1. 1
   A Year 10 class is studying an outbreak of measles at a local primary school. Public health officials find that almost all of the affected children were the small number who had not received the MMR vaccine, while their classmates who had been vaccinated in early childhood remained healthy despite close, repeated contact with infected children.

   (a)

   Which type of pathogen causes measles?

   [1 mark]

   • ABacterium
   • BVirus
   • CProtist
   • DFungus

   (b)

   Which of these best describes how phagocytosis destroys a pathogen in the body?

   [1 mark]

   • AA white blood cell engulfs the pathogen and digests it
   • BA white blood cell produces a protein that binds specifically to antigens on the pathogen
   • CA white blood cell produces a chemical that neutralises toxins released by the pathogen
   • DA white blood cell divides repeatedly to form memory cells

   (c)

   Explain why the vaccinated classmates did not develop measles despite being in close, repeated contact with infected children.

   [2 marks]

   Total for question 1: 4 marks

2. 2
   A poultry farm experiences an outbreak of Salmonella food poisoning traced to birds' food being prepared in unhygienic conditions. Affected workers who ate the contaminated food develop a fever, abdominal cramps, vomiting and diarrhoea. Vets note that the birds themselves had all been vaccinated against Salmonella as chicks and remained free of symptoms.

   (a)

   Which type of pathogen causes Salmonella food poisoning?

   [1 mark]

   • AProtist
   • BVirus
   • CBacterium
   • DFungus

   (b)

   Which statement best explains why symptoms such as fever, abdominal cramps and diarrhoea occur after a person eats food contaminated with Salmonella bacteria?

   [1 mark]

   • AThe bacteria reproduce inside gut cells, causing the cells to burst
   • BThe bacteria invade and destroy the person's red blood cells directly
   • CThe bacteria produce antibodies that attack the gut lining
   • DToxins produced by the bacteria damage the body's tissues

   (c)

   Suggest why vaccinating the poultry against Salmonella, rather than treating them with antibiotics, is an effective way of preventing this disease in the birds.

   [2 marks]

   Total for question 2: 4 marks

3. 3
   A patient is diagnosed with HIV. Shortly after infection, they experience a mild flu-like illness, and for several years afterwards they have no further symptoms and continue with normal daily life. However, after around ten years without any antiretroviral treatment, the patient's white blood cell count falls significantly and they begin to suffer from several infections and illnesses, including a rare form of pneumonia, that would not normally affect a person with a healthy immune system.

   (a)

   Explain why a significant fall in the patient's white blood cell count makes them more likely to suffer from infections that would not affect a person with a healthy immune system.

   [3 marks]

   (b)

   Describe how HIV is spread between people, and explain why doctors were unable to use antibiotics to treat the patient's original HIV infection.

   [4 marks]

   Total for question 3: 7 marks

4. 4
   A country is planning a national vaccination programme against a serious viral disease. Public health data from other countries show that once vaccination uptake in the population reaches around 95%, cases of the disease fall dramatically, even among the small number of people who have not themselves been vaccinated. Some parents are hesitant to vaccinate their children because of concerns they have read on social media, while doctors argue that widespread vaccination is essential to protect vulnerable members of the community, such as babies and people with weakened immune systems, who cannot safely be vaccinated for medical reasons.

   (a)

   Explain in detail how vaccination protects an individual from becoming ill with this disease, including what happens in the body when the vaccine is first given, and what happens if the same pathogen later enters the body of a vaccinated person.

   [6 marks]

   (b)

   Explain how widespread vaccination across a population can protect even the individuals who have not themselves been vaccinated, and evaluate why public health officials might consider it important to increase vaccination uptake to around 95% in this country rather than settling for a lower uptake.

   [6 marks]

   Total for question 4: 12 marks

End of questions