Brainlag PlusHow vaccines give immunity, herd immunity and coverage data, what antibiotics and painkillers do, and how resistant bacteria arise.
How a vaccine works
A vaccine holds a small amount of a dead or inactive pathogen.
Its antigens make lymphocytes produce the matching antibodies, and memory cells remain. If the real pathogen arrives, the right antibodies are made quickly and the person does not become ill.
When a large proportion of people is immune, the pathogen cannot spread: this herd immunity also protects babies and people who cannot be vaccinated.
- 4800 children, 4392 vaccinated, threshold 92%
- 4392 ÷ 4800 × 100 = 91.5%
- 91.5% is below 92%: herd immunity is not reached
The rest of this lesson and its 15 practice questions are in Plus.
Screen 1 of 4, free to read.
- 15 exam-style questions, marked as you go, each with a worked solution
- Anything you get wrong is saved to your flashcards