Rules for chemical formulas (Back to search) 1  Enter a sequence of element symbols followed by numbers to specify the amounts of desired elements (e.g., C6H6). 2  Use correct case for element symbols. 3  Elements may be in any order.  If only one of a given atom is desired, you may omit the number after the element symbol.
Half of all varicella zoster cases occur in children between the ages of 5 and 9. It has been estimated that, before the chickenpox vaccine was introduced in the U.S. in 1995, only 10 percent of Americans over the age of 15 had never had chickenpox.
1971 was the year in which the Surgeon General of the United States Public Health Service, the Redbook Committee of the American Academy of Pediatrics, and the Territorial Health Officers agreed that the time had come to discontinue routine primary smallpox vaccination for American children.es there is in the early 1700's Dr. Edward Jenner had discovered that cows had cowpox so he got some cow pox and tested it on a local boy who then became ill for a few days b â¦ ut then after that he had became immune to smallpox! 3 people found this useful.