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Most childhood vaccines are 90–99% effective in preventing disease. Side effects are rarely serious.
Cyanide works by making the human body unable to use oxygen.
The familiar sounds of your heart are made by the heart's valves as they open and close.
Although puberty usually occurs in the early teenage years, the world's youngest parents were two Chinese children who had their first baby when they were 8 and 9 years of age.
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.