed by Americans that other nations do not consume.

Dr. Saphier suggested looking into environmental factors that could increase autism risk.

The doctor also said that medical agencies — such as the Centers for Disease Control and Prevention (CDC) and the American Academy of Pediatrics — should be "less stringent" on vaccination schedules, leaving the decision to the parents.

"It should be a conversation between the doctor and the patient."

"If parents don't want to give these vaccines when their babies are so little, I think it's OK to have that conversation and let them wait until their child's a little bit older before they head off to kindergarten," said Saphier, who is a mother of three boys.

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"Because maybe at that time, you start to see signs of autism between about 1 to 3 years of age for the most part. So maybe let the parent get their child through that time, and if there aren't signs of autism, then maybe they'll feel better about … being able to vaccinate their children."

A doctor said she supports returning autonomy to parents when it comes to vaccines for children. (iStock)

"It should be a conversation between the doctor and the patient," she said.

"Unfortunately, during the COVID pandemic, the CDC and a lot of healthcare professionals really took away this conversation." 

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"By putting the COVID vaccine and booster for children in the same basket as MMR and some of the other vaccines, when it comes to children, that was the biggest mistake they could have ever [made]," Saphier continued. 

"That has caused more vaccine hesitancy and concern."

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Saphier expressed her hope that the Make America Healthy Again (MAHA) movement will help identify safety signals in vaccines, which will "give parents the confidence they need to continue with the vaccine programs, because they really can save lives."

Fox News Digital's Khloe Quill contributed reporting.

The Very Real Lifelong Side Effects Of Measles: The Stories

In 1957, just six years before a vaccine was released, Sarah R. And her cousin were infected with measles at the same time. Sarah, who now lives in Oakland, California, eventually recovered without major lasting effects. But her cousin, whom the family affectionately referred to as "Cotton" because of his platinum blond hair, lost both his hearing and eyesight. They were 6 years old.

The two cousins started feeling ill during one of their family's frequent visits together. Cotton soon went home, and Sarah continued to get sicker: Her fever spiked to more than 105 degrees. She was given a painful immune globulin injection, which contains antibodies and can sometimes reduce the severity of measles infection.

Despite the shot, Sarah became very ill, unable to leave her bed for two weeks. Her grandmother bought her a canary to cheer her up. "That bird saved my life," she says. Her high fever triggered seizures. She began hallucinating monsters and horrible creatures wandering her room. "I was absolutely terrified for hours at a time," she says. "I had dreams of them for years — scary, scary dreams."

Now 73, Sarah recovered without serious physical consequences, save for a heart murmur that's still present today. Cardiac issues can happen if the inflammation from an infection is severe enough to damage the heart muscle. (Sarah asked to be identified only by her first name to maintain anonymity as a former public figure.)

Measles can cause a splotchy rash all over the body.

Cotton was less fortunate. According to Sarah's family, his health went downhill quickly. He developed meningitis, or inflammation around the brain and spinal cord, and encephalitis, inflammation of the brain tissue itself. This caused him to lose his hearing, a common meningitis complication. It also affected his optic nerve, Sarah says. Barely in first grade, Cotton became both deaf and blind. "He had been a perfectly happy, healthy, bouncy, athletic little boy," Sarah recalls. "He was terrified of just about everything after that."

After about two years, Sarah saw Cotton again. "He mostly just touched my face and cried." Not long after that, Cotton was taken to be cared for in an institution, Sarah says. She never saw him again. "It affected me for life," she says.

And that's precisely what measles can do: affect you for life. Long-term side effects aren't widely reported or discussed, but they're real and range from mild to debilitating. 

Measles is a highly contagious viral disease that spreads through the air. Because of the success of measles vaccines, the disease was declared eradicated in the U.S. In 2000, though it remains widespread in other parts of the world. But it returned in March with an outbreak that began in largely unvaccinated communities in Texas and has since spread to 17 states, according to the World Health Organization. At last count, there were more than 800 cases and at least three deaths, the largest outbreak in all but one of the last 25 years.

Because it's been a quarter century since the last large outbreak, some people believe that measles is comparable to the flu or other common infections. Nothing could be further from the truth, health experts say.

Most Americans who remember living with measles are in their 60s or older. They remember what the world looked like before the vaccine. The CDC estimates that measles infected as many as 3 million to 4 million people in the U.S. Each year. Many escaped without major consequences, but many others did not. Every year, about 500 people died, tens of thousands were hospitalized, and about 1,000 developed encephalitis.

"The complication rates are pretty high, when you think about it," says Jeffrey Kahn, MD, PhD, chief of the Division of Pediatric Infectious Disease at the University of Texas Southwestern Medical Center in Dallas. The death rate is about 1 to 3 in 1,000. About 1 in 5 people end up hospitalized, mostly children under 5 years old. In 2024, more than half of children under 5 with measles were hospitalized.

Measles also wipes out your immune system, including your adaptive natural immunity from other diseases, essentially unvaccinating you against pathogens you've already encountered, Khan adds. It opens you up to other diseases, including the flu; respiratory syncytial virus, or RSV; and severe pneumonia, any of which can be fatal. It also makes you vulnerable to dangerous bacterial infections, such as bacterial meningitis, the form most likely to cause hearing loss.

LaDonna Qualtieri, who lives in Oakland, had hearing loss after getting measles as a newborn in 1961. After her infection, doctors discovered she was severely hard of hearing in her left ear as a result of nerve damage. "As a child I always felt like I wasn't quite getting something," Qualtieri says. "I was exhausted, I think, from trying to hear everything."

LaDonna Qualtieri as a child in 1967.

Qualtieri also had vision trouble, which she suspects was related to her infection because she has no family history of poor eyesight. Indeed, measles is a leading cause of childhood blindness in less developed countries without good vaccine access. "In the car, I would always see these big, blurry, red and green objects. I thought they were Christmas decorations," Qualtieri recalls. "It wasn't until I got my first pair of glasses, and we were driving home from the optometrist, that I could see they were traffic lights."

Qualtieri's hearing loss also affected her career. Born with a love and a talent for mechanics, she applied to her dream job as an apprentice operating engineer in 1985. "I always wanted to be in a union so badly," she says. But they sent her a letter of rejection on the basis of her hearing loss. She was crushed. "I remember getting that letter and just crying." She spent 25 years making a living largely in low-paying, heavy labor jobs. 

Encephalitis can also have significant mental and emotional consequences. In March 1960, 6-year-old Emmi Herman of New York watched her older sister, Marcie, get measles from a classmate. Marcie, then 9 years old, became sick quickly and was rushed to the hospital. She had developed encephalitis. She fell into a coma for more than five weeks, Herman says, and had irreversible brain damage.

Around Passover in April, Marcie finally came home. "She survived, but she was a different Marcie," Herman recalls. Her movements and social cues had become strange. Her laugh had become exaggerated. She often had abrupt mood changes. She'd been a great dancer, but now she struggled with balance. A gifted pianist, she now made frequent mistakes. She became easily frustrated and got sick often. She'd been popular, but now she struggled to make friends. "She was ostracized," Herman says, emotion entering her voice. "She ate her lunch in the bathroom." As she got older, she would get herself into unsafe situations because of poor judgment.

Emmi Herman (left) and Marcie Cline (right).

Marcie grew up and eventually married, becoming Marcie Cline. She divorced shortly thereafter, but retained her married name, Cline. Over time, Cline developed severe mental illness. She began hoarding, living in a "garbage-strewn apartment," and eventually received a diagnosis of schizophrenia. But Herman believes the diagnosis was not complete because Cline refused most mental health care, becoming agitated at the mention of psychological illness. They tried family therapy, but Cline stormed out of every session. "She claimed she was not disabled," Herman says. "There was nothing wrong with her, and we were all crazy."

After speaking with psychologists, Herman came to suspect that Marcie had developed anosognosia, a condition linked to brain damage that causes people to be unaware of their condition. This lack of self-awareness made it almost impossible to get Marcie Herman adequate care. She allowed most medical care, "but when it came to her mental health, that's where we lost her," Emmi Herman says.

Herman was eventually able to get Cline into short-term secure psychiatric care at Cornell Weill Medicine and later into an assisted living facility in Yonkers, New York, where she could finally make strides towards feeling more stable. "There was a big difference in the help she got later on," Herman says. "But of course, it didn't really" make up for the years before.

In August 2020, just after her 70th birthday, Cline died of a major stroke following a bout with COVID-19.

It's rare for measles to affect the brain, but that complication is not as rare as one might think. "Encephalitis usually occurs in about 0.1% to 1% of measles cases," or 1 to 10 in 1,000 cases, Kahn says. That's roughly the same odds as having identical twins (about 4 in 1,000 births) or getting your car stolen in the U.S. (about 3 in 1,000). 

One serious form of encephalitis, called subacute sclerosing panencephalitis, happens when a natural measles infection reactivates in the brain, typically several years later. It affects between 1 and 28 people per 100,000 measles cases. But in unvaccinated infants younger than 15 months, that ratio is much higher: as many as 1 in 600, according to a study by the American Academy of Pediatrics. It is almost always fatal. The risk of SSPE after vaccination with the weakened measles virus is almost nonexistent.

When the measles vaccine was introduced in 1963, it sent measles infections crashing down to about 22,000 cases in 1968. As more people got vaccinated, that number kept shrinking. "We hit a low in this country in 2004" of 37 cases, Kahn says. "Give me an example of a greater accomplishment in medicine than that." The vaccine was so effective that many doctors today don't even recognize the disease when they see it, Kahn says.

Out of hundreds of millions of vaccinations worldwide, there have been no known deaths in healthy people caused by the measles, mumps, and rubella vaccine, commonly called the MMR vaccine. There have been exceedingly rare serious allergic reactions reported, about 1 in 1 million doses. The vaccine can make you sick if you're severely immunocompromised. But overall, decades of experience with the vaccine have proven it to be quite safe.

Herman, Qualtieri, and Sarah are now staunch advocates for measles vaccination, having lived with the dire consequences that can come from this preventable disease. 

"We felt so alone in 1960," Herman says. "But now when I write Marcie's story, I get responses from readers who had [measles], or have a relative who had it, and so many of the issues are so similar to what my family went through. Those kinds of things stay with you for your whole life."

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