Chickenpox (Varicella) - Diseases and Vaccines

Immunisation
Chickenpox (Varicella)

Virus
Chickenpox is a highly infectious viral infection. It is usually a mild disease however the severity and risk of complications can be greater in adults.
In New Zealand it is estimated that each year there are approximately 50,000 chickenpox infections, of which 150-200 result in hospitalisation, 1-2 cases result in long-term disability or death

How it is spread
Chickenpox is spread by coughing and sneezing and also by direct contact with weeping blisters. It is highly infectious, from up to 2 days before the appearance of the rash until blisters have crusted (usually about 5-7 days). If one person has chickenpox, about 85% of their close contacts will get it too, unless they have already had the disease or been vaccinated.

Symptoms and illness
Chickenpox starts with a fever and/or general unwellness for a day or two followed by a rash. The rash starts out as small spots before changing to blisters with a red base. The rash usually starts on the head and face before spreading to the trunk and then the limbs.

Severe risks associated with chickenpox

Mortality in normal healthy children is less than 2 per 100,000 cases, increasing up to 15 fold in adults.
The severity and risk of complications is greater for adults. Complications can include severe tissue infection, low platelet count, pneumonia and inflammation of the joints, kidneys and liver.
The lesions may leave mild scarring in some skin types. Shingles is a long-term complication that is not immediately apparent but can appear decades after the disease.

Severe risks associated with the vaccine

Seizure caused by fever (1:1,000 or less)
Pneumonia (extremely rare)

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Page last updated: 13 June 2008