The failure of Merck & Co.'s once-promising AIDS vaccine has cast a pall over research efforts and forced delays in trials of other experimental vaccines as scientists ponder what went wrong.
After more than two decades of work, vaccine researchers were hoping to be further along. Even if other vaccine initiatives eventually succeed, the arduous process of development and testing means that there won't be an immunization to prevent HIV for at least another decade, one top federal researcher says.
The Merck vaccine not only failed to protect participants in the trial, it also might have put them at a greater risk of contracting the virus, company officials said last week.
"The recent Merck trial results were a big blow to the field," said Dr. Gary Nabel, director of the National Institutes of Health's Vaccine Research Center in Bethesda.
He said few in the field believed that the vaccine would provide total immunity, but "it had absolutely no effect. We thought maybe it would have a little effect and maybe that would point us in some direction we could follow up on."
Instead of looking forward to the next vaccine candidate, scientists at the NIH and elsewhere must first look back to make sure that mistakes are not repeated. A large clinical trial involving human subjects being done by Nabel's center has been pushed back to mid-2008 while a half-dozen smaller trials in earlier testing phases have been paused.
The Merck results don't mean researchers are at a dead-end, several insisted. In the 1930s, two major vaccines for preventing the polio virus failed "miserably," said Mitchell Warren, executive director of the nonprofit AIDS Vaccine Advocacy Coalition.
"The world didn't say, let's abandon the search," he said. Two decades later, two vaccines were developed that led to the eradication of polio in the United States.
Merck was the only pharmaceutical company developing a vaccine - spending 10 years, untold millions of dollars and some top scientific talent toward that end - and a company official said last week that it has no other vaccine candidate in development. That removes a major player, though government money and foundation dollars are likely to keep flowing to others doing vaccine research.
The Merck failure also raises important scientific questions. In analyzing the results, the company said 49 cases of HIV infection were seen among 914 male volunteers after they got the vaccine, compared with 33 cases of HIV infection among the 922 male volunteers who got a placebo.
