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Vaccines are injections (shots), liquids, pills, or nasal sprays that you take to teach the immune system to recognize and defend against harmful germs. The germs could be viruses or bacteria.

Some types of vaccines contain germs that cause disease. But the germs have been killed or weakened enough that they won't make your child sick. Some vaccines only contain a part of a germ. Other types of vaccines include instructions for your cells to make a protein of the germ.

These different vaccine types all spark an immune response, which helps the body fight off the germs. Your child's immune system will also remember the germ and attack it if that germ ever invades again. This protection against a certain disease is called immunity.

Babies are born with immune systems that can fight most germs, but there are some serious diseases they can't handle. That's why they need vaccines to strengthen their immune system.

These diseases once killed or harmed many infants, children, and adults. But now with vaccines, your child can get immunity from these diseases without having to get sick. And for a few vaccines, getting vaccinated can actually give you a better immune response than getting the disease would.

Vaccinating your child also protects others. Normally, germs can travel quickly through a community and make a lot of people sick. If enough people get sick, it can lead to an outbreak. But when enough people are vaccinated against a certain disease, it's harder for that disease to spread to others. The entire community is less likely to get the disease. This is called "community immunity."

Community immunity is especially important for the people who can't get certain vaccines. For example, they may not be able to get a vaccine because they have weakened immune systems. Others may be allergic to certain vaccine ingredients. And newborn babies are too young to get some vaccines. Community immunity can help to protect them all.

Vaccines are safe. They must go through extensive safety testing and evaluation before they are approved in the United States.

Some people worry that childhood vaccines could cause autism spectrum disorder (ASD). But many scientific studies have looked at this and have found no link between vaccines and autism.

No, vaccines do not overload the immune system. Every day, a healthy child's immune system successfully fights off thousands of germs. When your child gets vaccines, they are getting weakened or dead germs. So even if they get several vaccines in one day, they are being exposed to a tiny amount of germs compared to what they encounter every day in their environment.

Your child will get vaccines during well-child visits. They will be given according to the vaccine schedule. This schedule lists which vaccines are recommended for children. It includes who should get the vaccines, how many doses they need, and at what age they should get them. In the United States, the Centers for Disease Control and Prevention (CDC) publishes the vaccine schedule.

Following the vaccine schedule allows your child to get protection from the diseases at exactly the right time. It gives their body the chance to build up immunity before being exposed to these very serious diseases.

The flu (influenza) is a respiratory infection. It is caused by influenza viruses that infect your nose, throat, and lungs. These viruses can spread from person to person.

Most people with the flu get better on their own, without medical care. But for some people, the flu is serious. It can cause complications and sometimes even death. People who are 65 and older, under age 5, pregnant, or have certain health conditions are at higher risk of flu complications.

Getting vaccinated against the flu each year is best way to lower your risk of the flu and its complications.

There are many reasons to get a flu shot each year:

• It may keep you from getting sick with the flu.
• If you do get the flu, it may be less severe. You may also be less likely to have complications or need to be hospitalized with the flu.
• If you have certain chronic health conditions, getting a flu shot may help prevent the flu from making your condition worse. For example, if you have COPD or diabetes, the flu can worsen your condition so much that you might need to be hospitalized. Getting a flu shot can lower this risk.
• Getting the vaccine during pregnancy not only helps protect you from the flu during and after pregnancy. It also helps protect your baby from flu during their first few months of life.
• It has been shown to lower the risk of severe life-threatening flu in children.
• It may also protect the people around you, including those who are at higher risk of complications.

The flu vaccine causes your immune system to make antibodies about two weeks after you get the shot. These antibodies provide protection against infection with the flu viruses that are in the vaccine.

The U.S Centers for Disease Control and Prevention (CDC) recommends annual flu shots for everyone 6 months and older, with a few rare exceptions.

Flu shots are especially important for people who are at high risk of developing serious complications from the flu.

There are different types of flu vaccines. There are injectable vaccines (shots) and nasal spray vaccines. There are also some vaccines especially for people 65 and older. Ask your health care provider which one is right for you.

There are some people who should not get a flu shot:

• Children younger than 6 months of age.
• Have severe, life-threatening allergies to flu vaccine or any ingredient in the vaccine. This might include gelatin, antibiotics, or other ingredients.

Some people need to talk to their provider before they get a flu shot. They include people who:

• Have an allergy to any of the ingredients in the vaccine.
• Have ever had Guillain-Barre syndrome(GBS). Some people with a history of GBS should not get a flu vaccine.

If you are moderately or severely ill, you usually need to wait until you recover before getting a flu shot.

You need to get a flu shot every year because:

• Your immune protection from the vaccine declines over time. You need to get the shot every year to boost that protection.
• Flu viruses are constantly changing, so every year, the flu vaccine is updated. The flu vaccine will include protection against the viruses that will most likely be common during the upcoming flu season.

For most people who need only one dose of the flu vaccine for the season, September and October are usually good times to get it. It's best to be vaccinated by the end of October.

Some children need two doses of the flu vaccine. They should get their first dose as soon as the vaccine is available. They need to get the second dose at least four weeks after the first.

If you are pregnant, talk to your provider about when to get the vaccine. When you should get it can vary, based on how far along you are in your pregnancy.

Flu vaccines have been shown to be safe. But like any medical product, they can cause side effects. If you have any side effects, they are usually mild and go away on their own within a few days. Common side effects include:

• Soreness, redness, and/or swelling from the shot
• Headache
• Fever
• Nausea
• Muscle aches

The flu shot, like other injections, can occasionally cause fainting. In rare cases, some people have a serious allergic reaction.

Centers for Disease Control and Prevention

Mercury is an element that is found in air, water and soil. It has several forms. Metallic mercury is a shiny, silver-white, odorless liquid. If heated, it is a colorless, odorless gas. It also combines with other elements to form powders or crystals. Mercury is in many products. Metallic mercury is used in glass thermometers, silver dental fillings, and button batteries. Mercury salts may be used in skin creams and ointments. It's also used in many industries.

Mercury in the air settles into water. It can pass through the food chain and build up in fish, shellfish, and animals that eat fish. The nervous system is sensitive to all forms of mercury. Exposure to high levels can damage the brain and kidneys. Pregnant women can pass the mercury in their bodies to their babies.

It is important to protect your family from mercury exposure:

• Carefully handle and dispose of products that contain mercury
• Limit your consumption of fish with higher levels of mercury

Agency for Toxic Substances and Disease Registry

Vaccines play an important role in keeping us healthy. They protect us from serious and sometimes deadly diseases. Vaccines are injections (shots), liquids, pills, or nasal sprays that you take to teach your body's immune system to recognize and defend against harmful germs. The germs could be viruses or bacteria.

Some types of vaccines contain germs that cause disease. But the germs have been killed or weakened enough that they won't make you sick. Some vaccines only contain a part of a germ. Other types of vaccines include instructions for your cells to make a protein of the germ.

These different vaccine types all spark an immune response, which helps your body fight off the germs. Your immune system will also remember the germ and attack it if that germ ever invades again. This protection against a certain disease is called immunity.

These diseases can be very serious. Because of this, getting immunity from a vaccine is safer than getting immunity by being sick with the disease. And for a few vaccines, getting vaccinated can actually give you a better immune response than getting the disease would.

As with medicines, any vaccine can cause side effects. Most of the time the side effects are minor, such as a sore arm, fatigue, or mild fever. They usually go away within a few days. These common side effects are often a sign that your body is starting to build immunity against a disease.

Serious side effects from vaccines can happen, but they are very rare. These side effects could include a severe allergic reaction. Other possible side effects are different for each vaccine. Talk with your health care provider if you're concerned about your health after getting vaccinated.

Some people worry that childhood vaccines could cause autism spectrum disorder (ASD). But many scientific studies have looked at this and have found no link between vaccines and ASD.

Every vaccine that is approved in the United States goes through extensive safety testing. It starts with testing and evaluation of the vaccine before it's approved by the Food and Drug Administration (FDA). This process can often take several years.:

• First, the vaccine is tested in labs. Based on those tests, the FDA decides whether to test the vaccine with people.
• Testing with people is done through clinical trials. In these trials, the vaccines are tested on volunteers. Clinical trials usually start with 20 to 100 volunteers, but eventually include thousands of volunteers.
• The clinical trials have three phases. The trials are looking for the answer to important questions such as
  • Is the vaccine safe?
  • What dose (amount) works best?
  • How does the immune system react to it?
  • How effective is it?
• During the process, the FDA works closely with the company who makes the vaccine to evaluate the vaccine's safety and effectiveness. If the vaccine is found to be safe and effective, it will be approved and licensed by the FDA.
• After a vaccine is licensed, experts may consider adding it to the recommended vaccine, or immunization, schedule. This schedule is from the Centers for Disease Control and Prevention (CDC). It lists which vaccines are recommended for different groups of people. They list which age groups should get which vaccines, how many doses they need, and when they should get them.

Testing and monitoring continue after the vaccine is approved:

• The company making the vaccines tests every batch of vaccines for quality and safety. The FDA reviews the results of these tests. It also inspects the factories where the vaccine is made. These checks help make sure the vaccines meet standards for quality and safety.
• The FDA, CDC, and other federal agencies continue to monitor its safety, to watch for possible side effects. They have systems to track any safety issues with the vaccines.

These high safety standards and testing help to make sure that vaccines in the United States are safe. Vaccines help protect against serious, even deadly, diseases. They not only protect you, but also help to keep these diseases from spreading to others.