Prevention you can count on: Progress toward developing vaccines for HIV, TB and Malaria

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This post is by Center Director Christine Lubinski.

Researchers outlined progress and challenges in the pursuit of vaccines for the three major infectious disease killers—HIV , tuberculosis and malaria—at a congressional briefing on Capitol Hill Monday. Dr. Hoosen Coovadia, from the University of KwaZulu-Natal in Durban, South Africa, set the tone for this collaborative briefing, entitled “New Promise in the Search for HIV, TB and Malaria Vaccines,” by noting that from his perspective as a South African physician, vaccines for these three deadly diseases were not conflicting priorities, but all critical to protect the citizens of his country.  “One can’t choose what people will die from,” he said.

Drs. Alan Bernstein, executive director of the Global HIV Vaccine Enterprise, and Dan Barouch, chief of the Division of Vaccine Research at Beth Israel Deaconess Medical Center, highlighted the ups and downs of HIV vaccine development by noting that only 3 HIV vaccine concepts have been tested in the last quarter century. But they also celebrated the latest results of the so- called Thai trials, which demonstrated a 31percent reduction in HIV acquisition for those who received the vaccine compared to placebo.  While this level of protection is too low to bring a product to market, it does suggest that a preventive vaccine is indeed possible, and these findings offer an unprecedented opportunity to explore and investigate the nature of that protection.

Dr. Gordon Douglas, executive chair of the Aeras Global TB Vaccine Foundation, called tuberculosis the most neglected of all infectious diseases and joked he was “even amazed that we are on the program.”  Eight years ago, when Aeras started, there were no TB vaccine candidates in clinical development. Since then, nine candidates have been brought forward.  Dr. Coovadia, a member of the Aeras board, outlined a number of urgent reasons to develop a TB vaccine, including the scale of morbidity and mortality from TB, growing drug resistance, the deadly synergy between HIV and TB and the very limited effectiveness of the BCG vaccine. The BCG vaccine only prevents disseminated tuberculosis in very young children; it has no impact on pulmonary tuberculosis in children or adults.  AERAS has two promising TB vaccine candidates in Phase IIB clinical trials in the developing world and hopes to have results in 6-7 years.  In pressing forward on vaccine development, AERAS has been mindful of the issue of access to the vaccine every step of the way and has not considered candidates that would be too costly to manufacture for mass distribution.

Colonel Chris Ockenhouse, director of the U.S. Military Malaria Vaccine Program, and Dr. Ashley Birkett, from the PATH Malaria Vaccine Initiative, briefed the audience about progress towards developing a malaria vaccine.  The US military has been working in the field of malaria for decades, given the infection risk to US troops deployed in many parts of the world. 

Over 40 percent of the world’s population is at risk for malaria, and it causes almost one million deaths a year—primarily in children under the age of five.  With resistance to anti-malarial drugs and to insecticides a constant problem, a malaria vaccine is clearly the missing tool in the battle to eradicate malaria.

The hurdles are significant.  Just as with tuberculosis, there is no major commercial market for a malaria vaccine, and there is not currently a vaccine in use that protects against a parasite.  Nevertheless, progress in malaria vaccine development has been significant since there is now a vaccine candidate that is 50 percent effective. Researchers are continuing to test vaccine candidates, hoping to increase the effectiveness of a malaria vaccine to 80 percent.

Malaria vaccinologists have an advantage over those working in HIV and TB vaccine development because they are able to test potential vaccine candidates in the U.S. with small numbers of people.  This process allows scientists to immunize subjects with the vaccine candidate, challenge the vaccine by injecting the patient with the parasite, monitor the response, and then treat them with anti-malarial drugs if they begin to show symptoms of malaria.

James Kublin, director of the HIV Vaccine Trials Network, closed the briefing by highlighting the terrible burden of the three infectious disease killers and the synergy that exists among the three.  He noted, in particular, the impact of HIV on the size of the labor force and the GDP in countries of high prevalence.  The take-home message was that although vaccine development is expensive, it is far cheaper than treating these diseases or in dealing with the financial consequences to the community and the nation at large He also outlined a strategy—so-called adaptive clinical trials that would allow vaccine candidates to be evaluated more quickly and cheaply by evaluating them as early as possible for ineffectiveness.

During the Q & A session, there was also a broader discussion of the benefits of conducting research, including vaccine trials , in developing countries, including training for developing country researchers, and enhanced clinical and laboratory infrastructure.

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