Two graphs are plotted below showing trends related to pertussis (whooping cough) in the UK from 1960 to 2020:
Use the graphs to answer the following questions:
a.[1]
What year was the pertussis vaccine first introduced?
b.[3]
Describe the trend in the annual number of pertussis cases from 1960 to 1985.
c.[1]
In 2005, a scientific paper was published suggesting a link between the vaccine and a health concern. What happened to the percentage of infants vaccinated against pertussis after 2005?