Vaccine Safety Facts for Parents

As a parent, you want to make the best decisions to protect your child—staying informed helps. Your questions are important and you deserve reliable information to support your decisions. If you want to learn more, ask your doctor for a “consultation visit,” or check out our resources.

Are Vaccine Safe?
Yes. Vaccines are safe. In fact, experts including American Academy of Pediatrics, the Institute of Medicine, and the World Health Organization agree that vaccines are even safer than vitamins. Millions of children and adults are vaccinated every year—safely. Thousands of people take part in clinical trials to test a vaccine before it is licensed by the Food and Drug Administration (FDA). After it’s licensed, the Vaccine Adverse Events Reporting System (VAERS) helps track any health effect that happens hours, days, weeks, or even months later. Anyone can report a possible side-effect so that it can be studied. This monitoring helps ensure vaccines are safe. To learn more about vaccine safety from the Centers for Disease Control and Prevention, visit the CDC vaccine safety page.

What kind of side effects should I know about?
Any medicine can cause reactions in some people. The most common side effects from vaccines are swelling or tenderness at the injection site and fever. Serious allergic reactions are very rare, happening in about 1 person out of a million shots given. If you are concerned about possible side effects, ask questions about what to expect. If you notice an unusual reaction hours or days after your child's immunizations, call the doctor's office for advice.

Why do children today get so many immunizations?
Thirty years ago, vaccines protected young children from only seven diseases. Today, we can protect them from at least 14 dangerous diseases because of medical advances. Many shots are also "boosters" of the same vaccine to give children the best protection possible.

Are diseases of the “old days” really still around?
Yes. Pertussis (whooping cough) is still common in the U.S. Other diseases, such as measles and polio, are circulating in other parts of the world. It just takes one unimmunized traveler to bring a disease home from another country. If immunization levels drop, the rare cases we have in the U.S. could very quickly multiply—putting our children in danger.

  • Measles, for instance, is still common in Europe, Africa, and Asia and continues to show up in California. The disease can cause hospitalizations and death. California is currently experiencing a large outbreak of measles. The outbreak started in December 2014 when at least 40 people who visited or worked at Disneyland theme park in Orange County contracted measles; the disease has now spread to at least half a dozen other states and other countries. Over 100 people have already been infected with measles in California during this most recent outbreak.
  • In 2014, over 11,000 people in California became ill with whooping cough, and three infants died. In 2010, almost 10,000 people in California contracted whooping cough, and 10 infants died.
  • Before chickenpox vaccine was developed, about 4 million would get the disease each year; the disease also put about 10,600 Americans in the hospital and caused more than 100 deaths each year. Children who get chickenpox can get serious skin infections or pneumonia.
What about holistic medicine?
Holistic medicines may be helpful for some conditions, but only vaccines provide specific immunity to diseases. Only vaccines have been scientifically proven to protect against whooping cough, measles, mumps, and other diseases. Breastfeeding is very healthy for your baby, but breastfeeding alone cannot fully protect babies from diseases like whooping cough or measles. Also, antibodies passed on from moms to babies during pregnancy do not last beyond infancy.

What about "natural immunity"?
Some people think getting a disease is the "natural" way to trigger the body's immune response, but this comes at a risk—many vaccine-preventable diseases can have dangerous complications, like pneumonia, blindness, brain damage, and even death.

Vaccines safely trigger a natural immune response—but not the disease. Most vaccines are over 99% effective in preventing illness.

Is it safe for a child’s immune system to have multiple shots?
Yes. Children are exposed to hundreds of viruses and bacteria during normal activities like eating and playing. Getting vaccines is no extra burden—even for babies. Getting combination vaccines, like MMR (that protects against measles, mumps, and rubella), or getting multiple shots during one visit is very safe. Today's vaccines are more refined, so even though kids receive more vaccines, they receive far fewer pieces of germs overall (compared to their parents or grandparents).

What about kids with allergies or other health conditions?
Vaccines are safe for kids with most kinds of allergies. Getting shots may be especially important for children with certain health problems who can get very sick if they catch a disease. If your child has an allergy or any health condition, talk with your doctor. The doctor can tell you if any vaccine should be postponed or avoided.

What about autism?
While some parents first notice signs of autism at about the same time their child gets vaccinated, the two events are not related. Dozens of scientific studies have concluded that there is no link between vaccines and autism. The following organizations have issued statements saying that there is no connection between vaccines and autism: Autism Science Foundation, American Academy of Pediatrics, Institute of Medicine, Mayo Clinic, National Institutes of Health, and World Health Organization.

Autism has been diagnosed more often around the world for many years, yet autism rates are the same in vaccinated and unvaccinated children. Recent studies on autism suggest that children with autism have too many cells in a key area of the brain needed for communication, social and emotional development. This type of brain development occurs during the second trimester of pregnancy—long before a child gets any vaccinations.

In 1998, one study used falsified data to suggest a connection between the MMR vaccine and autism. After further investigation, the journal retraced the study, and the lead author lost his medical license.

Are vaccines harmful because of their ingredients?
No. Although some vaccine ingredients sound like foreign substances, they are familiar to your body. Here are the facts:
  • Aluminum is used in very small amounts to boost the body's immune response, making the shots more effective. Aluminum also occurs naturally in soil, water, and air. During the first 6 months of life, your baby gets more aluminum from breast milk or formula (10 to 140 milligrams) than from all shots combined! Aluminum does not build up, and most leaves the body within a couple of weeks.
  • Formaldehyde is sometimes used to keep vaccines germ-free, but it's also produced naturally in the human body as a normal bodily function to produce energy. In fact, studies show that newborns weighing six to eight pounds already have 50-70 times more formaldehyde in their bodies naturally than they would receive from a single dose of vaccine.
  • Thimerosal is a mercury-containing preservative that is no longer used in routine vaccines, except some forms of flu vaccine. Though no harm is known to have been caused by thimerosal in vaccines, as a precaution California law prohibits giving thimerosal-containing vaccines to pregnant women and children under age 3. Thimerosal-free flu vaccines are widely available.

What about getting shots later, or more spread out?
Skipping or delaying shots leaves your child at risk of catching serious diseases at younger ages—when these diseases are most dangerous. That's why most doctors follow the CDC's recommended immunization schedule, which is based on independent medical science review and updated each year.

Advice to spread out shots is not based on science. Spreading out shot visits may make you feel more comfortable, but it's no help to your child. Research shows that getting several shots at the same visit is safe. Spreading out shots may actually be more stressful for your child.