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Most childhood vaccines are 90–99% effective in preventing disease. Side effects are rarely serious.
Prostaglandins were first isolated from human semen in Sweden in the 1930s. They were so named because the researcher thought that they came from the prostate gland. In fact, prostaglandins exist and are synthesized in almost every cell of the body.
Pregnant women usually experience a heightened sense of smell beginning late in the first trimester. Some experts call this the body's way of protecting a pregnant woman from foods that are unsafe for the fetus.
There are over 65,000 known species of protozoa. About 10,000 species are parasitic.
The Romans did not use numerals to indicate fractions but instead used words to indicate parts of a whole.