NEW YORK (AP) -- A British biotechnology company Tuesday reported "encouraging" results from an early-stage trial of its smallpox vaccine.

Acambis PLC compared its ACAM1000 vaccine and the vaccine widely used during the worldwide eradication program, Dryvax.

In the trial, 30 people were given a standard dose of Dryvax and the other 30 people were given an equivalent dose of ACAM1000.

Within 10 days of vaccination, all of the people who received the ACAM1000 vaccine reported a "take," the pock-mark on the skin that indicates immunity to the disease,

All except one of the Dryvax-treated subjects had successful results. The size and appearance of the "takes" were identical for both treatments.

Patients injected with the ACAM1000 vaccine reported no serious or unexpected side effects, but one subject in the Dryvax group developed a non-healing pock-mark at the site of inoculation.

Following the results, the company said it started a second, open-label trial, using 70 subjects, to test further the vaccine's safety and success in immunity.

A month after the terrorist attacks last year, the Department of Health and Human Services asked firms interested in making a smallpox vaccine to show how they can develop, make and deliver up to 250 million doses of smallpox vaccine within a 12-month period.

In October, American Home Products Corp. said it's Wyeth-Ayerst Laboratories unit planned to develop and manufacture a new smallpox vaccine, if its plans were approved by the U.S. government.

Wyeth-Ayerst began making DryVax, in 1944, but discontinued production in the mid-1980s after the World Health Assembly certified the world free of naturally occurring smallpox.

Copyright 2002 The Associated Press. All rights reserved.