Conference examines how to sort out candidates
Need for evaluation urgent for vaccines
The urgent need for a reliable way to sift through all the TB candidate vaccines that are being developed has prompted the National Vaccine Program Office (NVPO) to convene a symposium in San Francisco devoted to the subject. The conference has been scheduled for Aug. 26-28.
"Our director decided TB was really an area where we needed to push forward," says Dan Salmon, MPH, policy fellow for the NVPO, a division of the U.S. Department of Health. "We urgently need a more effective vaccine for TB. But for a lot of reasons, this vaccine is going to be especially challenging to evaluate."
With interest in finding a TB vaccine exceptionally high, and laboratories virtually awash in new technologies, research groups are churning out lots of new candidates, Salmon says. Today there are almost 100 contenders; but the task of evaluating them will be a tough one, says Salmon.
One of the biggest problems is the widespread use in high-incidence countries of BCG (bacille Calmette-Guerin vaccine), which creates a host of complications. "Would a new vaccine be something that's given on top of BCG?" asks Salmon. "Or in place of it? If it's in place of BCG, and you're working in a high-incidence country, how do you do that in an ethical manner?" That is, do researchers substitute a vaccine that may not work at all, for BCG, which works at least some of the time?
TB's long latency period poses additional problems, making evaluation much more expensive than with other diseases. "You're talking about a long-term effort, not something that you can evaluate in a year or two," Salmon says.
Rich country/poor country dilemmas
Rich country/poor country disparities promise to supply the ingredients for more ethical potholes. "You probably wouldn't want to test a vaccine in America, since - unless you're talking about homeless people or HIV-positive people - there's simply not a lot of disease in this country," says Salmon.
What that means is that a vaccine which has been developed in the United States will probably be tested on people who live in a high-incidence, developing country. That describes the scenario with HIV vaccine candidates, of course. Presumably, testing a TB candidate vaccine will elicit the same kind of highly charged, emotional reactions raised by field-testing for HIV-related agents in poor countries. "We need to talk to the HIV people about the obstacles they're encountering, and how they're attempting to overcome them," says Salmon.
Symposium organizers say they're also hoping to sow some fresh ideas, by bringing in specialists from other fields. At press time, that included, for example, a veterinarian from New Zealand, Frank Griffin, DVM, who was scheduled to talk about veterinary TB vaccine development. David Klein, PhD, is scheduled to explain how the pertussis vaccine was developed in the absence of reliable animal models - one drawback with which TB vaccine researchers are exceptionally well-acquainted.
Measures that encourage cross-pollination of ideas and techniques often prove helpful, Salmon adds. "As you find in many specialties, in the TB vaccine world there's a relatively small group of players," he says. "We're hoping that by bringing in some different perspectives, people will get some fresh ideas. Maybe we'll even convince more people to come work on TB."
One last aspect the symposium aims to address is the process of site selection. Representatives from a number of high-incidence countries - the Gambia, Brazil, India, Pakistan, and Nigeria - were all expected to discuss advantages and disadvantages offered by their respective countries.
One aspect of site selection is infrastructure - or rather, what to do about it when it's not there, says Salmon. When does it make sense to create more infrastructure on site? When does it work best to ship specimens out of the country?
The NVPO's function is to serve as a quarterback to vaccine researchers, coordinating efforts of such agencies as the National Institutes of Health, the Centers for Disease Control and Prevention, and the Food and Drug Administration, says Salmon.
At press time, conference organizers were expecting a good turnout and had almost 100% acceptance from suitably high-powered invited speakers. "I think people recognize this is something that's very timely and important," says Salmon. "We really need to push forward here. We have high expectations."
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