In the following passage, some words have been deleted. Read the passage carefully and select the most appropriate option to fill in each blank.

Claims have been made that vaccines are responsible for certain (1)__________ health conditions, particularly autism, speech disorders and inflammatory bowel disease. Some of those claims focused on thimerosal, a mercury-containing compound used as a preservative in vaccines. Some people believed that autism (2)__________ a form of mercury poisoning, caused specifically by thimerosal in childhood vaccines. Those claims have been discredited. Still, misinformation and fear generated by false claims about associations (3)__________ autism and vaccines had a significant impact on individuals’ perceptions about vaccine safety. (4)__________, most individuals in countries where vaccination is widespread have never personally experienced vaccine-preventable disease. Thus, the focus of concern for some people shifted from the negative effects of vaccine-preventable disease to the possible negative effects of the vaccines (5)__________.

Select the most appropriate option to fill in blank number 1.