Vaccines are used to provide long-term immunity to many infectious diseases.They prevent epidemics. Mass vaccination at the start of an epidemic slows down the spread of the pathogen.When a significant number of the population have been vaccinated, the probability of the pathogen being transmitted to an unvaccinated person becomes very small.This is known as herd immunity.Vaccines may have to be updated during an epidemic because of the emergence of new strains by mutation.So far scientists have been unable to develop vaccines for malaria and HIV.
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Specification: OCR Biology A (H020), AS-level, 4.1.1 Communicable diseases, disease prevention and the immune system. Topic: Communicable Diseases.
Key terms in this lesson
- plasmid
- A small, circular loop of DNA, separate from the main chromosome, found in the cytoplasm of prokaryotic cells.
- gene
- A length of DNA that codes for a specific polypeptide.
More in Communicable Diseases
- Auto-Immune Diseases
- Natural Immunity
- Artificial Passive Immunity
- Artificial Active Immunity
- Sources of Medicines
- Drug Design
- Antibiotic Resistance
- MRSA and C. difficile
All 40 lessons in Communicable Diseases · All OCR AS-level Biology topics