Chickenpox

Chickenpox is a extremely infectious viral disease. More than 90% of non-immune contacts of a case of chickenpox will end up with symptomatic disease.

The community has mostly viewed chickenpox as a benign childhood disease. In the past there were “chickenpox parties” where families, friends and relatives intentionally exposed their children at one time. Studies undertaken in the 1990’s demonstrated increasing levels of immunity in different age cohorts with over 80% children immune by 15 years of age and over 90% by their mid-twenties. It was also recognized that the disease was worse in older people.

The quest for a vaccine started in the 1970’s and by the 1980’s it became a reality. The argument for vaccination focused on potentially avoidable deaths. Notifications in the USA exceeded more than 100 annually. Most deaths were associated with immune suppression, often in association with diseases of the blood like leukaemia. There were also many cases of congenital varicella syndrome where a non-immune woman becomes infected during early pregnancy. Australia had a very similar profile to the USA but fewer numbers. The burden of disease morbidity on families was also very significant.

Childhood vaccination for chickenpox was commenced in the USA in 1995. A single dose was recommended at 18 months of age.

The USA chickenpox vaccination program has been a remarkable success: more than 91 million cases of chickenpox have been prevented, together with more than 238,000 hospitalisations and almost 2,000 deaths. The net societal savings is estimated at $23 billion.

Chickenpox vaccine was first registered for use in Australia in 1999. Many families immediately took up the opportunity to vaccinate their children. It became funded under the National Immunisation Program in 2005. A single dose was given at 18 months. A funded, school-based catch-up program for children aged 10-13 years was started in 2006. With parental consent, the vaccine was provided to all children where there wasn’t a history of childhood chickenpox. If you were still at school in 2014 it is likely you have been vaccinated for chickenpox.

The majority of overseas travellers are either naturally immune to chickenpox (prior to the introduction of the vaccines) or currently vaccinated.  It is still possible to have a second dose of chickenpox, but the likelihood of significant disease is low.

The major concern is for those travellers who have negotiated childhood and adolescence and not experienced a bout of the disease or been vaccinated. Chickenpox is still a common disease in many overseas countries and the disease can be very unpleasant and scarring in older individuals. As such, chickenpox is routine travel vaccination for this group. A person with a negative disease history may still have experienced a bout of chickenpox. Fifty percent will find out they have had the disease following a blood test.