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Vaccines prevent between 2.5 and 4 million deaths every year.
A cataract is a clouding of the eyes' natural lens. As we age, some clouding of the lens may occur. The first sign of a cataract is usually blurry vision. Although glasses and other visual aids may at first help a person with cataracts, surgery may become inevitable. Cataract surgery is very successful in restoring vision, and it is the most frequently performed surgery in the United States.
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.
More than 2,500 barbiturates have been synthesized. At the height of their popularity, about 50 were marketed for human use.
About 3% of all pregnant women will give birth to twins, which is an increase in rate of nearly 60% since the early 1980s.