Vaccine Safety

Are vaccines safe?

Using four different vaccine examples, this section examines what it means when we ask the question “Are vaccines safe?” and explores the detection of rare side effects using a rotavirus vaccine that is no longer used in the United States.

Dosing safety

Why do babies get the same vaccine doses as adults? Why are some vaccines given as single doses and others as multiple doses? Why do we still need vaccines? Find answers to these questions and more.

Fever and vaccines

What is a fever? Why do children get fevers after vaccinations? Should I treat my child’s fever? Find answers to these questions and more.

Immune system and health

Questions related to vaccines and the immune system are answered here, including common concerns such as whether vaccines weaken or overwhelm the immune system, and whether natural infection is better than immunization.

Vaccine ingredients

Many questions about vaccines revolve around the ingredients in the vaccine vial. Learn why certain ingredients are used, the quantities present in vaccines, and the safety of vaccine ingredients.

Vaccines and chronic conditions

Most people agree that vaccines prevent the diseases they are meant to protect against; however, some people wonder whether vaccines are causing other conditions, in exchange for that protection, such as asthma, autism and multiple sclerosis.

Blood-brain barrier & vaccines

Some people concerned about vaccine safety wonder whether vaccines may enter the brain and cause neurological conditions. In order to affect the brain, vaccine components would need to reach the brain. Importantly, our brains are protected by a barrier, called the blood-brain barrier (BBB), which keeps foreign substances from entering the brain.

Antibody-dependent enhancement (ADE) and vaccines

Antibody-dependent enhancement (ADE) occurs when antibodies created during an immune response worsen responses to future encounters with the pathogen. Both diseases and vaccines can occasionally cause ADE; vaccines that led to ADE are no longer in use, but the experiences are described on this page.

Reviewed on December 02, 2020

Materials in this section are updated as new information and vaccines become available. The Vaccine Education Center staff regularly reviews materials for accuracy.

You should not consider the information in this site to be specific, professional medical advice for your personal health or for your family's personal health. You should not use it to replace any relationship with a physician or other qualified healthcare professional. For medical concerns, including decisions about vaccinations, medications and other treatments, you should always consult your physician or, in serious cases, seek immediate assistance from emergency personnel.