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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 Babylonians wrote numbers in a system that used 60 as the base value rather than the number 10. They did not have a symbol for "zero."
When blood is exposed to air, it clots. Heparin allows the blood to come in direct contact with air without clotting.
In 2012, nearly 24 milliion Americans, aged 12 and older, had abused an illicit drug, according to the National Institute on Drug Abuse (NIDA).
Children with strabismus (crossed eyes) can be treated. They are not able to outgrow this condition on their own, but with help, it can be more easily corrected at a younger age. It is important for infants to have eye examinations as early as possible in their development and then another at age 2 years.