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Most childhood vaccines are 90–99% effective in preventing disease. Side effects are rarely serious.
The immune system needs 9.5 hours of sleep in total darkness to recharge completely.
The word drug comes from the Dutch word droog (meaning "dry"). For centuries, most drugs came from dried plants, hence the name.
A cataract is a clouding of the eyes' natural lens. As we age, some clouding of the lens may occur. The first sign of a cataract is usually blurry vision. Although glasses and other visual aids may at first help a person with cataracts, surgery may become inevitable. Cataract surgery is very successful in restoring vision, and it is the most frequently performed surgery in the United States.
Nearly 31 million adults in America have a total cholesterol level that is more than 240 mg per dL.