After the failure of Merck & Co.’s HIV vaccine trial last September—an effort that may have made trial participants even more vulnerable to infection—a separate trial conducted by the United States National Institutes of Health Vaccine Research Center will be scaled back considerably, Bloomberg reports (bloomberg.com, 3/24).

According to the article, this trial was originally slated to test a potential AIDS vaccine on 8,500 people in the U.S. and Africa. Now it may be studied in only 2,000 participants from both regions.

In light of the Merck trial, many AIDS experts are not convinced any real progress has been made in vaccine development in the 25 years since the virus was discovered.

However, some are optimistic, claiming that the Merck trial was an important stepping-stone in the search for an HIV vaccine. Harvard Medical School AIDS researcher Bruce Walker is planning to study why the Merck trial was unsuccessful and how those missteps may be corrected.

“In every organization, it’s useful to stop and take stock, particularly when you’ve had an unanticipated result,” he said. “That’s what this is about.”