Vaccines Print Facts About Vaccines, Vaccine Ingredients, and Vaccine Safety By Robyn Correll, MPH Updated July 02, 2019 Medically reviewed by Richard N. Fogoros, MD More in Prevention & Treatment Vaccines Healthy Aging First Aid Occupational Therapy Holistic Health Surgery Making informed choices about the health and the health of your family can be difficult, especially when there is a lot of misinformation out there. Social media sites and websites are full of vaccine myths and conspiracy theories designed to mislead parents or scare them away from vaccinating their children. But vaccinating is one of the most important steps families can take not only to protect themselves from diseases like measles or polio but also their entire community. Knowing the facts about the safety and effectiveness of vaccines and vaccine ingredients can help you make the best choice for you and your family. Practice Talking to Someone Skeptical About Vaccines 1 Vaccines Work Fewer things have had as much of an impact on public health as vaccines. Before widespread vaccination, diseases like diphtheria and whooping cough killed thousands of people a year. Those who survived were sometimes left with lifelong disabilities. While good hygiene and antibiotics have helped to dampen the harm from such diseases, vaccines are the primary reason cases of rubella and polio are now virtually unheard of in the United States and around the world. Vaccines have done a lot to prevent diseases like measles and meningitis, but just like seat belts or life jackets, they aren’t 100 percent effective. Some individuals who get vaccinated won’t develop enough protection to prevent them from getting sick. When vaccinated individuals do get infected, however, they are much less likely to die than those who never received the vaccine. 2 Vaccines Protect More Than the Individual Vaccines work in two ways: by protecting the individual and by protecting the community. When enough people are immune to a disease in a given geographical area or community, germs can’t spread from person to person. They peter out. What’s more, not everyone can be vaccinated due to their age or medical history. Those individuals rely on high vaccination rates to keep them safe from infections. The more people vaccinated, the more everyone (not just those vaccinated) is protected from disease outbreaks. 3 Vaccine-Preventable Diseases Are Dangerous Because vaccines have been so successful, it’s easy to forget just how dangerous vaccine-preventable diseases can be. Even chickenpox — a rite of passage for some generations — is far from harmless. Before a vaccine was available, the virus was responsible for roughly 11,000 hospitalizations and an average of 100+ deaths a year in the United States alone. Without high vaccination rates, diseases that used to cause widespread death and disability could make a comeback. 4 Most People Vaccinate Their Children While “anti-vaccine” advocates get a lot of attention, the truth is the majority of parents trust their health care providers and local health officials and vaccinate their children. In 2017, nine in 10 U.S. toddlers were vaccinated against diseases like measles and polio, and two in three were up to date on all seven of the primary childhood vaccines by their third birthday. Vaccinating is the norm nationwide. 5 “Spacing Out” Vaccines Leaves Kids at Risk Some parents might want to vaccinate their children but worry that giving too many vaccines too early in life can increase the chances of side effects. As a result, they opt to vaccinate according to an adjusted schedule — reducing the number of vaccines given and/or getting them over a longer period of time. At a glance, this might seem like a safe bet, but it carries more risks than parents often realize. The current U.S. recommended vaccination schedule is designed to protect kids as early and as safely as possible. Put together by a panel of medical and public health experts, the schedule takes into consideration the most up-to-date research available on the vaccines and their side effects when given at specific ages or within certain populations (ex. pregnant women), as well as when given with other vaccines at the same time. They look into whether side effects go up when you give specific vaccines together, and they do their best to take that into account when building or tweaking the schedule. It’s a continuous process. The panel meets multiple times a year to discuss any new information, and then it updates the schedule on an annual basis to make sure it is as safe and effective as possible. When parents buck the schedule to pick and choose what vaccines to give their kids and when, they are rolling the dice not just on their child getting infected while they wait to get to the next dose, but also on the safety of their untested alternative schedule. 6 Vaccines Are Tested Extensively For Safety Vaccines are one of the most extensively tested medical products used in the United States today, undergoing more rigorous safety testing that many medications and far more than nutritional supplements. Before a vaccine ever hits pharmacy shelves, they are tested for safety in thousands of individuals and over several years. In order to be approved for use in the United States and elsewhere, vaccine manufacturers first have to prove that side effects are minimal and the benefits are worth any risks posed by the vaccines. Once the vaccines are approved by the Food and Drug Administration or other countries’ governing bodies, researchers continue to study the vaccines to ensure they are safe and effective for as long as they are in use. If at any point the risks of the vaccine start to outweigh the benefits, health officials sound the alarm and the vaccine is pulled. That’s what happened with the polio vaccine. When an oral version of the vaccine was first introduced back in the 1960s, the virus was rampant in the United States. Kids were being paralyzed, and iron lungs were commonplace. The vaccine was made using live (but severely weakened) polio virus, which made it highly effective at eliminating polio all over the world. But that effectiveness carried some risks, as a very small number of people would get a form of polio from the vaccine itself. By the mid-1990s, polio cases had plummeted, and the only cases of polio seen in the country were a direct result of the vaccine. At that point, the risks were greater than the benefits, and the vaccine was replaced with a safer (though slightly less effective) inactivated vaccine. Vaccinated vs. Unvaccinated Studies Large-scale, randomized control studies—where a large intervention (ex. vaccinated) group is directly compared to a large control (ex. unvaccinated) group—are something of a gold standard for science. Health is complicated, and a lot of things can influence outcomes. Being able to control one of those factors helps eliminate some of the uncertainty about what might be contributing to a given outcome (ex. autism). When it comes to vaccines, however, these kinds of studies aren’t always ethical. Randomly and deliberately leaving some individuals—especially children—vulnerable to a disease when there is a safe and effective vaccine available goes against many of the moral and ethical codes guiding modern science. No institutional review board would approve such a study, and it’s extremely unlikely to be published in a reputable journal. That’s why many vaccine-related studies don’t use placebos in their control group. Instead, they use already existing vaccines (the status quo) and account for the different factors using statistical formulas. 7 Vaccines Don’t Contain “Toxins” Taken out of context, some ingredients currently or previously used in developing vaccines can seem a little worrisome — which is why it’s so important to understand first how much of these ingredients are found in vaccines, what effect (if any) they might have on the body in those quantities, and why they’re even added to vaccines in the first place. Toxins vs. Chemicals If you search for “vaccine ingredients,” you might come across websites inaccurately labeling chemicals found in some vaccines as toxins. A chemical is something that’s made up of chemical elements like hydrogen or carbon, whereas a toxin is something that’s poisonous to people. It’s an important distinction because while some chemicals can be harmful, not all chemicals are toxic. In small doses, a chemical is typically harmless. It only becomes a toxin when taken in large enough doses to cause harm. Take, for example, dihydrogen monoxide (more commonly called water). It’s a crucial chemical we ingest every day. The overwhelming majority of the time, it is completely safe—and even beneficial—but in big enough doses, drinking too much water or being around it without taking precautions can be life-threatening. It’s important to keep all this in mind when reading about vaccine ingredients online. Vaccine Ingredients Are Safe While some vaccine ingredients might sound scary, studies show them not only to be safe in the amounts used, but they also make the vaccines more effective and have fewer likely side effects. For example, here are some vaccine ingredients that might seem harmful but are actually very safe when you look at how much is in vaccines, why it’s there, and how the body reacts to it. Mercury: While some vaccines used to be made with a mercury-containing ingredient called thimerosal, the ingredient has been removed from nearly all vaccines except for select flu and tetanus vaccines. More importantly, however, the mercury in thimerosal was ethylmercury—not methylmercury, the toxic substance found in tuna. Ethylmercury is processed much more quickly by the body and is as similar to methylmercury as tequila (ethyl alcohol) is to antifreeze (methyl alcohol).Aluminum: Aluminum salts are sometimes added to vaccines to help make them more effective at boosting immunity. They've been included in vaccines for more than 70 years and have a strong safety track record. Like ethylmercury, aluminum is processed quickly by the body, especially when you consider the very small amount used in vaccines and how much you're already exposed to on a daily basis. There's more aluminum in breast milk and baby formula, for example, than there is in vaccines.Formaldehyde: Formaldehyde is sometimes used in the manufacturing process to deactivate viruses or toxins so that they can be safely used in vaccines. Nearly all of it is removed before the vaccine is packaged, however, and only trace amounts are actually left in the vaccine. What's more, formaldehyde is a naturally occurring substance found in the environment, and the amount found in vaccines is substantially lower than what is already safely circulating in the body. 8 Vaccine "Shedding" Can Happen, But It Rarely Results in Illnesses Some vaccines are made using "live" viruses that have been weakened in the laboratory over time. They look and act a lot like the real thing, prompting the body to develop immunity like it would with a natural infection, but they don't cause sickness like wild viruses do. Because vaccine viruses can mimic a natural infection, they are sometimes detectable in the stool or respiratory droplets (ex. from coughs and sneezes) for a short time after vaccination. This is often referred to as "shedding," and it can cause some people to be exposed to the vaccine virus. For the overwhelming majority of people, coming into contact with a vaccine virus is completely harmless. Remember—vaccine viruses are weakened. They don't cause illness or outbreaks. In extremely rare cases, however, immune-compromised individuals—like transplant patients or those undergoing treatment for cancer—could potentially get sick or experience symptoms (like a rash) from vaccine viruses if they're exposed to them. This almost never happens. That's because not all live vaccines cause shedding, and when they do, it is still a weakened version of the virus. A person typically has to be severely immune-compromised to develop an infection due to vaccine shedding. Even then, a weakened version of the virus is still less of a threat to their health than an infection with the wild virus would be, especially considering their medical conditions might prevent them from being vaccinated themselves. For these individuals, vaccine shedding isn't a reason for their loved ones to forgo vaccines because high vaccination rates in their communities help keep them safe from wild viruses that could be much more dangerous to their health. The only exception is the live oral polio vaccine, which is no longer used in countries like the United States. A person can mitigate the risk vaccine shedding poses to their immune-compromised friends and family by limiting contact with them for the first few weeks after receiving live vaccines like those against rotavirus or chickenpox. 9 Vaccines Don’t Cause Autism The signs and symptoms of autism spectrum disorder (ASD) typically appear around age 18 to 24 months, right around the time kids are receiving their early childhood vaccines, which is why some think the two are connected. However, multiple studies looking at hundreds of thousands of cases show vaccines do not increase a child’s risk of autism, even when the child is at an increased risk of autism already. There are few things that scientists can say with certainty. After all, science is all about questioning assumptions and testing theories. But after roughly two decades of research, it’s abundantly clear that vaccines do not cause autism. The pervasive myth that the two are linked has roots in a 1998 now-retracted article published in the medical journal “The Lancet.” The article examined just 12 children who had intestinal issues, developmental conditions like ASD, and (in most cases) had received the MMR (measles, mumps, and rubella) vaccine. The authors explicitly wrote in the paper that they “did not prove an association between measles, mumps, and rubella vaccine and the syndrome described.” But that didn’t stop the lead author, Andrew Wakefield, from publicly connecting the MMR vaccine with autism and prompting a frenzy of news reports, followed by measles outbreaks for years to come. There were a lot of things wrong with the Wakefield paper that eventually led it to be retracted by the journal. Later investigations would reveal that the kids included in the study were handpicked by the researchers and recommended for the study by lawyers suing vaccine manufacturers. Wakefield himself had financial stakes in the paper’s outcome. And key data points in the paper were distorted or flat-out falsified. Wakefield was stripped of his medical license, and the paper was pulled. But the consequences of the article and its lead author’s erroneous public comments are still apparent today. It’s unclear what does cause ASD, but there are some things that can increase a person’s risk of having it—none of which have to do with vaccination status. These risk factors include:A family history of ASDCertain genetic or chromosomal conditionsUsing specific prescription drugs during pregnancyHaving older parents 10 Vaccines Side Effects Are Almost Always Mild Vaccines don’t cause autism, and they don’t contain toxins or heavy metals that can build up in the body. But they can cause some mild side effects like fever, soreness, or fatigue. No one likes having a sore arm or comforting a baby through a fever, but while unpleasant, these side effects tend to be mild and short-lived, and they are significantly less dangerous than the symptoms of vaccine-preventable diseases like measles or meningococcal meningitis. In extremely rare cases, a vaccine can cause a serious allergic reaction. Just like some people are deathly allergic to peanuts or penicillin, some people can be highly allergic to specific ingredients found in one or more vaccines. This, however, is extraordinarily rare. Out of a million doses of vaccine, only one or two might cause a serious, anaphylactic reaction. These reactions tend to happen within a few minutes or (less commonly) hours after receiving a vaccine and, while serious, can often be managed with prompt treatment. The diseases vaccines prevent are much more dangerous and difficult to manage. Measles, for example, kills about 1-2 out of every 1,000 people who get it—even with good medical care—and can lead to permanent brain damage or fatal complications years after a person has recovered. A Word From Verywell There’s a lot of misinformation out there about vaccines, but the research is overwhelmingly clear: Vaccines are safe, effective, and necessary to protect the health and safety of individuals and communities. Even so, if you have questions or concerns about vaccines or their ingredients, talk to your health care provider. They are the best person to discuss with you the risks and benefits vaccines will have for you and your family. Was this page helpful? Thanks for your feedback! Sign up for our Health Tip of the Day newsletter, and receive daily tips that will help you live your healthiest life. Email Address Sign Up There was an error. Please try again. Thank you, , for signing up. What are your concerns? Other Inaccurate Hard to Understand Submit Article Sources Advisory Committee on Immunization Practices. Evidence-based recommendations: GRADE. Centers for Disease Control and Prevention. Centers for Disease Control and Prevention. Vaccine testing and the approval process. Centers for Disease Control and Prevention. Timing and spacing of immunobiologics. Centers for Disease Control and Prevention. Epidemiology and Prevention of Vaccine-Preventable Diseases. Hamborsky J, Kroger A, Wolfe S, eds. 13th ed. Washington D.C. Public Health Foundation, 2015. Centers for Disease Control and Prevention. Ingredients of vaccines: Fact sheet. Centers for Disease Control and Prevention. Vaccines do not cause autism. Children's Hospital of Philadelphia. Vaccine ingredients: Aluminum. Offit PA, Moser CA. The problem with Dr Bob's alternative vaccine schedule. Pediatrics. 2009;123(1):e164-9.