Question 28
Jonas Salk developed the polio vaccine in 1952. In 1954, the March of Dimes organization vaccinated nearly two million school children against the disease.
According to the graph, what were the results of the vaccination between 1954 and 1960?
a
The rate of polio remained the same.
b
The rate of polio decreased.
c
The rate of polio decreased, then increased.
d
The rate of polio increased.