Acambis begins testing West Nile vaccine in older adults

The trial is designed to evaluate the safety, tolerability and immunogenicity of ChimeriVax-West Nile in older adults and is being conducted in the US. The randomized, double-blind, placebo-controlled study is the second part of a phase II trial evaluating the vaccine.

Previously, Acambis had reported encouraging results from the first part of the phase II trial, which involved younger adults aged 18-40 years. Over 97% of subjects who received a single dose of ChimeriVax-West Nile developed neutralizing antibodies above the predefined cut-off level 28 days after vaccination. The majority of adverse events were mild in nature.

Since the West Nile virus emerged in the US in 1999, there have been almost 24,000 cases and 946 deaths. There is currently no vaccine against the disease.

Acambis' CEO Gordon Cameron said: “Acambis is the leader in developing a West Nile virus vaccine and we've taken another important step by testing ChimerVax-West Nile in older adults, the group most at risk of severe disease from West Nile virus infection.”