BY TONY WU
With the invention of vaccines, some diseases that haunted much of human history have begun their move toward extinction. Smallpox, one deadly infectious disease, has been eradicated worldwide. Tetanus, which has nearly been completely eliminated in India, is another disease that is now plaguing fewer people than it has in the past.
Tetanus is caused by the bacteria Clostridium tetani, which is found in soil and manure. Because the tetanus-causing bacteria exists in soil around the world, it can never be truly eradicated. Once the bacteria penetrates the body through small wounds, it starts to produce a toxin that causes muscle spasms, which may be so intense that bone fractures occur.
India first started its vaccination program for tetanus 15 years ago. In India, tetanus is a major contributor to deaths among infants and their mothers. In order to reduce mother and infant mortality rates, the Indian government vaccinated millions of mothers against tetanus as part of the Maternal and Neonatal Tetanus Elimination Initiative started by the United Nations (U.N.) in 1999. The program, which was established in 58 nations besides India, focused on keeping mothers and newborns from developing tetanus.
Pregnant and expectant mothers received government subsidies, usually $21, for giving birth in a hospital. For those who chose to give birth at home, the government provided sterilized instruments, sheets and soap in order to reduce the likelihood of tetanus infection from dirty hands and tools.
Through the government program, India managed to reduce its cases of tetanus to less than one out of 1,000 births. The success in India has been a step toward reducing tetanus mortality rates worldwide. In 2000, over 800,000 people died from tetanus worldwide. So far this year less than 50,000 people have died.
Vaccines can be instrumental in reducing the threat posed by tetanus in other countries as well.
Vaccines were first developed by Edward Jenner, an English physician who observed that people became immune to smallpox after they contracted cowpox. This led to the discovery that people could acquire immunity to infectious diseases through exposure to weakened or dead disease-causing microorganisms. Scientists found that, by exposing the immune system to weakened or dead microbes, the body is able to adapt and overcome certain diseases through either antibody responses or cell-mediated immune responses.
Antibody responses are carried out by lymphocytes, a type of white blood cell that secretes antibodies that bind to foreign materials in the blood. These antibodies deactivate the infectious agents, providing protection to the body. Cell-mediated immune responses, a second type of response that vaccines can trigger, rely on lymphocytes called T cells. These cells are phagocytes, which means that they engulf the foreign microbes or infected cells and break them down. In both of these systems, memory B cells and memory T cells remember the body’s responses to the foreign agents and thereby allow the body to respond faster in a future attack.
Currently vaccines come in several major types, the most common types being inactivated and attenuated vaccines. In an inactivated vaccine, the disease-causing organisms are killed through heat, radiation or other methods. These vaccines often require booster shots after a period of time in order to ensure that their recipients maintain immunity. Some well-known examples of such vaccines include those for influenza, rabies and polio. Attenuated vaccines, on the other hand, utilize live microorganisms that have been specially cultivated. Under controlled conditions, these organisms either closely resemble the disease-causing microbes or have their virulent properties disabled. A major advantage of attenuated vaccines is the prolonged immunity that they offer. Attenuated vaccines are used against diseases such as rubella, typhoid and measles.
There are still many debates regarding the safety and potential side-effects of vaccines. For instance, one commonly voiced concern is that vaccines might prompt the development of autism in children. However, according to the Centers for Disease Control and Protection (CDC), vaccines do not cause autism.
Overall, vaccines have enabled many nations to eradicate infectious diseases that historically plagued their citizens.
