| TB prevention and control takes two parallel | | | | in phase III trials is MVA85A, which is being trialed in |
| approaches. In the first, people with TB and their | | | | South Africa by a group led by Oxford University, |
| contacts are identified and then treated. Identification | | | | and is based on a genetically modified vaccinia virus. |
| of infections often involves testing high-risk groups | | | | Because of the limitations of current vaccines, |
| for TB. In the second approach, children are | | | | researchers and policymakers are promoting new |
| vaccinated to protect them from TB. Unfortunately, | | | | economic models of vaccine development including |
| no vaccine is available that provides reliable protection | | | | prizes, tax incentives and advance market |
| for adults. However, in tropical areas where the | | | | commitments. |
| incidence of atypical mycobacteria is high, exposure | | | | Epidemiology |
| to nontuberculous mycobacteria gives some | | | | According to the World Health Organization (WHO), |
| protection against TB. | | | | nearly 2 billion |
| Vaccines | | | | “third of the world's |
| Many countries use BCG vaccine as part of their TB | | | | ¢â€šÂ¬Ã¯Â¿Â¾have tuberculosis. Annually, 8 |
| control programs, especially for infants. This was the | | | | million people become ill with tuberculosis, and 2 million |
| first vaccine for TB and developed at the Pasteur | | | | people die from the disease worldwide. In 2004, |
| Institute in France between 1905 and 1921. However, | | | | around 14.6 million people had active TB disease with |
| mass vaccination with BCG did not start until after | | | | 9 million new cases. The annual incidence rate varies |
| World War II. The protective efficacy of BCG for | | | | from 356 per 100,000 in Africa to 41 per 100,000 in |
| preventing serious forms of TB (e.g. meningitis) in | | | | the Americas. Tuberculosis is the world's greatest |
| children is greater than 80%; its protective efficacy | | | | infectious killer of women of reproductive age and |
| for preventing pulmonary TB in adolescents and | | | | the leading cause of death among people with HIV |
| adults is variable, ranging from from 0 to 80%. | | | | AIDS. |
| In South Africa, the country with the highest | | | | In 2004, the country with the highest incidence of |
| prevelance of TB, BCG is given to all children under | | | | TB was South Africa, with 718 cases per 100,000 |
| the age of three. However, the effectiveness of | | | | people. India has the largest number of infections, |
| BCG is lower in areas where mycobacteria are less | | | | with over 1.8 million cases. In developed countries, |
| prevalent, therefore BCG is not given to the entire | | | | tuberculosis is less common and is mainly an urban |
| population in these countries. In the USA, for | | | | disease. In the United Kingdom, TB incidences range |
| example, BCG vaccine is not recommended except | | | | from 40 per 100,000 in London to less than 5 per |
| for people who meet specific criteria: | | | | 100,000 in the rural South West of England. the |
| Infants or children with negative skin-test result who | | | | national average is 13 per 100,000. The highest rates |
| are continually exposed to untreated or ineffectively | | | | in Western Europe are in Portugal (42 per 100,000) |
| treated patients or will be continually exposed to | | | | and Spain (20 per 100,000). These rates compare |
| multidrug-resistant TB. | | | | with 113 per 100,000 in China and 64 per 100,000 in |
| Healthcare workers considered on an individual basis | | | | Brazil. In the United States, the overall tuberculosis |
| in settings in which high percentage of MDR-TB | | | | case rate was 4.9 per 100,000 persons in 2004. |
| patients has been found, transmission of MDR-TB is | | | | The incidence of TB varies with age. In Africa, TB |
| likely, and TB control precautions have been | | | | primarily affects adolescents and young adults. |
| implemented and not successful. | | | | However, in countries where TB has gone from high |
| Several new vaccines to prevent TB infection are | | | | to low incidence, such as America, TB is mainly a |
| being developed. The first recombinant tuberculosis | | | | disease of older people. |
| vaccine entered clinical trials in the United States in | | | | There are a number of known factors that make |
| 2004, sponsored by the National Institute of Allergy | | | | people more susceptible to TB infection: worldwide |
| and Infectious Diseases (NIAID). A 2005 study | | | | the most important of these is HIV. Co-infection with |
| showed that a DNA TB vaccine given with | | | | HIV is a particular problem in Sub-Saharan Africa, due |
| conventional chemotherapy can accelerate the | | | | to the high incidence of HIV in these countries. |
| disappearance of bacteria as well as protect against | | | | Smoking more than 20 cigarettes a day also |
| re-infection in mice; it may take four to five years to | | | | increases the risk of TB by two- to four-times. |
| be available in humans. The only TB vaccine currently | | | | |