Immunized vs Vaccinated: What's the Difference?

Understand how shots can build immunity to diseases

The terms immunized, vaccinated, and inoculated are often used interchangeably, but they have different meanings. Vaccination describes the act of receiving a vaccine. Immunization and inoculation describe the process of becoming immune through vaccination.

Those differences may seem minor. Still, using terms correctly can prevent misunderstandings with your healthcare provider.

This article explains the differences, what vaccines do, and why their timing is important.

Vaccination vs. Immunization

Verywell / Mayya Agapova

Vaccination vs. Immunization vs. Inoculation

The World Health Organization (WHO) says vaccination and immunization are related terms. But vaccination describes a specific action, while immunization describes a process.

By the WHO definition:

  • Vaccination: The use of vaccines to stimulate your immune system to protect you against infection or disease
  • Immunization: The process of making you immune or resistant to an infectious disease, typically via vaccination

The Centers for Disease Control and Prevention (CDC) offers similar definitions:

  • Vaccination: The act of introducing a vaccine to give you immunity to a specific disease
  • Immunization: The process by which vaccination protects you from a disease

You can become immunized to a disease by being exposed to the disease-causing organism (pathogen) and developing antibodies to fight it. But in modern usage, immunization almost always means immunity by vaccination, not by natural infection.

The term inoculation is often used as a synonym for vaccination or immunization.

The term was first coined in the 18th century. It described variolation—introducing a small amount of pus from someone with smallpox into the body of someone without it.

Today, though, the term almost always means immunity through vaccination. So it's basically the same as immunization.


Vaccination is the use of vaccines to give you immunity to a disease. Immunization is the process that happens in your body. Usually that's due to vaccination but it can come from other exposure to a pathogen. Inoculation has come to mean the same thing as immunization.

What Vaccines Do

Vaccination and immunization protect you from potentially deadly diseases. Vaccines now prevent diseases that once killed millions. These include polio and influenza (the flu). 

Vaccines put your immune system to work. First, your immune system recognizes an invader as harmful. Then it makes antibodies designed to target that specific disease.

It also creates memory cells. These can re-launch an attack if the pathogen returns. This lowers your risk of getting sick again. The process is called the acquired (or adaptive) immune response.

Everyone is protected when enough people in a community are vaccinated. That includes those who aren't vaccinated. This is due to herd immunity.

Herd immunity means that there aren't enough vulnerable people in a community for an infection to spread widely. When diseases can't spread, they die out.

That's how public health officials have eliminated (or nearly eliminated) diseases like:


Vaccines train your immune system to recognize harmful organisms and fight them. They also remember pathogens so they're ready to fight them again later on. This is called the acquired or adaptive immune response.

Herd immunity is reached when enough people in a community are immune such that a pathogen can't spread widely. It even protects those who aren't vaccinated.

Vaccine Timing and Effectiveness

Starting at birth, babies get a lot of vaccinations. That worries some parents.

But following the recommended schedule is important. Vaccinations are timed to protect against specific diseases when your child is most at risk.

The CDC's vaccine schedule has been proven safe and effective at protecting children from common diseases. Not getting vaccinated places a child at serious risk.

Unvaccinated children have a much higher chance of severe illness and death from:

Some vaccines are also recommended for adults. These vaccines help prevent:

You need some vaccines once and others every so often. That's because the immunity can wear off over time. How long it lasts is called the duration of immunity.

When immunity begins to wane, you might need a booster or another vaccine. Tetanus and COVID-19 are examples of this.


Vaccination gives you immunity to a specific pathogen. Immunization is the process of developing immunity. The word usually refers to immunity through vaccination, but it can occur through infection, as well. Inoculation is a synonym for vaccination and immunization.

Vaccines teach your immune system to recognize and fight specific germs. Herd immunity means too many people are immune for a pathogen to spread. This protects those who aren't vaccinated.

Vaccines are timed to protect you and your children when you're most vulnerable to certain illnesses. It's important to follow the CDC's vaccine schedule.

A Word From Verywell

You may have heard a lot of anti-vaccine fears. They aren't supported by medical research.

Vaccines go through strict testing and the demanding FDA-approval process. They must be proven safe and effective before they're given to patients.

So protect yourself and your family from potentially deadly illnesses. Talk to your healthcare provider to make sure you're up to date on vaccines.

Frequently Asked Questions

  • What are the different kinds of vaccines?

    The many different kinds of vaccines include:

    • Live-attenuated vaccines
    • Inactivated vaccines
    • Subunit, recombinant, polysaccharide, and conjugate vaccines
    • Toxoid vaccines
    • mRNA vaccines
    • Viral vector vaccines

    Depending on the type, the vaccine may use:

    • A weakened version of the disease-causing germ
    • A dead version of the germ
    • Parts of the germ
    • A toxin that harms the germ
    • Genetic material that helps you develop an immune response
  • How does herd immunity work?

    Herd immunity protects communities from disease outbreaks. It's reached when enough people are vaccinated or otherwise immune that the disease can't spread.

    Then, the people who are most vulnerable due to age or illness aren't exposed to the illness.

  • How do vaccines get FDA approval?

    Vaccines get FDA approval by going through a rigorous process. It involves research, development, testing, and approval process.

    • First, research shows the vaccine is necessary.
    • Then the FDA approves testing.
    • Initial testing is done on animals.
    • At least three phases of human testing are done.
    • If it's safe and effective, the vaccine can move on to the FDA's approval process.

    Even after approval, the FDA still closely monitors vaccines for any problems.

  • Is the COVID shot a vaccine or immunization?

    The COVID shot is a vaccine. Receiving a series of COVID shots will immunize you against the COVID virus. 

  • What is an immunization schedule?

    An immunization schedule is a list of recommended vaccines each person should receive according to age. The immunization schedule includes both the vaccines, the number of doses for each, and how far apart each dose should be spaced. In the United States, the U.S. Centers for Disease Control and Prevention creates the recommended schedules, which are approved by medical organizations such as the American Academy of Pediatrics.

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11 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
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  2. Centers for Disease Control and Prevention. Immunization: the basics.

  3. Boylston A. The origins of inoculation. J R Soc Med. 2012 Jul;105(7):309-13. doi:10.1258/jrsm.2012.12k044

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  6. Holzman H, Hengel H, Tenbusch M, Doerr HW. Eradication of measles: remaining challenges. Med Microbiol Immunol. 2016; 205: 201–8. doi:10.1007/s00430-016-0451-4

  7. Centers for Disease Control and Prevention. Multiple vaccines at once.

  8. Centers for Disease Control and Prevention. Who should get diphtheria, tetanus, and whooping cough vaccines?

  9. National Institutes of Health, U.S. National Library of Medicine: MedlinePlus. Vaccines.

  10. U.S. Food & Drug Administration. Vaccine Development – 101.

  11. Centers for Disease Control and Prevention. Who sets the immunization schedule?

Additional Reading

By Kristina Duda, RN
Kristina Duda, BSN, RN, CPN, has been working in healthcare since 2002. She specializes in pediatrics and disease and infection prevention.