Vaccine Science
What is a Vaccine?
Vaccines are critically important to public health. Since the first smallpox vaccine was introduced in the late 18th century by Edward Jenner, an English country doctor, vaccines have saved the lives of millions of people around the world.
Vaccines work by stimulating the body's immune system to recognize and fight off the disease-causing agents. In most cases, weakened or killed microorganisms are injected into the body. This causes the immune system to develop antibodies to those organisms without the person ever becoming sick. When the immunized person encounters live or full-strength microorganisms later on, their body's immune system is able to immediately recognize the threat and make the appropriate antibodies, thereby preventing illness. Vaccines have been created for many once-deadly diseases, including polio, mumps, measles and smallpox. |
TB VaccineA vaccine against tuberculosis, the Bacille Calmette-Guérin (BCG) vaccine, has existed since 1921. Unfortunately, its efficacy is highly variable and in some trials has been shown to be disappointingly low. Though the BCG vaccine, developed from a strain of TB affecting cattle, is the most widely distributed vaccine in the world, administered to over 100 million babies annually, TB still kills over 1.7 million people every year.The high rate of TB in developing countries has been exacerbated by many causes, including the HIV/AIDS pandemic, war, political instability, drug resistance and poverty. Therefore, one of the highest priorities of TB research is to develop one or several more effective vaccines. Next-Generation TB VaccinesIn recent years, a number of new vaccine candidates for TB have been developed and shown promising results when tested in animals. Some of the new vaccine candidates are beginning to enter human safety trials. This is real progress for the field of TB vaccine development. Aeras is among the world leaders in the development of new TB vaccines, and its pipeline of candidates is an excellent example of the variety of strategies researchers from all over the world are using to develop new TB vaccines. The Aeras pipeline includes recombinant BCG vaccines, new recombinant fusion proteins given with new adjuvants, and non-replicating or replication-deficient viral-vectored vaccines. Other researchers have developed vaccines based on weakened Mycobacterium tuberculosis (M.tb) itself, instead of the weakened Mycobacterium bovis used in BCG.Many of these vaccines are designed to over-express certain TB antigens that are recognized by the immune system, thereby further preparing the body's defenses for exposure to the actual microbe that causes TB. Others function to prevent the germ from hiding in cells, a strategy which allows it to hide from the body's immune system. New TB vaccines to prevent childhood and adult forms of TB, to prevent progression of latent TB infection to the active disease stage, and to shorten drug treatment regimens or reduce the risk of relapse, can all fundamentally alter our approach to TB control. Prime-Boost StrategyThe new generation of TB vaccines will probably work best via a strategy called "prime boosting." An initial vaccine, either the existing BCG vaccine or one made, for example, from a new recombinant BCG (rBCG), would be administered. This "prime" inoculation would be followed by a "booster" shot. For example, infants and young children who have never been exposed to TB might get a shot of a different vaccine. There could be a separate booster for young adults, or the booster shot might be used to treat the disease itself as an adjunct to treatment with TB drugs.Researchers believe this "prime-boost" strategy will not only enhance protection, but also extend protection over a longer period of time. This is a critical concern when you consider that the highest level of TB infection is among young adults. TB vaccines under development could:
Priming, Pre-Exposure: Vaccine candidates that would serve as the "prime" in a prime-boost regimen and be intended to prevent TB in people who have not been infected with M.tb. Boosting, Pre-Exposure: Vaccine candidates that would serve as the "boost" in a prime-boost regimen and that are intended to prevent TB in people who have not been infected with M.tb. Post Exposure — Immunotherapy: Vaccines candidates that could be administered after a person has been exposed to M.tb to prevent reactivation or progression to the disease stage and shorten or improve response to chemotherapy > click to view our portfolio of vaccine candidates > click to download the Stop TB Partnership's TB Vaccine's Pipeline (.pdf - 672kb) |