Vaccine Education

Vaccines can help prevent several diseases, some quite serious. Your doctor can help you figure out if you're up-to-date on your vaccinations.

What is a vaccine?

A vaccine, or immunization, is a preparation made from microorganisms, or germs, given to a person to strengthen his or her immune system. Some vaccines contain inactivated forms of these germs, some contain weakened germs and some contain refined components of the germs. Because of the way they are designed, vaccines won't make you sick. Instead, they will help protect you from illnesses that can lead to serious complications or even death.

Some vaccines are given by injection, while others may be given in pills or a nasal spray. To make the process of vaccination easier and less painful, some vaccines are combined and given at one time.

How do vaccines work?

When you get an infection, your body reacts by producing substances called antibodies. These antibodies attack bacteria and viruses in order to help you get over the illness. Often, antibodies stay in your system and may protect you from getting the same disease again. In addition, when you get sick, your immune system often remembers the infection. The next time you encounter the same bacteria or virus, it can mount an immune response much more quickly.

Vaccines work by mimicking a natural infection without the risk of the infection itself. They encourage the body to produce antibodies and create long-lasting memory. This makes your body better prepared to fight off the real disease when you encounter it.

What diseases can vaccines protect a person from?

According to the Centers for Disease Control and Prevention (CDC), vaccines can help protect people from more than 20 different diseases, including measles, mumps, polio, hepatitis B and the flu. Some vaccines are recommended primarily for people at high risk because of certain circumstances. For example, if you're traveling abroad, you may need specific vaccines based on factors such as your health history and the places you plan to visit. Other vaccines are recommended for everyone, beginning in childhood.

When should I start vaccinating my child?

Doctors recommend immunizing children beginning at birth or within the first two months of life. Many childhood immunizations are completed by age 2, but some are given when children get older. Making sure a child is vaccinated early is important because young children don't have fully developed immune systems and may have a hard time fighting infections. You can view the childhood vaccines recommended by CDC at

Do adults need vaccines?

While the prevention of childhood infections is what most people think about when immunizations are discussed, adults should receive certain vaccines too.

Common adult immunizations include the influenza (flu) vaccine, pneumococcal vaccine, pertussis vaccine, shingles vaccine and human papillomavirus (HPV) vaccine. Other vaccines may also be recommended. The best way to know if you have received the vaccines you need is to ask your doctor.

Is there anyone who shouldn't get vaccines?

According to the American Academy of Pediatrics (AAP)and CDC, you may need to avoid a vaccine if you've had side effects from a vaccine in the past or if you have health problems such as certain cancers or immune system disorders.

Pregnant women and people with certain allergies may also need to talk to their doctor before getting some vaccines. For example, people who have had a severe allergic reaction to eggs need to take special measures for vaccines that are typically grown in eggs, such as the flu vaccine. Talk to your doctor if you have any questions or concerns about your allergies.

Will getting one vaccine protect me forever?

Sometimes several doses of a vaccine may be needed for a person to develop a full immune response.

Other times your ability to fight a disease after receiving a vaccine may lessen over time. With tetanus and diphtheria, for example, booster doses are currently recommended every 10 years to maintain an adequate level of protection.

Additionally, people who get influenza vaccines should get them every year because strains of the disease can change. The vaccine is reformulated each year in anticipation of the strains that are most likely to be in circulation. The vaccine you receive one year may not protect you from the disease that is circulating the next year.

How well do vaccines work?

Most childhood vaccines are 90% to 99% effective in preventing disease, according to the AAP. Other vaccines, such as the flu vaccine, may be less effective, but they will still keep many people from getting sick.

Thanks to immunizations, many highly contagious diseases that were once common in childhood are now relatively rare in the United States, according to CDC. For example, since vaccines have become available, cases of measles, mumps, polio and whooping cough have dropped significantly.

If many of the diseases vaccines protect against are disappearing, doesn't that mean there's no need to be vaccinated for those diseases today?

If many of the diseases vaccines protect against are disappearing, doesn't that mean there's no need to be vaccinated for those diseases today?

Many diseases don't occur or spread as much as they used to. Vaccines, improved nutrition, better living conditions and antibiotics get part of the credit. But the bacteria and viruses responsible for many of these diseases still exist. Measles, for example, although uncommon in the United States, still causes about 140,000 deaths each year worldwide, CDC reports. The majority of cases of measles in the United States in the past few years have come from people traveling in other countries where the disease isn't well-controlled. People need to be immunized to make sure they're protected.

Are vaccines safe?

While no vaccine is 100% safe, overall, vaccines have an excellent safety record, according to CDC. And ongoing medical research and monitoring is making them safer and more effective.

Every vaccine goes through a lengthy approval process. Even after vaccines are licensed, they are carefully monitored.

Some people claim there is a link between vaccines and illnesses such as sudden infant death syndrome (SIDS), diabetes or autism. But no scientific evidence supports these claims, according to CDC.

While some vaccines have been found to cause rare, serious side effects (for example, the oral polio vaccine, which caused one case of paralysis for every 2.4 million doses and is no longer used in the United States), most side effects are mild to moderate and temporary.

Can vaccines cause side effects?

While every effort is made to ensure vaccine safety, vaccines can sometimes cause side effects. Usually, they are mild. A vaccine given by injection, for example, may be slightly painful and can cause swelling at the injection site, according to the AAP.

Symptoms of a more severe reaction can include:

  • A very high fever.
  • A generalized rash.
  • A large amount of swelling.

People with these reactions or other symptoms that concern them should contact their doctor right away.

What if I still have concerns about receiving a vaccine?

The best thing to do is talk to your doctor or refer to a reputable information source such as CDC, the AAP or the U.S. Food and Drug Administration. Don't avoid getting a vaccine without getting the facts. It could be a costly mistake.

Where can I go to learn more?

To learn more about vaccines, visit the Vaccines health topic center in our Health Library. You can also find out more about vaccines at the following websites: