Most children recover well from a bout of chicken pox, It is not usually a life threatening disease. They may be off school for 7-10 days and have up to 250-500 itchy red blisters and spots; they recover well and have just a few scars.
Varicella or chicken pox is highly infectious. It spreads rapidly through households, and is very common with infection of up to 90% of vulnerable individuals who come into contact with the virus

 However occasionally severe complications such as meningitis and pneumonia occur especially as one gets older. The rate of admissions to hospital for treatment of varicella is 900% higher in adults although 90% of are people affected before adolescence.

10-20% of people who had had chickenpox will eventually develop shingles (a condition characterised by numbness, itching, or severe pain that may last for many weeks and may reoccur.

In pregnancy there is a fear of severe damage to the developing baby as well as complications with the mother
It is a course of two vaccines with about 6 weeks between doses

Until recently it was recommended that children should just have one vaccine, with the over twelve years and adults having two injections. The Department of Guidelines were changed in February 2010 so here at The Travel Clinic Ltd we are recalling all children to have their second dose of varicella vaccine
Later this Spring 2010 a vaccination against shingles will be released, the DOH are looking at vaccinating elderly people with the vaccine first as they are extremely vulnerable, this vaccine will be available from The Travel Clinic Ltd as soon as it is released.
 
http://www.patient.co.uk/doctor/Chickenpox-(Varicella).htm is a useful source of information