1. What Are Vaccines?

• A vaccine is a substance that prepares the body’s immune system to recognize and fight specific pathogens (like viruses or bacteria).
• It usually contains weakened, inactivated, or parts of the pathogen (antigens).

2. How Do Vaccines Work?

• Vaccine introduces antigens into the body.
• Immune system produces antibodies against the antigen.
• If the real pathogen infects later, the immune system remembers and fights quickly → Immunity is developed.

✅ Vaccines are preventive – they protect you before you get infected.

3. Types of Vaccines

Type	Description	Examples
Live attenuated	Weakened but living microbes → strong, long-lasting immunity	MMR, oral polio (OPV)
Inactivated (killed)	Microbe killed by heat/chemicals → safer, weaker response	Polio (IPV), rabies
Toxoid	Inactivated toxins → trains immune system against bacterial toxins	Tetanus, diphtheria
Subunit / Recombinant	Only fragments (antigens) of pathogen used → no risk of infection	Hepatitis B, HPV
mRNA	Contains genetic code to produce antigen in host cells	Pfizer-BioNTech (COVID)
Viral vector (carrier)	Uses a harmless virus to deliver antigen gene to host cells	AstraZeneca, Sputnik V
Genetically modified bacteria	Bacteria genetically engineered to carry and deliver vaccine antigens	Sputnik V (vector-based) and experimental types in development

4. What Are Antibiotics?

• Antibiotics are medicines that kill or stop the growth of bacteria.
• They do not work on viruses.

5. How Do Antibiotics Work?

• They target specific bacterial features, such as:
• Cell wall (e.g., Penicillin)
• Protein synthesis
• DNA replication
• This stops the bacteria from growing or kills them directly.

6. Examples of Antibiotics

Antibiotic	Action	Example Use
Penicillin	Blocks cell wall synthesis	Strep throat, skin infections
Amoxicillin	Similar to penicillin	Ear infections, pneumonia
Tetracycline	Inhibits protein synthesis	Acne, respiratory infections
Ciprofloxacin	Stops DNA replication	Urinary tract infections

7. Antibiotic Resistance

• Happens when bacteria mutate and become unaffected by antibiotics.
• Caused by:
• Overuse or misuse of antibiotics
• Not finishing prescribed doses
• Leads to “superbugs” that are hard to treat

❌ Antibiotics should only be taken with a prescription and never for viral infections.

8. Comparison Table: Vaccines vs Antibiotics

Feature	Vaccines	Antibiotics
Type	Preventive	Curative (after infection)
Targets	Viruses or bacteria (specific)	Bacteria only
Immune response	Yes – trains immune system	No – works directly on bacteria
Examples	MMR, COVID-19, Tetanus	Penicillin, Amoxicillin, Tetracycline

9. Key Vocabulary

• Antigen: A molecule from a pathogen that triggers an immune response
• Antibody: A protein produced by white blood cells that attacks antigens
• Pathogen: A microbe that causes disease
• Immunity: Resistance to a disease, usually from past exposure or vaccination
• Resistance: The ability of bacteria to survive antibiotics

Written by Kasiban Parthipan