Click on the commonly asked questions below to get answers about vaccine safety:
Are Vaccines Safe?
Because vaccines are given to people who are not sick, they are held to the highest standards of safety. As a result, they are among the safest things we put into our bodies. The United States currently has the safest, most effective vaccine supply in history. Vaccines must undergo years of testing before they can be licensed. Once they are being used, vaccines are continually monitored for safety and efficacy. When we talk about vaccine safety, we must consider several issues:
- How do we define something as being “safe?”
If we understand “safe” to mean “free from any negative effects,” then vaccines are not 100% safe. All vaccines have possible side effects. Most side effects are mild, such as fever, or tenderness and swelling at the injection site. But some side effects from vaccines can be severe. For example, the pertussis (whooping cough) vaccine is a very rare cause of persistent inconsolable crying, high fever or seizures with fever. Although these reactions do not cause permanent harm to the child, they can be quite frightening for children and their parents. Get more information about the safety of specific vaccines, including the hepatitis B, pertussis, pneumococcal, and rotavirus vaccines.
- Immunizations, like any medication, can cause side effects. However, a decision not to immunize a child also involves risk.
Parents who choose to not immunize their children put their children and those around them at risk of contracting a disease that could be dangerous or deadly. The negative consequences of choosing to not immunize against pertussis (whooping cough) were recently felt strongly by families and children in Japan and England: decisions to not give children the pertussis vaccine led to a tenfold increase in hospitalizations and deaths from pertussis in these two countries.
Now let’s consider measles: one out of 30 children with measles develops pneumonia. For every 1,000 children who get the disease, one or two will die from it. Thanks to vaccines, we have very few cases of measles in the United States today. However, the disease is extremely contagious, and each year dozens of cases are imported from abroad into the U.S., threatening the health of people who have not been vaccinated and those for whom the vaccine was not effective.
- Very few things are “free from any negative effects."
Even everyday activities contain hidden dangers. For example, every year in the United States, 350 people die in bath- or shower-related accidents, 200 die choking on food lodged in their windpipes, and 100 people are struck and killed by lightning. Despite these numbers, few of us consider eating solid food, taking a bath, or walking outside during a thunderstorm as “unsafe” activities. We just figure that the benefits of the activity clearly outweigh the risks.
If vaccines can cause negative side effects, wouldn’t it be “safer” to just avoid vaccines altogether? Unfortunately, choosing to avoid vaccines is not a risk-free choice -- it is a choice to take a different and much more serious risk.
When you consider the risk of vaccines and the risk of diseases, vaccines are the safer choice. Visit the National Network for Immunization Information for more information on vaccine safety.
Does Thimerosal in Vaccines Cause Autism?
Some parents are concerned that thimerosal, a mercury-containing preservative contained in the influenza vaccine, causes autism - a brain development disorder that impairs social interaction and communication. However, during the past few years, a series of biological and epidemiological studies have shown this concern to be unfounded, and it has never been demonstrated that mercury at the level contained in vaccines causes neurological problems.
Thimerosal was originally added to vaccines to protect them from bacterial contamination. While mercury can have toxic effects in large amounts, there is no evidence that the very small amounts of thimerosal found in vaccines has ever caused problems for children. In fact, an infant who is exclusively breastfed will ingest 15 times the quantity of mercury contained in the influenza vaccine.
Today, with the exception of some flu vaccines, none of the vaccines used in the United States to protect children against 14 infectious diseases contain thimerosal. In addition, thimerosal-free flu vaccines are available for those who wish to completely avoid the preservative. Visit The Children’s Hospital of Philadelphia’s Vaccine Education Center for more information on thimerosal and autism.
There a Lot of "Odd" Ingredients in Vaccines? Are They Safe and Why Are They in Vaccines?
There is a lot of buzz about the different ingredients in vaccines. These ingredients when they stand alone can sound scary but they are each important pieces to making vaccines as potent as they are.
For children with a prior history of allergic reactions to any of these substances in vaccines, parents should consult their child’s healthcare provider before vaccination.
- Aluminum - Aluminum is present in several vaccines to improve the immune response. Some parents are concerned that aluminum in vaccines might be harmful. A Children’s Hospital of Philadelphia’s Vaccine Education Center information sheet answers common questions including "Why is aluminum in vaccines?", "How much aluminum is in vaccines?", "What happens to aluminum after it enters the body?", "Does aluminum accumulate in the body?", "Is the amount of aluminum in vaccines safe?", "What is the harm in spacing out vaccines that contain aluminum?" To read the sheet click here.
- Antibiotics which are added to some vaccines to prevent the growth of germs (bacteria) during production and storage of the vaccine.
- Egg protein is found in influenza and yellow fever vaccines, which are prepared using chicken eggs. Ordinarily, persons who are able to eat eggs or egg products safely can receive these vaccines.
- Formaldehyde is used to inactivate bacterial products for toxoid vaccines, (these are vaccines that use an inactive bacterial toxin to produce immunity.) It is also used to kill unwanted viruses and bacteria that might contaminate the vaccine during production.
- Monosodium glutamate (MSG) and 2-phenoxy-ethanol which are used as stabilizers in a few vaccines to help the vaccine remain unchanged when the vaccine is exposed to heat, light, acidity, or humidity.
For more information about the ingredients in vaccines visit the CDC’s site here.
Isn’t it Too Many Shots Too Soon? My baby is so tiny, won’t his immune system get overwhelmed?
Today, young children receive vaccines to protect them against 14 different diseases and some people question whether this is too many vaccines. Parents are also concerned about the amount of vaccine that is administered to children. The reality is that babies are exposed to a huge variety of bacteria and viruses as soon as they leave the womb. An informational sheet from the Children’s Hospital of Philadelphia answers questions including "What are the active components in vaccines?", "Do children encounter more immunological components from vaccines today than they did 30 years ago?", "Can too many vaccines overwhelm an infant's immune system?", "How many vaccines can children effectively handle at one time?", "How do we know that multiple vaccines can be given safely?", "What is the harm of separating, spacing out or withholding vaccines?" Click here to get more information.
These Diseases Are Not Around Any More. Doesn't the Vaccine Risks Outweigh the Harm of Disease?
It is because vaccines have been so effective in stomping out disease, we don’t see the devastating effects of polio or measles. Without continuing to vaccinate against these diseases, we will see a resurgance in these horrible illnesses. The CDC has created a compelling list of statistics that illustrate the Risk of Diseases vs. the Risk of Vaccines. Even one serious adverse event in a million doses of vaccine cannot be justified if there is no benefit from the vaccination. If there were no vaccines, there would be many more cases of disease, and along with the more disease, there would be serious sequelae and more deaths. But looking at risk alone is not enough - you must always look at both risks and benefits. Comparing the risk from disease with the risk from the vaccines can give us an idea of the benefits we get from vaccinating our children.
To read their report click here.
What to Do If Your Child Has a Severe Reaction to a Vaccine?
If you think your child is experiencing a persistent or severe reaction to a vaccine, call your doctor or take your child to the doctor immediately. Write down what happened and the date and time it happened. Ask your doctor, nurse, or local health department to file a Vaccine Adverse Event Report form or fill out a form yourself online.
Vaccine Safety 
