Varicella vaccine given subcutaneously (under the skin). It is recommended for all children under 13 and for everyone 13 or older who has never had chickenpox. In the United States two doses are recommended. In the first case a first dose is administered at 12 to 15 months and a second dose at age 4–6 years. For people older than 13 the two doses are administered 4 to 8 weeks apart. The varicella vaccine did not become widely available in the United States until 1995. In the UK, the vaccine is only recommended in people who are particularly vulnerable to chickenpox. The
Contagious disease illustrated classically by tuberculosis, which is clearly transmissible from person to person, but was not classically considered a contagious disease. In the present day, most sexually transmitted diseases are considered contagious, but only some of them are subject to medical isolation. Originally, the term referred to a "contagion" (a derivative of 'contact') or disease transmissible only by direct physical contact. In the modern day, the term has sometimes been broadened to encompass "any" communicable or infectious disease. Often the word can only be understood in context, where it is used to emphasise very infectious, easily transmitted, or especially severe communicable