Two doses of varicella vaccine protect better than one, confirms a US report on the national vaccination programme published this week.

The United States introduced vaccination of children against chickenpox in 1995. One dose was recommended for children aged 12 months to 12 years and two doses for susceptible adolescents and adults. The vaccine policy was changed in 2006 to recommend a second vaccination for all.

The review by researchers at the Centers for Disease Control and Prevention (CDC) and Tufts University Medical School in Boston found that the vaccination programme had resulted in "a dramatic decline in disease" (Pediatrics 2008;122:744-51, doi:10.1542/peds.2008-0567).

It added: "Even with high vaccination coverage, the effectiveness of one dose of vaccine did not generate sufficient population immunity to prevent community transmission."

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