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The immune system needs 9.5 hours of sleep in total darkness to recharge completely.
If all the neurons in the human body were lined up, they would stretch more than 600 miles.
Each year in the United States, there are approximately six million pregnancies. This means that at any one time, about 4% of women in the United States are pregnant.
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.
Cancer has been around as long as humankind, but only in the second half of the twentieth century did the number of cancer cases explode.