What’s the definition of a vaccine?

Uncertainty and Misinformation Vaccines

Q: I keep hearing people say ‘it’s not a vaccine’ so, what’s the definition of a vaccine? And are the vaccines for COVID vaccines?

TL;DR: A vaccine is a product that is introduced to your body with the intent to create antibodies against a specific disease, giving you the ability to resist infection.

There are several ways to make a product that does this. Vaccines can be made out of the virus or bacteria that causes the disease, a part of it, a by-product of it, or a substitute for it made in a lab. And yes. All the COVID-19 vaccines are… vaccines. Including the mRNA vaccines.

CDC’s plain language definition of a vaccine is: “A product that stimulates a person’s immune system to produce immunity to a specific disease, protecting the person from that disease.” Other words that are also used to refer to vaccines are vaccinations, shots, immunizations, inoculations, and jabs (in the UK). All of these words refer to products–usually injected–that are designed to produce immunity to a specific disease.

While we’re at it, immunity is “protection from an infectious disease. If you are immune to a disease, you can be exposed to it without becoming infected.” Immunity comes in two flavors: innate immunity and adaptive immunity. Your innate immune defenses help protect you in general from all the things that might make you sick (called pathogens). Your skin is part of your innate immune system. It’s a barrier that keeps all sorts of stuff you touch from getting inside your body, from parasites to pasta sauce.

Adaptive immunity is a targeted response to a certain pathogen. It is something the body has to learn through experience with each pathogen. It’s called ‘adaptive’ because your immune system adapts as it learns. Vaccines create adaptive immunity by teaching the immune system what dangerous pathogens look like *without* exposing you to the dangerous pathogen itself. Later, the cells of your adaptive immune system recognize and destroy the pathogen they match to, like a lock and key.

So to answer the question ‘are these really vaccines’ we need to ask: do the COVID-19 vaccines prompt our bodies’ immune systems to create antibodies against the SARS-CoV-2 virus? Does this produce adaptive immunity against COVID-19 and make you resistant to infection? The answer is yes, so the COVID-19 vaccines are in fact vaccines (regardless of the tech used to get there).

And just for fun, here’s a short classic cartoon take on the origins of the first vaccine (and the word ‘vaccine’ as well!). It’s aimed at elementary-aged kids.

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