Varicella vaccine

Varilix (SmithKline Beecham)
vials containing a powder pellet for reconstitution
Approved indication: immunisation
Australian Medicines Handbook Section 20.1

Chickenpox is usually a mild childhood infection. It can, however, be fatal in immuno compromised patients. In the USA the cost of managing chickenpox is estimated to be US$400 million.1 Universal vaccination is now recommended for all American children.

The vaccine which has been approved for use in Australia is a live attenuated strain of the varicella-zoster virus. A single dose is recommended for children more than nine months old. Older children and adults have two doses at least six weeks apart. The deltoid area is the preferred site for the subcutaneous injection.

In children a single dose of vaccine has an efficacy of 88%. Children who catch chickenpox despite vaccination appear to develop an attenuated infection.

Injection site reactions occur in 27% of cases. Some vaccinees develop a mild varicella-like disease within a month.

Although varicella vaccines have been available overseas for several years, there are unanswered questions about their role. The duration of immunity is unknown; will immunising children result in more infections in later life? It will be many years before we know if the vaccine influences the incidence and severity of shingles. An economic analysis in the USA has found that the vaccine may not be cost-beneficial from the perspective of `payers' such as governments or health funds. For every dollar spent the payer only saves US 90 cents. However, from a societal perspective, including costs such as time lost from work, the community saves US$5.40 for every dollar spent.1 A New Zealand study found similar results. For every dollar spent the payer saves NZ 67 cents, but society saves NZ$2.79.2

References

  1. Strassels SA, Sullivan SD. Clinical and economic considerations of vaccination against varicella. Pharmacotherapy 1997;17:133-9.
  2. Scuffham P, Devlin N, Eberhart-Phillips J, Wilson-Salt R. The cost-effectiveness of introducing a varicella vaccine to the New Zealand immunisation schedule. Soc Sci Med 1999;49:763-79.

Some of the views expressed in the following notes on newly approved products should be regarded as preliminary, as there may have been limited published data at the time of publication, and little experience in Australia of their safety or efficacy. However, the Editorial Executive Committee believes that comments made in good faith at an early stage may still be of value. Before new drugs are prescribed, the Committee believes it is important that more detailed information is obtained from the manufacturer's approved product information, a drug information centre or some other appropriate source.