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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.
Nearly 31 million adults in America have a total cholesterol level that is more than 240 mg per dL.
According to the American College of Allergy, Asthma & Immunology, more than 50 million Americans have some kind of food allergy. Food allergies affect between 4 and 6% of children, and 4% of adults, according to the CDC. The most common food allergies include shellfish, peanuts, walnuts, fish, eggs, milk, and soy.
There are over 65,000 known species of protozoa. About 10,000 species are parasitic.
The ratio of hydrogen atoms to oxygen in water (H2O) is 2:1.