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Most childhood vaccines are 90–99% effective in preventing disease. Side effects are rarely serious.
According to the National Institute of Environmental Health Sciences, lung disease is the third leading killer in the United States, responsible for one in seven deaths. It is the leading cause of death among infants under the age of one year.
Pope Sylvester II tried to introduce Arabic numbers into Europe between the years 999 and 1003, but their use did not catch on for a few more centuries, and Roman numerals continued to be the primary number system.
When blood is exposed to air, it clots. Heparin allows the blood to come in direct contact with air without clotting.
The familiar sounds of your heart are made by the heart's valves as they open and close.