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.
A vaccine to protect children against chickenpox was first licensed in 1995. Children who have never had chickenpox should routinely be administered two doses of varicella vaccine with the first dose at 12 to 15 months and the second dose at four to six years of age.hickenpox is a common childhood illness with 90 percent of the cases occurring in children younger than ten years of age. Before the availability of the varicella vaccine in the U.S., almost everyone developed chickenpox. Most people who are vaccinated will not get chickenpox.