disease-causing agent

A “breakthrough” simply means that a vaccinated person has tested positive for the disease-causing agent, not that they will become ill or transmit the infection to someone else.

This makes mRNA vaccines different from conventional vaccine platforms, which generally use dead or weakened version of the disease-causing agent to train the immune system to recognize and fight it.

Vaccination is fundamentally based on "showing" your immune system the disease-causing agent, so it can form a biological memory and be primed to fight it.

Early vaccines against viruses were based on weakened, killed, or live but harmless versions of the disease-causing agent.

A vaccine works by introducing proteins from the disease-causing agent into the body to trigger the body’s immune response, which includes making antibodies against bacterial proteins.