The return of measles
317 words over 30 numbered lines, then 6 parts worth 13 marks (Modular Unit 2 (4WBI2) style, 12–13 marks). Read the article, answer each part, then open its mark scheme and set your mark.
Illustrative article written for Scholar Lab, not a Pearson text. The biology is real; the studies, people and figures are invented or rounded for practice.
The return of measles
Measles is caused by a virus that spreads in tiny droplets when an
infected person coughs or sneezes. It is one of the most infectious
diseases known: one person with measles can pass it to around fifteen
others who have no protection. Most children recover after a week of
fever and rash, but some develop pneumonia or swelling of the brain.
When the measles virus enters the body, white blood cells respond.
Phagocytes engulf and digest pathogens. Lymphocytes produce antibodies
that fit the antigens on the surface of the virus. This takes several
days, which is why a person is ill before they start to recover. After
the infection, some lymphocytes remain in the blood as memory cells.
A vaccine contains a weakened form of the virus that cannot cause the
disease. It stimulates the same response, so the person becomes immune
without being ill. Figure 1 shows the antibody concentration in a
child who was vaccinated on day 0 and then came into contact with
measles on day 40.
Some people cannot be vaccinated, such as babies under one year old
and people whose immune system is weakened by cancer treatment. They
are protected only if almost everyone around them is immune, so that
the virus cannot spread from person to person. Health experts estimate
that about 95% of a population needs to be immune to stop measles from
spreading.
In an illustrative town where many parents had missed their children’s
vaccinations, an outbreak began in a secondary school. Of the 1,240
pupils at the school, 1,054 had received both doses of the vaccine.
Twenty-three pupils caught measles, and none of them had been fully
vaccinated.
Doctors cannot treat measles with antibiotics. Instead, they give
fluids and rest, and they watch carefully for complications. Some
children with measles do need antibiotics, because a bacterial
infection of the lungs or ears can develop while they are weak.
Figure 1 Antibody concentration in the blood of a vaccinated child
Background: World Health Organization, Measles fact sheet (2024). The article text, the school and the figures are illustrative.
Read the article and study the figure. Use the information in the article and your own knowledge to answer the questions. The lines in brackets show where to look; select them to highlight the text.
Use the information in the article and your own knowledge to answer the questions. The lines in brackets show you where to look; select them to highlight the text.
State what is meant by the term pathogen.
(1)Describe how a phagocyte destroys a pathogen.
(2)Explain how vaccination protects a child from measles.
(3)Compare the antibody response after vaccination with the response after exposure to the virus on day 40, shown in Figure 1.
(3)Calculate the percentage of pupils at the school who had received both doses of the vaccine. Give your answer to one decimal place.
(2)Explain why a high level of vaccination in a population protects babies who are too young to be vaccinated.
(2)Total for this question: 13 marks
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