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After a vasectomy, it takes about 12 ejaculations to clear out sperm that were already beyond the blocked area.
More than 2,500 barbiturates have been synthesized. At the height of their popularity, about 50 were marketed for human use.
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 nineteen million Americans carry the factor V gene that causes blood clots, pulmonary embolism, and heart disease.
Interferon was scarce and expensive until 1980, when the interferon gene was inserted into bacteria using recombinant DNA technology, allowing for mass cultivation and purification from bacterial cultures.