vaccine

The word “vaccine” means a substance given to the body to trigger immunity against a disease, usually made from a weakened or inactive form of the germ that causes it. In plain terms, something (usually a shot) that trains the body to fight off a specific disease.

“Vaccine” is pronounced vak-SEEN (/vækˈsin/ in IPA).

Here is “vaccine” used in a sentence: “Scientists developed a new vaccine in record time.”

“Vaccine” is a noun.

The word “vaccine” dates back to around 1700 and comes from Latin. From Latin vaccinus, "of a cow," from vacca ("cow"). Edward Jenner coined the related Latin term variolae vaccinae ("cowpox") in the late 1700s, after using cowpox material to protect people against smallpox.

“Vaccine” is a fairly common word in modern English, usually learned at around the B2 level.

“Vaccine” has 2 distinct senses listed in this dictionary. The most common is: a substance given to the body to trigger immunity against a disease, usually made from a weakened or inactive form of the germ that causes it.

A vaccine is the substance itself — typically made from a weakened or inactive form of a germ — while vaccination is the act of giving that substance to a person or animal. So you receive a vaccine during a vaccination.

A vaccine is given before illness to trigger the body's immunity against a disease, whereas an antidote is given after exposure to counteract a poison or toxin. One prevents; the other treats.

Both are standard: you can say a vaccine against measles or a vaccine for measles. "Against" slightly emphasises protection from the disease and is common in formal or medical writing, while "for" is frequent in everyday speech.

In computing, a vaccine is a program that detects and removes viruses or other malware — what most people now call antivirus software. The usage borrows the medical image of protecting a system against infection.