The disease

What is chickenpox?

Chickenpox is an infection caused by the varicella virus, and it is highly contagious. It can spread in one of three ways: by coughing or sneezing, physical contact with broken blisters, or by virus particles from the blisters that are sprayed in the air. The rash of chickenpox begins as red bumps that turn into blisters that cover the entire body. As many as 300-500 blisters can occur during a single infection.

Chickenpox is usually a relatively benign infection. However, chickenpox infections can have severe complications. About 1 of every 1,000 children infected with varicella will develop severe pneumonia (infection of the lungs) or encephalitis (infection of the brain). In addition, about 1of every 50 women infected with varicella during their pregnancy will deliver children with birth defects. These birth defects include mental retardation and shortened or atrophied limbs. Finally, a bacterium called Group A streptococcus, commonly known as “flesh-eating” bacteria, can enter through the skin during a varicella infection and cause severe, and sometimes fatal, disease.

How contagious is chickenpox?

Chickenpox is very contagious. If 100 people are sitting in a room together for several hours talking and one of them has chickenpox and the other 99 have never been infected with chickenpox or vaccinated with the chickenpox vaccine, about 85 of the remaining 99 will get chickenpox.

Who should get the chickenpox vaccine?

The varicella vaccine is given to children between 12 and 15 months and again between 4 and 6 years of age. Children, adolescents and young adults who have received only one dose should get a second dose. For previously unimmunized adolescents (13 to 18 years old) or adults, the vaccine is given as a series of two shots, separated by four to eight weeks.