Immunity, Vaccination, Cholera and Antibiotics
BiologyΒ· 10.1, 15.1Β· 15 min read
1. 1. Types of Immunity (Extended)β β βββExtended onlyβ± 3 min
Immunity
The ability of the body to resist infection by a pathogen, by producing antibodies or antitoxins, or by white blood cells ingesting pathogens.
Immunity is split into two core categories: active and passive. Active immunity develops when your body produces its own antibodies in response to antigen exposure. Passive immunity develops when you receive pre-made antibodies from another organism, rather than making them yourself.
Natural active immunity: Develops after you recover from an infection, e.g. recovering from chickenpox gives long-term immunity
Artificial active immunity: Develops after you receive a vaccine
Natural passive immunity: Antibodies passed from mother to fetus across the placenta, or to a baby in breast milk
Artificial passive immunity: Injection of antibodies from another organism, e.g. tetanus antivenom
A hiker is given an injection of pre-made tetanus antibodies after stepping on a rusty nail. Name the type of immunity provided, and state one disadvantage of this type of immunity.
- 1
First, identify that the hiker is receiving pre-made antibodies, not producing their own: this is passive immunity.
- 2
Next, note the antibodies are delivered via injection, not a natural biological process: this is artificial passive immunity.
- 3
One key disadvantage is that the immunity is only short-term, as no memory cells are produced to replace the antibodies once they break down.
2. 2. How Vaccination Works (Extended)β β βββExtended onlyβ± 4 min
Vaccine
A preparation containing dead or weakened pathogens, or their harmless antigens, given to stimulate active immunity without causing disease.
Vaccination triggers your immune system to produce antibodies against the specific pathogen in the vaccine, just as it would during a natural infection. It also stimulates production of long-lived memory cells that recognise the pathogen if you are exposed to it later in life.
Explain why a child who has received the polio vaccine will not develop polio if exposed to the live polio virus as an adult.
- 1
The polio vaccine contains harmless polio virus antigens, which trigger the childβs white blood cells to produce anti-polio antibodies and memory cells.
- 2
When the adult is later exposed to live polio virus, the memory cells immediately recognise the antigens, and rapidly produce large quantities of antibodies to destroy the virus before it can cause disease.
3. 3. Cholera: Transmission, Toxin and Control (Extended)β β β ββExtended onlyβ± 3 min
Cholera
A disease caused by a bacterium (Vibrio cholerae) which is transmitted in water contaminated with the bacterium, for example when sewage mixes with drinking water.
Symptoms: Severe watery diarrhoea, vomiting, rapid dehydration, which can be fatal if untreated
Transmission: Occurs when drinking water or food is contaminated with sewage containing cholera bacteria
Control measures: Clean chlorinated drinking water, proper sewage treatment, good food hygiene, and oral rehydration therapy for infected patients
Action of the cholera toxin
The cholera bacterium produces a toxin. This toxin causes chloride ions to be secreted into the small intestine. This lowers the water potential in the gut, so water moves out of the cells lining the intestine and into the gut by osmosis. The result is diarrhoea, dehydration, and a loss of ions from the blood.
You should be able to explain this sequence for Extended tier: cholera toxin β chloride ions secreted into the small intestine β water moves into the gut by osmosis β diarrhoea, dehydration and loss of ions from the blood. This is why oral rehydration therapy, which replaces the lost water and ions, is such an important treatment.
Suggest why cholera outbreaks are common after flood events in areas with no formal sewage system.
- 1
Floodwater mixes with raw sewage from open waste pits, contaminating surface water and wells used for drinking.
- 2
Residents who drink the contaminated water ingest cholera bacteria, leading to widespread infection and an outbreak.
4. 4. Antibiotics: Use and Limitations (Core)β β ββββ± 3 min
Antibiotic
A chemical produced by fungi or bacteria that kills or stops the growth of pathogenic bacteria, without damaging human body cells.
Antibiotics are used to treat bacterial infections: they kill bacteria or stop them from growing, without damaging human body cells. They have no effect on viruses, so they cannot be used to treat viral illnesses such as colds and flu. Some bacteria are resistant to antibiotics, which reduces how effective those antibiotics are.
A patient is diagnosed with a sore throat caused by a virus, and their doctor does not prescribe antibiotics. Explain this decision.
- 1
Antibiotics only kill or inhibit bacteria, they have no effect on viruses, so they will not cure the viral sore throat.
- 2
Prescribing unnecessary antibiotics would increase the risk of antibiotic-resistant bacteria developing in the patientβs body, which could cause harder-to-treat infections later.
5. 5. Extended Only: Memory Cells and Long-Term Immunityβ β β β βExtended onlyβ± 3 min
For Extended tier, you must understand the role of memory cells in long-term active immunity. When your body is first exposed to an antigen (through an infection or a vaccination), white blood cells called lymphocytes produce antibodies. This first response is slow, so you may become ill. Some of these lymphocytes become long-lived memory cells that stay in your bloodstream for years, often for life.
If you are exposed to the same antigen again, the memory cells recognise it immediately and quickly produce large numbers of antibodies. Because the antibodies are made so much faster, and in much larger amounts, the pathogen is destroyed before you develop any symptoms. This is why memory cells give long-term immunity.
A person recovers from an infection. Explain why they are unlikely to become ill with the same disease again, even years later.
- 1
During the first infection, lymphocytes produce antibodies against the pathogen, and some of them become long-lived memory cells that remain in the blood.
- 2
If the same pathogen enters the body again, the memory cells recognise it immediately and quickly produce large amounts of antibody, destroying the pathogen before it can multiply enough to cause symptoms.
6. Common Pitfalls
Wrong move:
Stating antibiotics work on viral infections like colds or flu
Why:
Antibiotics act only on bacteria; viruses are a different type of pathogen and are not affected by antibiotics
Correct move:
Always specify antibiotics are only effective against bacterial diseases, not viral infections
Wrong move:
Claiming passive immunity is long-lasting
Why:
Passive immunity uses pre-made antibodies that break down over time, and no memory cells are produced to replace them
Correct move:
Only active immunity (natural or via vaccination) provides long-term protection, as it produces memory cells
Wrong move:
Stating vaccines contain live, disease-causing pathogens
Why:
Vaccines use dead, weakened, or fragmented pathogens/antigens that cannot cause disease in healthy people
Correct move:
Specify vaccine components are harmless and only trigger an immune response without illness
Wrong move:
Linking cholera transmission to air or casual contact with infected people
Why:
Cholera is exclusively water/food-borne, transmitted via ingestion of contaminated water or food
Correct move:
Always link cholera transmission to contaminated food/water supplies, and control to clean water and sewage treatment
Wrong move:
Omitting reference to memory cells when explaining long-term vaccine immunity (Extended only)
Why:
Extended tier requires explicit mention of memory cells as the mechanism for long-term protection
Correct move:
Include memory cell production as the core reason vaccines provide long-lasting active immunity in Extended answers
7. Quick Reference Cheatsheet
Concept | Core Definition | Extended Add-on |
|---|---|---|
Immunity | Resistance to infection via antibody production or white blood cell action | Active immunity relies on memory cells for long-term protection |
Vaccine | Harmless pathogen/antigen preparation that triggers artificial active immunity | Memory cells remain in the blood; if the pathogen is met again they produce antibodies quickly and in large amounts, giving long-term immunity |
Cholera | Bacterial disease transmitted in water contaminated with the bacterium; causes severe diarrhoea and dehydration | Toxin causes chloride ions to be secreted into the small intestine; water moves into the gut by osmosis, causing diarrhoea, dehydration and loss of ions from the blood |
Antibiotic | Kills/inhibits bacteria, no effect on viruses; some bacteria are resistant | Using antibiotics only when essential limits the development of resistant bacteria such as MRSA |
8. Frequently Asked
Do antibiotics work on viral infections like cold or flu?
No. Antibiotics kill bacteria, so they are only used to treat bacterial infections. They have no effect on viruses, so they cannot treat viral illnesses such as colds and flu. Prescribing antibiotics for viral infections increases the risk of antibiotic-resistant bacteria developing.
Why is passive immunity only short-term?
Passive immunity uses pre-made antibodies from another organism, rather than stimulating your body to produce its own antibodies and memory cells. The foreign antibodies break down over time and are not replaced, so protection only lasts a few weeks or months.
Going deeper
- revision_packCIE 0610 Unit 8 Core + Extended Revision PackCovers all Unit 8 syllabus outcomes with summary notes
What's Next
Now you have mastered immunity, vaccination, cholera and antibiotics for CIE IGCSE Biology 0610, you are ready to move on to the next unit. Remember that in the 2023-2028 syllabus, drugs (Topic 15) is limited to antibiotics only. Practice structured exam questions for this topic to familiarise yourself with Core and Extended marking criteria, paying close attention to command terms like 'explain' which require detailed, sequential answers. Make sure you can distinguish between Core and Extended content: on this page the antibiotics content is Core, while immunity, vaccination and cholera are Extended (Supplement) only.