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Vaccines cause herd immunity. If the majority of people in a community have been vaccinated against a disease, an unvaccinated person is less likely to get the disease since others are less likely to become sick from it and spread the disease.
The first war in which wide-scale use of anesthetics occurred was the Civil War, and 80% of all wounds were in the extremities.
Sperm cells are so tiny that 400 to 500 million (400,000,000–500,000,000) of them fit onto 1 tsp.
Drying your hands with a paper towel will reduce the bacterial count on your hands by 45–60%.
Malaria mortality rates are falling. Increased malaria prevention and control measures have greatly improved these rates. Since 2000, malaria mortality rates have fallen globally by 60% among all age groups, and by 65% among children under age 5.