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Most childhood vaccines are 90–99% effective in preventing disease. Side effects are rarely serious.
The familiar sounds of your heart are made by the heart's valves as they open and close.
Vaccines prevent between 2.5 and 4 million deaths every year.
Urine turns bright yellow if larger than normal amounts of certain substances are consumed; one of these substances is asparagus.
The immune system needs 9.5 hours of sleep in total darkness to recharge completely.
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