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August 20, 1998
Contact: CDC, National Center
for HIV, STD and TB Prevention
Office of Communication
(404) 6398895

Update: Development of New Vaccines for Tuberculosis

Recommendations of the
Advisory Council for the Elimination of Tuberculosis Releases

The federal Advisory Council for the Elimination of Tuberculosis (ACET) has published new recommendations for the development of tuberculosis vaccines in a special August 21, 1998 issue of the Morbidity and Mortality Weekly Reports. The recommendations call for a national initiative to address the critical need for a new vaccine for tuberculosis. TB is an airborne, potentially fatal, lung disease that now kills more people worldwide each year than any other infectious disease.

Time for the Next Major Step in TB Elimination: A Vaccine is Needed

During the past decade, the United States and several other countries have embarked on plans to eliminate TB. In 1989, CDC published the Strategic Plan for the Elimination of Tuberculosis in the United States. The plan was published during a U.S. resurgence of the disease, at a time when the nation had let its guard down. In the mid-80's, the U.S. was well on its way to TB elimination, but in 1985, after redirecting TB prevention and control resources to other areas, the country witnessed a reversal in declining trends. Between 1985 and 1992, TB cases increased by 20 percent and outbreaks of multi-drug resistant TB resulted in high death rates.

Since that time, the U.S. has rebuilt its systems for combating TB and has successfully brought the disease back under control. Current strategies have reduced the number of active cases of disease in the U.S., and the expanded use of directly observed therapy (DOT) has helped decrease the number of drug-resistant cases. Yet, the rate of TB remains nearly 75 times higher than the level necessary to eliminate this disease as a U.S. public health threat.

ACET concludes that "better application of current diagnostic, treatment, and prevention strategies could lead to gradual decreases in this disease, but eliminating TB completely in the United States and internationally will require new tools." The ACET recommendations outline the next steps for developing the tool that could have the greatest impact - an effective vaccine for tuberculosis.

Limitations of Existing Tools

TB elimination efforts are currently two-pronged. First, to prevent severe illness, death, and transmission of disease, people with active cases of tuberculosis must be properly diagnosed and treated. TB disease can almost always be cured with existing medications, but the 6 month treatment regimen must be taken exactly as prescribed, or drug-resistance can develop. Second, there are an estimated 15 million Americans infected with the TB bacteria who are at risk of developing active TB disease in the future.

Reaching those at highest risk for developing active disease with preventive therapy is the second priority of TB elimination efforts. This includes reaching recent contacts of infectious patients, HIV-infected populations, and individuals born in areas of the world where TB is common. While these approaches are currently allowing the U.S. to keep TB in check, alone they cannot eliminate this threat:

 

  • The most effective strategy for treating active disease, DOT, has helped reduce drug-resistance and disease spread in the U.S. And the widespread application of the World Health Organization's Directly Observed Therapy Short-Course (DOTS) strategy remains the most effective means for TB control globally. However, this strategy requires complex systems that may be difficult to maintain in low-income areas. Continued support will be needed to maximize the impact of this strategy.
  • Preventive therapy for people at highest risk for developing TB disease is also an important strategy. However, simpler regimens and improved screening strategies are needed to improve the effectiveness of this strategy. Adherence and drug toxicity remain problems for many.
  • The only existing vaccine, the bacille Calmette-Guerin (BCG) vaccine, has had little impact on the spread of TB. Although it has prevented TB deaths in children, the largest and most recent trial of BCG found the vaccine to have no overall protective effect against TB infection and disease in adults. Further, the vaccine can complicate TB screening by producing a false-positive test result in people not actually infected with the TB bacteria. Because of its beneficial effects in protecting against some serious forms of childhood TB (i.e., TB meningitis and disseminated miliary TB) and leprosy, BCG vaccine will likely remain a component of childhood vaccination strategies in developing nations. Other than in exceptional situations, BCG has never been recommended for use in the U.S.

In addition to more effectively using preventive and curative treatment, TB elimination requires the development of a more effective vaccine.

Post-infection Vaccine Offers the Best Hope for Elimination

ACET recommends that new efforts include focusing on a "post-infection vaccine", rather than exclusively on the traditional approach to vaccine development. To eliminate TB, it is critical to develop a vaccine that not only prevents new infection, but that will effectively prevent the millions of people infected with TB from developing active TB disease. A post- infection vaccine could be the most important new tool to eliminate TB in the United States and across the globe. Approximately one-third of the world's population is already infected with the TB bacteria.

Recent scientific advances have provided an unprecedented opportunity to move forward with TB vaccine development. Genome sequencing has provided a new understanding of the makeup and functioning of the TB bacteria, and advances in genetic and molecular technology allow approaches never before possible.

ACET is recommending that public agencies and vaccine manufactures make TB vaccine development a priority; commit to ongoing support; develop a comprehensive strategic plan beginning with the recently developed NIH Blueprint for TB Vaccine Development; establish the collaborations needed to implement clinical vaccine trials; increase basic research; and develop a clear consensus on the desirable characteristics of a new vaccine. The National Vaccine Program Office will hold an international symposium August 26-28, 1998 in San Francisco, CA, which may serve as an important first step to responding to these recommendations and moving forward with the next step toward TB elimination.

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