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Before a vaccine is licensed in the USA, the Food and Drug Administration (FDA) reviews it for safety and effectiveness. The CDC then reviews all studies again, as well as the American Academy of Pediatrics and the American Academy of Family Physicians. Every lot of vaccine is tested before administration to the public, and the FDA regularly inspects vaccine manufacturers' facilities.
The average human gut is home to perhaps 500 to 1,000 different species of bacteria.
After a vasectomy, it takes about 12 ejaculations to clear out sperm that were already beyond the blocked area.
The shortest mature adult human of whom there is independent evidence was Gul Mohammed in India. In 1990, he was measured in New Delhi and stood 22.5 inches tall.
The first documented use of surgical anesthesia in the United States was in Connecticut in 1844.