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Most childhood vaccines are 90–99% effective in preventing disease. Side effects are rarely serious.
The B-complex vitamins and vitamin C are not stored in the body and must be replaced each day.
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.
As the western states of America were settled, pioneers often had to drink rancid water from ponds and other sources. This often resulted in chronic diarrhea, causing many cases of dehydration and death that could have been avoided if clean water had been available.
The Romans did not use numerals to indicate fractions but instead used words to indicate parts of a whole.