Vaccines and Your Child's Immune System:
Have specific questions about immunizing your infant? See FAQs about Infant Immunization. As a parent, you may get upset or concerned when you watch your baby get 3 or 4 shots during a doctor's visit. But, all of those shots add up to your baby being protected against 14 infectious diseases. Young babies can get very ill from vaccine-preventable diseases. The vaccination schedule is designed to protect young children before they are likely to be exposed to potentially serious diseases and when they are most vulnerable to serious infections. Although children continue to get several vaccines up to their second birthday, these vaccines do not overload the immune system. Every day, your healthy baby's immune system successfully fights off millions of antigens-the parts of germs that cause the body's immune system to respond. The antigens in vaccines come from weakened or killed germs so they cannot cause serious illness. Vaccines contain only a tiny amount of the antigens that your baby encounters every day, even if your child receives several vaccines in one day. Combination vaccines take two or more vaccines that could be given individually and put them into one shot. Children get the same protection as they do from individual vaccines given separately—but with fewer shots. Learn more about combination vaccines.

Vaccine Side Effects/Risks:
Like any medication, vaccines, can cause side effects. The most common side effects are mild. On the other hand, many vaccine-preventable disease symptoms can be serious, or even deadly. Even though many of these diseases are rare in this country, they still occur around the world and can be brought into the U.S., putting unvaccinated children at risk. The side effects associated with getting vaccines are almost always minor (such as redness and swelling where the shot was given) and go away within a few days. If your child experiences a reaction at the injection site, you can use a cool, wet cloth to reduce redness, soreness, and swelling. Serious side effects following vaccination, such as severe allergic reaction, are very rare and doctors and clinic staff are trained to deal with them. Pay extra attention to your child for a few days after vaccination. If you see something that concerns you, call your child’s doctor. Learn about diseases and the vaccines that prevent them, including the most common side effects associated with each one. Journey of Your Child's Vaccine Learn in words and pictures about the journey of your child’s vaccine. Learn how to soothe your child before, during, and after vaccination with these tips for your child’s vaccine visit. Learn about who should not get vaccinated with certain vaccines. Understand the risks if you decide not to vaccinate your children. Learn about MMR vaccine safety.
Vaccine Ingredients:
Vaccines contain ingredients, called antigens, which cause the body to develop immunity. Vaccines also contain very small amounts of other ingredients--all of which play necessary roles either in making the vaccine, or in ensuring that the vaccine is safe and effective. These types of ingredients are listed below. Type of Ingredient Examples Purpose Preservatives Thimerosal (only in multi-dose vials of flu vaccine)* To prevent contamination Adjuvants Aluminum salts To help stimulate the body’s response to the antigens Stabilizers Sugars, gelatin To keep the vaccine potent during transportation and storage Residual cell culture materials Egg protein To grow enough of the virus or bacteria to make the vaccine Residual inactivating ingredients Formaldehyde To kill viruses or inactivate toxins during the manufacturing process Residual antibiotics Neomycin To prevent contamination by bacteria during the vaccine manufacturing process *Today, the only childhood vaccines used routinely in the United States that contain thimerosal (mercury) are flu vaccines in multi-dose vials. These vials have very tiny amounts of thimerosal as a preservative. This is necessary because each time an individual dose is drawn from a multi-dose vial with a new needle and syringe, there is the potential to contaminate the vial with harmful microbes (toxins). Learn more about thimerosal, mercury, and vaccine safety. There is no evidence that the small amounts of thimerosal in flu vaccines causes any harm, except for minor reactions like redness and swelling at the injection site. Although no evidence suggests that there are safety concerns with thimerosal, vaccine manufacturers have stopped using it as a precautionary measure. Flu vaccines that do not contain thimerosal are available (in single dose vials).
Ensuring Vaccine Safety:
The United States' long-standing vaccine safety system ensures that vaccines are as safe as possible. In fact, currently, the United States has the safest, most effective vaccine supply in its history. Safety monitoring begins with the U.S. Food and Drug Administration (FDA), who ensures the safety, effectiveness, and availability of vaccines for the United States. Before a vaccine is approved by the FDA for use by the public, results of studies on safety and effectiveness of the vaccine are evaluated by highly trained FDA scientists and doctors. FDA also inspects the sites where vaccines are made to make sure they follow strict manufacturing guidelines. Although most common side effects of a vaccine are identified in studies before the vaccine is licensed, rare adverse events may not be detected in these studies. Therefore, the U.S. vaccine safety system continuously monitors for possible side effects after a vaccine is licensed. When millions of people receive a vaccine, less common side effects that were not identified earlier may occur. If a link is found between a possible side effect and a vaccine, public health officials take appropriate action. They will weigh the benefits of the vaccine against its risks to determine if recommendations for using the vaccine should change. Learn more about the U.S. vaccine safety system. The Vaccine Adverse Event Reporting System (VAERS) is a national system used by scientists at FDA and the Centers for Disease Control and P revention (CDC) to collect reports of adverse events (possible side effects) that happen after vaccination.