Live-Attenuated
Uses a live version of the germ that's been weakened until it's too mild to cause real illness in most people, but still real enough for the immune system to study closely and remember.
Examples: measles, chickenpox.
Vaccine Types
Not every vaccine works the same way. Here are the six main categories in use today, and the different mechanical paths each one takes to teach your immune system something new.
The Six Main Categories
Every vaccine on this list reaches the same goal — a trained immune system — through a different mechanism.
Inactivated
Uses a killed version of the germ — unable to grow, spread, or cause infection at all — so the immune system can examine it up close with essentially no risk.
Examples: hepatitis A, rabies.
mRNA
Delivers genetic instructions that tell your own cells how to briefly build a harmless piece of the germ, which the immune system then learns to recognize.
Examples: COVID-19.
Subunit/Conjugate
Skips the whole germ entirely and delivers just one piece of it — a protein or sugar coating — enough for the immune system to learn what to look for.
Examples: hepatitis B, whooping cough.
Toxoid
Targets the toxin a germ produces rather than the germ itself, training the immune system to recognize and neutralize the harmful substance before it can do damage.
Examples: tetanus, diphtheria.
Viral Vector
Uses a different, harmless virus as a delivery vehicle, carrying instructions into cells in a similar spirit to mRNA but through a different mechanical path.
Examples: Ebola, COVID-19.