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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.
In the ancient and medieval periods, dysentery killed about ? of all babies before they reach 12 months of age. The disease was transferred through contaminated drinking water, because there was no way to adequately dispose of sewage, which contaminated the water.
People with high total cholesterol have about two times the risk for heart disease as people with ideal levels.
The ratio of hydrogen atoms to oxygen in water (H2O) is 2:1.
The human body produces and destroys 15 million blood cells every second.