Question

the graph gives the number of varicella (chicken pox) cases between 1972 and 2011. varicella is an infectious disease caused by a virus. the disease causes rash, itching, and fever in patients. the varicella vaccine was introduced in 1995. what can you conclude about the vaccine?
varicella (chickenpox) cases 1972 - 2011
a. it was successful in eradicating chicken pox from the united states.
b. it had no effect on the rate of chicken pox cases in the united states.
c. it caused a 10% decrease in the number of chicken pox cases in the united states from 1995 to 2011.
d. it actually caused a large drop in chicken pox cases in the united states, and the rate continued to decrease.

Explanation:

Before 1995, the number of varicella cases fluctuated within a relatively high - range. After 1995 when the vaccine was introduced, there was a significant and continuous drop in the number of cases. However, the number did not reach zero.

Answer:

D. It initially caused a large drop in chicken - pox cases in the United States, and the rate continued to decrease.