Types of immunity and vaccination
Introduced| English | Meaning |
|---|---|
| vaccine/vækˈsiːn/ | A preparation that trains the immune system to recognise an antigen and develop protective immune memory. |
| active immunity/ˈæktɪv ɪˈmjuːnɪti/ | Protection arising when a person's own immune system responds to an antigen and develops immune memory. |
| memory cell/ˈmeməri sel/ | A long-lived immune cell that enables a faster or stronger response when the same antigen is encountered again. |
| passive immunity/ˈpæsɪv ɪˈmjuːnɪti/ | Protection provided by antibodies received from another source, rather than produced by the recipient's own immune response. |
| herd immunity/hɜːd ɪˈmjuːnɪti/ | Protection of a whole population when enough people are immune that the pathogen cannot spread. |
Training the body's defences
- Immunity can be active or passive, and natural or artificial.
- A vaccine 疫苗 gives you immunity without the illness.
- Vaccinate enough people and you protect the whole community.
A vaccine gives a person which kind of immunity?
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A vaccine makes the body respond itself, so it builds active, long-lasting immunity.
Active vs passive
- Active immunity 主动免疫: your own body meets an antigen and makes its own antibodies and memory cells 记忆细胞. Slow to start, but long-lasting.
- Passive immunity 被动免疫: ready-made antibodies are given from outside. Works at once, but does not last (no memory cells).
The four kinds of immunity
Passive immunity (ready-made antibodies) acts fast but is short-lived, because no memory cells are made.
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Passive immunity gives instant antibodies but no memory cells, so it wears off; active immunity is slower but lasts.
Natural vs artificial
| Natural | Artificial | |
|---|---|---|
| active | after an infection | a vaccine |
| passive | antibodies from mother to baby | injection of ready-made antibodies |
Match each type of immunity to its example.
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Active = your own response (infection / vaccine); passive = ready-made antibodies (mother-to-baby / injection).
Vaccination and herd immunity 群体免疫
- A vaccine contains antigens (a dead/weakened pathogen, or part of one).
- They trigger a primary response and make memory cells — long-term immunity without illness.
- If enough people are vaccinated, the pathogen cannot spread easily — protecting even the unvaccinated. This is herd immunity.
When most of a population is vaccinated, the pathogen can't spread, protecting the few who aren't
How a vaccine works
Step through it. A vaccine triggers a primary response and memory cells, so the real pathogen meets a fast, strong defence.
A vaccine gives immunity without illness because it:
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The antigens in a vaccine cause a primary response and memory cells — immunity, but without the disease.
Put how a vaccine protects you in order.
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The vaccine trains the immune system in advance, so the real infection is destroyed quickly.
Herd immunity protects unvaccinated people because:
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With enough of the population immune, the pathogen has too few hosts to spread, protecting everyone.
When enough of a population is vaccinated that the pathogen cannot spread, the unvaccinated are protected by ______ immunity.
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Herd immunity protects those who cannot be vaccinated (e.g. babies, the ill) by stopping the pathogen spreading.
You've got it
- active = your own antibodies + memory cells (slow, lasting); passive = ready-made antibodies (fast, short)
- natural (infection / mother-to-baby) vs artificial (vaccine / injection)
- a vaccine = antigens → memory cells → immunity without illness
- herd immunity: enough vaccinated → pathogen can't spread → protects everyone