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Vaccines prevent between 2.5 and 4 million deaths every year.
Oliver Wendell Holmes is credited with introducing the words "anesthesia" and "anesthetic" into the English language in 1846.
There are 20 feet of blood vessels in each square inch of human skin.
More than 150,000 Americans killed by cardiovascular disease are younger than the age of 65 years.
There are over 65,000 known species of protozoa. About 10,000 species are parasitic.
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