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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.
Thyroid conditions cause a higher risk of fibromyalgia and chronic fatigue syndrome.
More than 2,500 barbiturates have been synthesized. At the height of their popularity, about 50 were marketed for human use.
Malaria was not eliminated in the United States until 1951. The term eliminated means that no new cases arise in a country for 3 years.
Approximately one in three babies in the United States is now delivered by cesarean section. The number of cesarean sections in the United States has risen 46% since 1996.