Vaccines (Immunizations)

What are vaccines?

Given by injection, mouth or nose, vaccines help prevent serious diseases, including measles, whooping cough, polio, chickenpox, shingles and many more. According to Stephanie Chiang, M.D., a board-certified pediatrician with Sutter, “Vaccines are one of medicine’s greatest tools — helping prevent serious disease, save lives and strengthen community health.”

Vaccines have greatly reduced or eliminated life-threatening diseases that used to kill or disable millions of children and adults.

Depending on the vaccine, you may receive it:

• By injection (shot)
• Orally (drops)
• Through a nasal spray

How do vaccines work?

Vaccines trigger your body to defend itself against dangerous bacteria or viruses, most often by introducing a very small, weakened or dead amount of the bacteria or virus. When your immune system is exposed to this version of a germ, it learns to recognize and destroy it in case you are ever exposed to the real germ in the future.

Getting a vaccine typically means you won’t get sick, or you’ll have a milder infection, from that bacteria or virus.

Types of vaccines

Researchers are continually developing and refining vaccine technology. Currently, vaccine types include:

Live virus vaccines. These use a weakened (attenuated) form of the germ that causes a disease. Although it’s not actually “alive,” the infectious agent is very similar to the natural infection, so these vaccines usually give strong, lifelong protection after one or two doses. Examples of live-attenuated vaccines include:

• Measles, mumps and rubella (MMR)
• Chickenpox

Inactivated vaccines. These use a dead version of the germ that causes a disease. Even though the agent is inactive, your immune system still recognizes and attacks it, building immunity. However, because they’re not as strong as live vaccines, inactivated vaccines may require boosters. Examples of inactivated vaccines include:

• Polio vaccine (given as an injection)
• Flu vaccine (given as an injection)
• Hepatitis A
• Rabies

Biosynthetic vaccines. In some cases, scientists are able to create noninfectious substances that closely mimic a bacteria or virus. Often combined with additional, immune-boosting substances (adjuvants), these vaccines trigger a strong immune response but may require boosters for ongoing effectiveness. Biosynthetic vaccines include:

• Hepatitis B
• Hib (Haemophilus influenzae type B)
• HPV (human papillomavirus)
• Meningitis
• Pneumococcal
• Whooping cough (pertussis)

Toxoid vaccines. A few vaccines use a chemically inactivated toxin from a disease-causing germ to build immunity targeted to that toxin. You may need booster shots for ongoing protection. Examples include vaccines for:

• Tetanus
• Diphtheria

Messenger RNA (mRNA) vaccines. This technology, extensively researched and tested for decades, was used to make some of the COVID-19 vaccines. mRNA vaccines don’t contain any live virus, but instead create proteins that trigger your body’s immune response.

Viral vector vaccines. Also studied for decades, viral vector technology uses a modified version of a different virus than the targeted disease’s virus, to train the immune system to attack the target. Viral vector technology is being studied or used in vaccines against:

• Ebola
• HIV (being studied)
• Zika (being studied)

Are vaccines safe?

Research overwhelmingly supports vaccine safety and effectiveness. (Studies consistently debunk the belief that vaccines cause developmental delays, including autism.) Before the Food and Drug Administration (FDA) approves any vaccine, scientists have studied and tested it, typically for years, to verify its effectiveness and safety.

Having mild side effects (headache, low fever, fatigue or redness at the injection site) after you get a vaccine typically means that your immune system is doing its job. A vaccine will not give you the disease it targets. (For example, you will not contract influenza from the flu vaccine.)

Serious side effects from vaccines are extremely rare, and clinical staff know what to do if you show a strong reaction after receiving a vaccine. For most people, including children, the risk of disease is much greater than a vaccine’s possible side effects.

These and many more national centers support immunizations:

• American Academy of Pediatrics
• American Academy of Family Physicians (AAFP)
• American Medical Association
• American Nurses Association (ANA)
• Centers for Disease Control and Prevention (CDC)

What is community immunity?

According to Daniel Brennan, M.D., a board-certified pediatrician with Sutter, “When enough people in a community are protected against a contagious disease, it's hard for it to spread. Maintaining high levels of vaccination will protect the people who receive the vaccine and offer protection for those with weakened immune systems and infants who are too young to receive their first immunizations.”

When should my child or I get specific vaccines?

The American Academy of Pediatrics (PDF) publishes a schedule for childhood vaccines that includes which vaccines are recommended for children along with recommended intervals for each vaccine. The AAP uses an evidence-based approach in making their vaccine schedule.