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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.
Medication errors are three times higher among children and infants than with adults.
Most childhood vaccines are 90–99% effective in preventing disease. Side effects are rarely serious.
Certain chemicals, after ingestion, can be converted by the body into cyanide. Most of these chemicals have been removed from the market, but some old nail polish remover, solvents, and plastics manufacturing solutions can contain these substances.
There are over 65,000 known species of protozoa. About 10,000 species are parasitic.