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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.
In the United States, there is a birth every 8 seconds, according to the U.S. Census Bureau's Population Clock.
The lipid bilayer is made of phospholipids. They are arranged in a double layer because one of their ends is attracted to water while the other is repelled by water.
On average, someone in the United States has a stroke about every 40 seconds. This is about 795,000 people per year.
The familiar sounds of your heart are made by the heart's valves as they open and close.