Common Questions About Vaccines
Find evidence-based answers to commonly asked questions.
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Overview
We all want to live long healthy lives. Having questions about your health and vaccines is a way of being invested in your personal healthcare. When seeking answers to questions about our health, it can be difficult to wade through the immense amount of information out there. Our community of expert immunologists are here to provide you with information you can trust. To learn more about your personal health, talk to a doctor or visit a local health clinic.
Key Points
- Having questions about vaccines means you are invested in your health. Be sure to seek out credible, accurate information from healthcare providers.
- For the most personalized information, speak to a doctor or visit a local health clinic
Why are Vaccines Needed for Diseases that are No Longer Around?
Vaccines are one of the most successful medical interventions invented. In the last 50 years, over 150 million lives worldwide have been saved thanks to vaccines. In the US over the last 30 years, immunization efforts have prevented an estimated 508 million cases of illness, 32 million hospitalizations, and over one million deaths. This immense success is why we don’t see cases of disease, like polio, that used to be common childhood infections.
However, just because we no longer see cases of the disease, does not mean the pathogens that cause these diseases have disappeared. The pathogens are still around us in the environment. Because vaccines give the immune system a head start against viruses, bacteria, and other pathogens that cause infectious diseases, the immune system stops them before they make us sick. The fact that it seems like diseases like polio or diphtheria are no longer around, is evidence that our vaccines are doing their job and protecting us.
Do Vaccines Cause Autism?
The idea that the childhood vaccine against measles, mumps, and rubella (MMR) causes autism is based on a discredited study that inaccurately linked the MMR vaccine to autism in a small group of children. When it was discovered that the lead scientist lied and falsified the data, the findings from this study were removed. Many rigorous studies by other groups found no link between the MMR vaccine and autism. Similarly, the small amounts of thimerosal, a vaccine preservative present in a small number of vaccines, has also been shown to have no relationship to autism. Rates of autism have continued to rise even though thimerosal ceased to be used as a preservative in routine childhood vaccines decades ago.
In fact, a very recent study from July 2025 tracked health outcomes for 1,224,176 children in Denmark for whether their frequency of vaccine exposure might be associated with 50 different health conditions, including autism spectrum disorder. The researchers concluded that “they did not find evidence supporting an increased risk for autoimmune, atopic or allergic, or neurodevelopmental disorders associated with early childhood exposure to aluminum-adsorbed vaccines”. There was actually a small but significant decrease in the incidence of neurodevelopmental disorders in vaccinated children compared to unvaccinated kids.
Why are Vaccines Required to Attend School?
Vaccines are one of the most effective ways to keep children, and the entire school community, safe from serious diseases like measles, whooping cough, and chickenpox. When children are vaccinated, it helps protect those who can’t be, such as kids with certain medical conditions or those too young to receive the vaccine. Schools are places where illnesses can spread quickly, so vaccine requirements help prevent outbreaks and keep classrooms healthy and open. They also help to prevent kids from bringing germs home from school and exposing their families. Individual vaccination and community immunity keep communities safe from infectious disease. School requirements aren’t just about individual protection; they’re about making sure all children can learn and grow in a safe environment while keeping the whole community healthy.
Is vaccine-acquired immunity better than infection-induced immunity?
Both infection-induced immunity and vaccine-induced immunity provide protection to pathogens. The main difference is that they are making antibodies and learning to provide protection in response to different triggers that activate the immune system. Infection-induced immunity is developed after your body encounters a pathogen and must fight it off.
Vaccine induced immunity is developed in response to a harmless form of a pathogen, a part of a pathogen, or the instructions to make a portion of a pathogen. This vaccine exposure trains the immune system to fight the pathogen if it encounters it later.
In fact, in many cases the vaccine-induced immunity is superior to infection-induced immunity, because it comes without the risks of disease. A measles infection can wipe out your immunity to past pathogen and vaccine exposures. Other serious complications from vaccine-preventable diseases could be brain swelling from chickenpox, birth defects from rubella, cancer from viruses like HPV or Hepatitis B, or death. Vaccines train the immune system without the risk of these dangerous side-effects, making them a safer way to gain immunity than infection-induced immunity.
Are the Ingredients in Vaccines Safe?
The ingredients in vaccines are carefully tested to ensure safety. Every component, whether it’s a small amount of a preservative or an ingredient that helps the vaccine work better, has a specific purpose and is used in small, safe amounts. Vaccine ingredients have been studied for decades and are monitored continuously by health experts and agencies like the CDC and FDA.
For example, aluminum salts are used in vaccines to help the immune system respond better. Aluminum is very common in the environment around us, including in soil and the air. Both adults and children encounter more aluminum in the environment around them than they ever do from vaccines. Vaccines (and the ingredients in them) are designed to protect you and/or your child without causing harm. Their safety is backed by years of research and real-world use.
Sources
Global immunization efforts have saved at least 154 million lives over the past 50 years, World Health Organization
Health and Economic Benefits of Routine Childhood Immunizations in the Era of the Vaccines for Children Program — United States, 1994–2023, Morbidity and Mortality Weekly Report
Aluminum-Adsorbed Vaccines and Chronic Diseases in Childhood: A Nationwide Cohort Study, Annal of Internal Medicine
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