How do vaccines work?

Vaccines work by training your immune system to recognize and fight the virus or bacteria when it comes in contact with your body. They help you fight disease without you getting extremely sick. 

Our immune systems are designed to remember. Once exposed to one or more doses of a vaccine, we typically remain protected against a disease for years, decades or even a lifetime. This is what makes vaccines so effective. Rather than treating a disease after it occurs, vaccines prevent us in the first instance from getting sick. World Health Organization

Can I get the disease from the vaccine?

No. Vaccines train your immune system to create antibodies, just as it does when it’s exposed to a disease. However, because vaccines contain only killed or weakened forms of germs like viruses or bacteria, they do not cause the disease or put you at risk of its complications. World Health Organization

Well, what's in a vaccine?

All the ingredients and the vaccine itself are rigorously tested and monitored for safety. The ingredients all have a specific purpose. World Health Organization

• Antigen is a killed or weakened form of the virus or bacteria. It goes to work training our body what to look for and how to fight off the disease.
• Adjuvants help boost our immune response, so vaccines work better. 
• Preservatives ensure a vaccine stays effective.
• Stabilizers protect the vaccine during storage and transportation.

I know kids get vaccinations, but are vaccines harmful to adults?

We know that childhood vaccines save over 4 million lives every year. They also save adults, but there are some cautions. Some people with medical conditions should wait before getting vaccinations, including:

• Those with chronic illnesses or treatments (like chemotherapy) that affect the immune system;
• Those with severe and life-threatening allergies to vaccine ingredients, which are very rare;
• Those with severe illness and a high fever on the day of vaccination.  World Health Organization

Every authorized or approved vaccine goes through safety testing, including:

• Testing and evaluation of the vaccine before it’s licensed by the Food and Drug Administration (FDA) and recommended for use by the Centers for Disease Control and Prevention (CDC)
• Monitoring the vaccine’s safety after it is recommended for infants, children, or adults 

How do we really know vaccines are safe?

All vaccines go through three phases of clinical trials monitored by the Food and Drug Administration. The tests begin with 10 to 100 healthy volunteers to determine if the vaccine is safe, if the vaccine works, if there are any side effects, and what size dose produces the best results before it is expanded to thousands of volunteers. Only when the FDA determines the vaccine is safe and effective and that the benefits outweigh the risks, is a license approved. U.S. Department of Health and Human Services

Still unsure? Check out these resources:

• Immunize.org
• Health and Human Services
• Centers for Disease Control and Prevention COVID-19 Vaccines
• Chat online to an expert from John Hopkins 

What side effects from vaccines are possible?

The most common side effects after vaccination are mild. They include:

• Pain, swelling, or redness where the shot was given
• Fever
• Chills
• Fatigue
• Headache
• Muscle and joint aches
• Fainting

Common side effects are a good sign that your body is beginning to build protection against the disease. But, there is a risk of more series side effects from vaccinations. For every million doses given, one to two people experience a severe allergic reaction, including:

• Difficulty breathing
• Swelling of the face and throat
• A fast heartbeat
• A bad rash all over your body
• Dizziness and weakness

In the case of a severe allergic reaction, call 9-1-1, go to the nearest hospital, or call your physician. Health and Human Services. Report any allergic reactions to the Vaccine Adverse Event Reporting System.