'Good mix' at conference shows consensus
'Good mix' at conference shows consensus
Not suggesting abandoning DOT, experts say
An international conference intended to help build national consensus around a campaign for a new TB vaccine had the hoped-for effects, say organizers. The National Vaccine Program Office had called the conference, held in San Francisco in late August.
Perhaps most significant was the presence of more than a dozen vaccine industry representatives, who until lately have been reticent to overtures from TB experts to increase interest in vaccine research and development. Organizers say they were also heartened by the way the conference pulled together a cross-section of TB experts, including basic researchers and TB controllers; plus representatives from developed and developing countries alike.
"Everyone provided lessons from their own perspective, and it was a mixed group, which is just what we'd hoped for," says Ann Ginsberg, MD, PhD, head of the respiratory diseases branch of the division of microbiology and infectious diseases at the National Institute of Allergy and Infectious Diseases (NIAID) at the National Institutes of Health in Bethesda, MD.
It will take an investment of at least $800 million over the next 20 years to produce a new vaccine against TB, participants heard. But the pay-off would be the aversion of as many as 135 million cases of TB and 40 million deaths over the next half-century.
Those figures come from the NIH's blueprint plan for TB vaccine development, which made its national debut at the conference. (See related story, p. 117.) Speakers from other fields, including HIV/AIDS, talked about their own experiences with vaccine development and trials for candidate vaccines.
Trials, yes, but which kind?
Trials were an especially important agenda item. "You can decided ahead of time who needs a vaccine, and try to develop something that fills the bill," says Ginsberg. "But vaccine development is empiric." That means, in practice, that researchers won't know how a particular candidate works until it's already well into the trials process. "People have a lot of hypotheses about how their favorite candidates might work," she adds. "But the answers we get will depend on what questions we ask, and what trials we design."
Thus, trials can ask whether a candidate works to protect people from infection by inoculating those who are still uninfected and following them for 30 years; or they can ask whether the vaccine protects people already infected from developing active disease and follow subjects for a shorter period of time. A whole-population trial could, by inoculating both kinds of subjects, ask both questions and give both answers at different times, she adds.
Obviously, post-infection trials won't take as long to complete as pre-infection trials. One way to lessen follow-up even more would be to design a post-infection trial for a specific cohort known to be at high risk for progression to active disease. Such cohort trials could focus on AIDS patients, perhaps, or South African miners, who are also known to experience an unusually high rate of TB disease.
Even though the consensus among TB experts is that current TB control tools, including directly observed therapy, short-course (DOTS), can no longer be considered sufficient for eliminating TB in this country, conference speakers were at pains to emphasize that they still strongly support the use of such tools.
"We had lots of people from TB control saying that DOTS is great, but we can't eliminate TB with just DOTS. And we had people from research saying yes, we need a vaccine, but we also need DOTS," says Ginsberg. The World Health Organization (WHO), which has pushed especially hard for the adoption of DOTS worldwide, was well-represented at the conference, Ginsberg adds. Along with conference presenter Paul Nunn, MD, chief of research and surveillance for WHO's global TB program, WHO sent several representatives from Immunology of Mycobacterial Diseases (IMMYC), a steering committee charged with setting priorities and directing research for vaccines for TB and leprosy.
War stories from other fields
Several experts from outside the field of myco-bacteriology were on hand to share war stories from other campaigns to develop vaccines. A vaccine for Hepatitis B can be beneficial in both pre-exposure and post-exposure settings, explained Harold Margolis, MD, chief of the hepatitis branch at the Centers for Disease Control and Prevention. That suggests that the same TB vaccine could, in theory, be found that might protect subjects who are not yet infected, and those who already have been exposed.
There's a difference, though, Margolis adds: the Hepatitis B vaccine currently in use isn't what could be called a therapeutic vaccine, one that works in someone who's already been infected; rather, it works to prevent infection and primary disease from establishing itself in the first place.
"There was a wonderful spirit of cooperation among the various groups," adds Ginsberg. "We got lots of fresh ideas and saw some new faces. We heard that it'll be a long hard haul, but that ultimately, developing a TB vaccine is an achievable goal."
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