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Most childhood vaccines are 90–99% effective in preventing disease. Side effects are rarely serious.
Aspirin is the most widely used drug in the world. It has even been recognized as such by the Guinness Book of World Records.
Though the United States has largely rejected the metric system, it is used for currency, as in 100 pennies = 1 dollar. Previously, the British currency system was used, with measurements such as 12 pence to the shilling, and 20 shillings to the pound.
Vampire bats have a natural anticoagulant in their saliva that permits continuous bleeding after they painlessly open a wound with their incisors. This capillary blood does not cause any significant blood loss to their victims.
The horizontal fraction bar was introduced by the Arabs.