Question 1: Define vaccination and explain how it helps to protect individuals and populations from disease.

Answer: Vaccination involves introducing a weakened or inactive form of a pathogen into the body to stimulate the immune system to produce an immune response. It helps protect individuals by building immunity and contributes to herd immunity, reducing disease spread in the population.

Question 2: Describe the role of memory cells in the immune response after vaccination.

Answer: Memory cells are a type of white blood cell that remain in the body after vaccination. They enable the immune system to recognise the pathogen quickly if exposed again, leading to a faster and stronger immune response.

Question 3: Explain why vaccines are sometimes administered in multiple doses.

Answer: Multiple doses of vaccines are given to ensure the immune system is sufficiently stimulated to produce a strong and lasting immunity, often with booster shots that reinforce the immune memory.

Question 1: A vaccine has an efficacy rate of 85%. If 10,000 people are vaccinated, how many are expected to become immune due to the vaccine? (Use the formula: Number immune = Total vaccinated × efficacy rate).

Answer: 8500

Question 2: Calculate the percentage increase in vaccine coverage if the number of vaccinated individuals rises from 8,000 to 12,000, assuming the same efficacy rate. Show your calculation.

Answer: Percentage increase = [(12000 - 8000) / 8000] × 100 = 50%

Question 1: Identify three variables that should be controlled in a clinical trial testing a new vaccine, and explain why controlling each is important.

Answer: Variables to control include: 1) Age of participants, to ensure consistent immune response; 2) Health status, to avoid confounding effects of illness; 3) Dosage of vaccine, to standardise immune stimulation. Controlling these variables ensures reliable and valid results.

Question 1: In a study, 5,000 individuals received a new vaccine. Out of these, 4,250 developed immunity after one dose. Calculate the vaccine's effectiveness and interpret what this means in terms of herd immunity.

Answer: Vaccine effectiveness = (Number immune / Total vaccinated) × 100 = (4250 / 5000) × 100 = 85%. This suggests that the vaccine is highly effective, contributing significantly to herd immunity by reducing disease transmission.

Question 1: Describe the process by which a vaccine stimulates the immune system to produce immunity, including the roles of different immune cells. (6 marks)

Answer: When a vaccine is administered, it introduces antigens that mimic a pathogen. Phagocytes engulf these antigens and present them to helper T cells, which activate B cells. B cells produce specific antibodies and form memory cells. Cytotoxic T cells may also be activated to destroy infected cells. The combined response results in immunity, with memory cells enabling faster response upon future exposure.

Question 1: Discuss how vaccines have contributed to the eradication of smallpox and the challenges faced in eradicating other diseases like polio.

Answer: Vaccines led to the eradication of smallpox by providing immunity to all populations, reducing transmission, and enabling global vaccination campaigns. Challenges in eradicating diseases like polio include vaccine hesitancy, logistical issues in remote areas, and mutations of the virus that complicate vaccine development.