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The human body produces and destroys 15 million blood cells every second.
When blood is exposed to air, it clots. Heparin allows the blood to come in direct contact with air without clotting.
The immune system needs 9.5 hours of sleep in total darkness to recharge completely.
Approximately 70% of expectant mothers report experiencing some symptoms of morning sickness during the first trimester of pregnancy.
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.