IB MYP 4-5 Biology-Vaccination- Study Notes - New Syllabus
IB MYP 4-5 Biology-Vaccination- Study Notes – New syllabus
IB MYP 4-5 Biology-Vaccination- Study Notes – IB MYP 4-5 Biology – per latest IB MYP Biology Syllabus.
Key Concepts:
- Immunity: Active (vaccines) vs. passive (maternal antibodies).
- Vaccine Types: Live-attenuated (MMR), mRNA (COVID-19).
- Herd Immunity: Thresholds and ethical dilemmas.
- Antibiotic Resistance: Misuse and consequences.
Immunity (Active vs. Passive – Vaccines & Maternal Antibodies)
🧠 What is Immunity?
Immunity is the ability of the body to defend itself from pathogens (like bacteria, viruses, parasites) and prevent disease.
There are two main types of immunity:
- Active immunity
- Passive immunity
💪 1. Active Immunity
🧬 Definition: Your own immune system produces antibodies after being exposed to an antigen.
📌 This can happen in two ways:
- Natural active immunity → after infection (e.g., getting chickenpox)
- Artificial active immunity → after vaccination (e.g., MMR shot)
🔁 Key Features:
- Long-lasting (sometimes lifelong)
- Memory cells are formed
- Slower to act at first exposure, but faster next time
💉 Vaccines (Artificial Active Immunity):
- Contain weakened, dead, or inactivated pathogens
- Trigger immune response → produces antibodies + memory cells
- Examples: Polio, COVID-19, Tetanus
🍼 2. Passive Immunity
🧬 Definition: Ready-made antibodies are given to the body, not made by it.
📌 This can happen in two ways:
- Natural passive immunity → from mother to baby
- Antibodies pass through placenta (before birth)
- Or via breast milk (after birth)
- Artificial passive immunity → injection of antibodies (e.g., after snake bite or rabies exposure)
🔁 Key Features:
- Immediate protection
- Short-lived (no memory cells made)
- Useful in emergencies or when the body can’t make its own response fast enough
🧪 Active vs. Passive Immunity (Comparison Table)
| Feature | Active Immunity 💉 | Passive Immunity 🍼 |
|---|---|---|
| Antibodies made by | Your own body | Another organism |
| Time to develop | Slower | Immediate |
| Memory cells? | Yes 🧠 | No ❌ |
| Lasting protection? | Long-term | Short-term |
| Examples | Vaccines, infection | Breast milk, antibody injections |
✨ Did you know? A baby’s natural passive immunity fades after a few months – that’s why vaccines are scheduled early in life.
💉 Some vaccines need boosters to remind the immune system!
✅ Summary Points
- Active immunity = long-term, body makes its own antibodies
- Passive immunity = short-term, antibodies come from outside
- Vaccines = best example of artificial active immunity
- Maternal antibodies = classic case of natural passive immunity
Vaccine Types (Live-Attenuated – MMR, mRNA – COVID-19)
🧠 What Are Vaccines?
A vaccine is a biological preparation that trains your immune system to recognize and fight pathogens – without actually causing the disease.
Vaccines expose the body to safe versions or parts of the microbe, triggering active immunity (i.e., your body makes memory cells and antibodies).
🧪 Types of Vaccines (With Examples)
✅ 1. Live-Attenuated Vaccines
🧬 What is it? Vaccines made from living pathogens that have been weakened (attenuated) so they can’t cause disease in healthy people.
🦠 These organisms can still replicate inside the body → strong immune response!
MMR Vaccine (Measles, Mumps, Rubella)
🔍 Key Features of Live-Attenuated Vaccines:
| Feature | Description |
|---|---|
| Contains live microbe? | Yes, but weakened |
| Immune response | Strong & long-lasting |
| Doses needed | Usually 1–2 doses |
| Memory cells formed? | Yes ✅ |
| Risk | Not suitable for immunocompromised people |
| Storage | Often needs cold storage |
🧬 2. mRNA Vaccines
💡 What is it? This is a newer type of vaccine (used in COVID-19). Instead of using the virus itself, it contains messenger RNA (mRNA) that gives your cells instructions to make a harmless piece of the virus – usually a protein.
Your immune system then learns to recognize and destroy that protein if the real virus shows up later.
Pfizer-BioNTech and Moderna COVID-19 Vaccines
🔍 Key Features of mRNA Vaccines:
| Feature | Description |
|---|---|
| Contains live virus? | No — just genetic code |
| Risk of infection? | Zero — virus isn’t present |
| Immune response | Strong, especially with 2 doses |
| Memory cells formed? | Yes ✅ |
| Technology | First wide-use of mRNA tech |
| Storage | Requires ultra-cold storage ❄️ |
| Safety | Very safe, even for immunocompromised patients |
🧪 Live vs. mRNA Vaccine – Comparison Table
| Feature | Live-Attenuated 💉 | mRNA 🧬 |
|---|---|---|
| Contains actual virus? | Yes, weakened form | No virus at all |
| Infection risk | Slight (only in weak immune systems) | None |
| Immune response | Strong | Strong |
| Dose required | Usually 1–2 | 2 or more (boosters often needed) |
| Memory cells formed? | Yes ✅ | Yes ✅ |
| Example | MMR (measles, mumps, rubella) | Pfizer, Moderna COVID-19 |
✅ Summary:
- Live-attenuated vaccines use weakened microbes to trigger strong immunity (e.g., MMR)
- mRNA vaccines deliver genetic code for viral protein → no infection risk (e.g., COVID-19 vaccines)
- Both types give active immunity and lead to formation of memory cells
💡 Did You Know? mRNA vaccines were researched for decades before COVID but had no wide-scale rollout until the pandemic changed everything.
Live vaccines are some of the oldest and most reliable types still in use.
Herd Immunity (Thresholds & Ethical Dilemmas)
🧠 What is Herd Immunity?
Herd immunity happens when enough people in a population are immune to an infectious disease (through vaccination or previous infection), making it hard for the disease to spread even to those who aren’t immune.
📌 This protects:
- Babies (too young to be vaccinated)
- People with weakened immune systems
- People who can’t get vaccines for medical reasons
🔐 How Does Herd Immunity Work?
Imagine a virus trying to move from person to person. If most people it “tries to infect” are already immune, the virus can’t spread → the chain is broken
It’s like a fire running out of fuel – it dies out
📈 Herd Immunity Threshold (HIT)
The minimum % of immune people needed to stop disease spread.
It depends on how contagious a disease is.
More contagious = higher % needed.
🧮 Formula:
\[
\text{Herd Immunity Threshold} = 1 – \frac{1}{R_0}
\]
📊 Examples of Herd Immunity Thresholds
| Disease | R₀ (Infectiousness) | HIT (%) Needed |
|---|---|---|
| Measles | ~15 | ~95% |
| COVID-19 (original) | ~2.5 | ~60% |
| Polio | ~5–7 | ~80–86% |
| Influenza (Flu) | ~1.5 | ~33% |
💉 Herd Immunity & Vaccines
Vaccination is the safest way to build herd immunity:
- No need to get sick to gain protection
- Vaccines stimulate memory cells without causing disease
Natural infection = risky (can cause death or long-term illness)
Vaccination = controlled, safer route to immunity
⚖️ Ethical Dilemmas in Herd Immunity
While herd immunity can save lives, it also raises ethical questions:
1. Vaccine Refusal
- Dilemma: Should people be allowed to refuse vaccines when their choice can endanger others?
- Some argue: personal freedom
- Others argue: social responsibility
2. Vaccine Mandates
- Should governments force vaccinations during pandemics?
- Balance between:
- Public health safety
- Individual rights
3. Access & Equity
- Not all communities have equal access to vaccines.
- Herd immunity may fail if poor nations are left behind
4. Letting a Virus “Spread Naturally”
Sounds easy – but dangerous ⚠️
- Millions could die or suffer long-term effects
- Overwhelms healthcare systems
- Ethically unjustifiable when vaccines exist
✅ Summary Points:
- Herd immunity protects vulnerable individuals indirectly
- Depends on % of immune people (HIT varies by disease)
- Vaccination = safe + ethical route to herd immunity
- Ethical dilemmas:
- Right to refuse vs. public safety
- Fair vaccine access
- Limits of government power
💡 Did You Know? The measles virus is so contagious that even one sick child can trigger an outbreak in an under-vaccinated school
Some diseases like tetanus don’t spread person-to-person → no herd immunity applies
Antibiotic Resistance (Misuse & Consequences)
🧠 What Is Antibiotic Resistance?
When bacteria evolve mechanisms to survive exposure to an antibiotic that once killed them or stopped their growth. The result: medicines that used to work ➡️ stop working.
⚙️ How Does Resistance Develop?
| Source of Misuse | What Happens Biologically? | Examples |
|---|---|---|
| Incomplete courses | Sensitive bacteria die first, partially resistant ones survive, multiply | Stopping a 7-day amoxicillin course on Day 3 |
| Over-prescription | Exposure without real need accelerates selection | Antibiotics for common colds (viral!) |
| Self-medication / Wrong dose | Too low a dose = “training camp” for bacteria | Left-over pills shared with a friend |
| Agricultural overuse | Massive, constant low-dose exposure → farm “superbugs” | Tetracycline in poultry feed |
| Poor infection control | Resistant strains spread between patients | MRSA outbreaks in ICUs |
“M.I.S.U.S.E.” = Missed doses, Incorrect indication, Shared meds, Underdose, Stock animals, Environmental spread
🔬 Mechanisms Bacteria Use to Outsmart Drugs
- Enzyme production – e.g., β-lactamase cuts penicillin ring
- Efflux pumps – protein “pumps” eject the drug
- Target modification – mutate ribosome or cell-wall protein
- Biofilm formation – sticky layer shields community
- Horizontal gene transfer – swap resistance plasmids via conjugation
🚨 Consequences of Antibiotic Resistance
| Impact Area | Real-World Effect |
|---|---|
| Patient health | Longer illness, higher mortality (e.g., drug-resistant TB) |
| Surgery & chemo | Routine operations become risky (need effective prophylaxis) |
| Cost | Extended hospital stays + expensive second-line drugs |
| Global health | Spread of “superbugs” like MRSA, CRE, XDR-TB |
| Return to pre-antibiotic era | Simple infections could again be fatal |
🛡️ What Can We Do? (Stewardship Tips)
- Finish the full course as prescribed
- No antibiotics for viral infections (colds, flu)
- Never share or reuse old antibiotics
- Vaccinate – prevents infections, lowers antibiotic demand
- Hospital hygiene – hand-washing, isolation rooms
- Farm regulations – restrict growth-promoter antibiotics
- Surveillance – track resistance patterns globally
✏️ Summary
- Definition: Bacteria survive despite antibiotic → continue multiplying
- Key driver: Misuse/overuse in humans & animals
- Mechanisms: Enzymes, pumps, mutations, biofilms, gene transfer
- Consequences: Hard-to-treat infections, higher costs/deaths, threat to modern medicine
- Prevention: Responsible prescribing + stewardship programs