“Vaccinate” vs. “Inoculate” vs. “Immunize”: What Are The Differences?

With COVID-19 making the headlines every day, people are learning specialized scientific vocabulary like they never have before. Some of us remember our high school science classes and concepts like DNA and RNA, and the exact role they play in the development of new vaccines. For others of us, however, a quick refresher is in order.

We’ve cracked the code on terms like DNA and RNA for you. Take a look at our explanation of these terms here.

As we continue to battle the virus, you have probably heard about people getting—or eagerly waiting to get—vaccinated or inoculated. You may know that these terms involve the immune system, which might lead you to wonder: are they the same thing as being immunized?

If these words have you perplexed, this article is here to provide you with the quick vocab jab you need to get rid of all of that confusion from your system.

First, what is a vaccine?

A vaccine is “any preparation used as a preventive inoculation to confer immunity against a specific disease, usually employing an innocuous form of the disease agent, as killed or weakened bacteria or viruses, to stimulate antibody production.”

A vaccine usually takes the form of a shot that includes a weakened or harmless version of a virus or bacteria. The vaccine serves as a “practice round” that introduces a disease to your immune system. Your white blood cells fight off this weakened form of the disease so when it encounters the real one, they will be able to quickly react and kill it before it can do any harm.

Vaccines have been around for a while (since the 1790s to be precise) and have dramatically helped us fight off some serious diseases. You might have known that early vaccines led to the complete eradication of the disease smallpox, but did you know that cows played a big part in the creation of the first vaccines? Or that the term vaccine comes from the Latin word for cow? It’s true! You can find out more about vaccines on our definition page.

Vaccines are playing the central role in ending the COVID-19 pandemic. As of mid February 2021, there have been over 184 million COVID-19 vaccines administered around the world with more being distributed every day.

Even before the COVID-19 outbreak, though, vaccines have been a common occurrence for most of us. Even newborn babies receive vaccines, such as the rotavirus and polio vaccines. School-age children are recommended to receive yearly injections of common vaccines that include those for chickenpox, mumps, measles, rubella, tetanus, and influenza. Many adults also regularly get flu vaccines during flu season.

What does vaccinate mean?

Vaccinate, then, is “to inoculate” (we’ll get to this one next, we promise) “with the modified virus of any of various other diseases, as a preventive measure.” As you might have guessed, vaccinate simple means to give a vaccine to someone. Vaccinate is a verb that comes from a back formation of the noun vaccination, meaning the act of injecting a vaccine.

The Centers for Disease Control and Prevention (CDC) provides basic information on the procedures that doctors should follow when vaccinating someone. Typically, a vaccine is put into the body through injection with a sterilized needle into a high density muscle, although some are administered orally or through the nose.

Depending on the vaccine, a person may receive multiple shots at once or may need to return at a later time for another dose. In terms of COVID-19, both of the currently authorized vaccines require two doses.

What does inoculate mean?

Inoculate means “to implant (a disease agent or antigen) in a person, animal, or plant to produce a disease for study or to stimulate disease resistance.” More generally, inoculate means to implant a microorganism (such as a bacteria, virus, or amoeba) into an environment. The noun form of inoculate is inoculation.

The word inoculate is first recorded in the early 1400s. It comes from the Latin verb inoculāre, meaning “to graft by budding, implant.”

In medicine, inoculate almost always refers specifically to vaccines because that is usually the only instance a doctor would want to infect a person with a (weakened) microorganism on purpose. In microbiology, however, inoculate is used more generally to mean any situation in which a scientist introduces a microorganism into a new environment with the hopes it will survive and thrive. For example, a scientist might inoculate an algae bacteria into a petri dish with the intention of studying it later after the bacteria reproduces and grows into a larger sample.

What does immunize mean?

Immunize means “to make immune” or “to render harmless or ineffective; neutralize.” Immunize is a verb based on the adjective immune, which is also used in the name of the immune system. If someone is immune to something, they have protection against it and can’t be affected by it. The noun immunity means that someone or something is immune to something.

In medicine, we describe a person as being immune to a disease. This means that the body is able to quickly recognize a disease and produce molecules known as antibodies to fight against it. Antibodies act like bodyguards of your, well, body and kill any disease that would try to harm it.

For a more thorough explanation of how antibodies work to battle disease, check out our profile on them here.

Vaccination is directly related to immunization when it comes to the human body. Some vaccines cause the body to be immune to a disease for a very long time. Others, such as the tetanus vaccine, only lead to a temporary immunity after which the body “forgets” how to make certain antibodies. In this case, doctors recommend getting a booster shot, which is a follow-up shot designed to boost or renew a person’s immunity gained from an earlier vaccine.

How to use vaccinate, inoculate, and immunize

Of the three words, vaccinate is the most narrow because it specifically means to give a vaccine to someone. Inoculate is more general and can mean to implant a virus, as is done in vaccines, or even to implant a toxic or harmful microorganism into something as part of scientific research. Immunize is the most general of the three words and can mean to grant immunity to a wide variety of things, not just diseases.

Let’s give your lexicon a vocab boost by demonstrating the difference in these three words using example sentences.



  • I volunteered to help the nurses vaccinate the kids against the flu.
  • My sister took her cat to the vet to get vaccinated.



  • The laboratory reported high survival rates among the chimps who had been inoculated with the experimental growth hormone.
  • The fungus quickly died after being inoculated with the toxic bacteria.



  • My doctor said I would need three shots before I was immunized to malaria.
  • He went to three different circuses hoping to immunize himself against his fear of clowns.

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Viruses and bacteria differ in how they interfere with the body. Learn more about their differences here.