Vaccination
Vaccination is the simplest, most efficient and cost-effective way to prevent life-threatening infections in the community.
For thousands of years man has known that recovery from some diseases, which we now know to be infections, leads to freedom from the same disease again, often for life. This is called immunity.
Edward Jenner made the first rational approach to vaccination using a closely related virus - cowpox - to protect people against the ravages of the smallpox virus. His work was the first controlled clinical trial of a treatment to prevent disease in man.
How Does Vaccination Work?
Vaccination relies on the ability of the immune system to remember past infections and store products from that immune response in case of a future infection by the same disease.
Vaccination copies, in a more directed and controlled way, the process of infection and immune response triggered by a foreign invader. When you are vaccinated against a particular disease you are being injected with all or part of that disease-causing organism. Your body mounts an immune reaction, producing specific antibodies. These then remain in your system to be activated in the event of a future attack.
Vaccine induced immunity works in four ways:
1. Antibodies in the gut and airways, the most likely sites of infection, bind onto the disease-causing bacteria or viruses, preventing them from latching on to and penetrating the cells lining these passages.
2. Antibodies in the airways, gut and tissues bind with and neutralise the poisons released by some disease-causing bacteria. This happens with the diphtheria toxin in the throat and tetanus toxin in the body tissues.
3. Immune cells, called cytotoxic T cells, kill virus-infected cells. Measles vaccine stimulates this response.
4. Another kind of T cell helps other body cells to kill bacteria that have got inside them. They do this by releasing messenger molecules which act on the infected cells and cause inflammation. The BCG vaccine against tuberculosis (TB) does this.
What are Vaccines made of?
Immunisation is described as active or passive.
In active immunisation part or all of the disease-causing organism which has been modified in some way is inserted into your body, causing it to set up an immune response, produce cells and antibodies to kill the disease and store protective cells in case of future infection. This uses:
Live vaccines
1. Non-harmful organisms closely related to the disease-causing bacterium or virus, for example smallpox and cowpox.
2. The disease-causing bacterium or virus itself that has its disease inducing properties removed. These are known as attenuated vaccines. This form of vaccine is used against measles, mumps, rubella and tuberculosis.
Inactivated vaccines
1. The toxins (poisons) produced by disease-causing bacteria, modified to make them harmless. The current vaccines against diphtheria and tetanus use this method.
2. The dead disease-causing agent. Whooping cough, rabies and anthrax vaccines are examples of these.
3. Genetically engineered or purified molecules from the disease causing organism. These are used against pneumonococal bacteria.
In passive immunisation the antibody products of an immune response harvested either from a person who is recovering from the disease or made specifically for use in immunisation, are injected into the body.
The BCG vaccine against Tuberculosis.
At the beginning of the 20th century two French scientists, Albert Calmette and Camille Guérin cultured the bacterium that causes tuberculosis in cattle over a period of ten years. During this time the culture acquired stable changes that altered the bacterium to a new species called Bacillus Calmette Guérin (BCG). The changes resulted in a much less virulent kind of tuberculosis which when used as a vaccine protects you against the deadly tuberculosis infection.
How Long Does The Effect Of Vaccination Last?
This depends on the type of vaccine. With inactivated vaccines, you need several booster vaccinations to build up a high state of immunity. With live vaccines the effect is more long lasting and one shot in infancy and a booster in old age is generally enough.
Routine Vaccination
Many vaccines have been developed since the time of Edward Jenner. He knew nothing of the scientific basis for vaccination or the identity of the germs that cause disease. It was another 100 years before the French scientist Louis Pasteur introduced vaccines against rabies and anthrax. At about this time too, in Germany, Emil von Behring developed a vaccine for diphtheria from the antibodies produced by patients recovering from the disease.
In the 1980s the World Health Organization (WHO) and the United Nations Children's Fund (UNICEF) launched the "Expanded Programme for Immunisation" - a worldwide programme of child vaccination. It has brought polio vaccination to over 80% of the world's children. The WHO estimates that 3.2 million lives were saved from measles, neo-natal tetanus and whooping cough in 1990.
Childhood Vaccination in the United Kingdom
Today in the United Kingdom parents are encouraged to have their children vaccinated against major infectious diseases such as measles, mumps, rubella, polio, whooping cough, diphtheria, tetanus and cervical cancer. Until the middle of the twentieth century many people caught these diseases, many children died from them or were disabled as a result of them. Other vaccines are recommended during the course of life.
There are occasional scares about the safety of some vaccines. Some people believe vaccines overload our immune system, making it less able to react to other diseases which are now threatening our health such as meningitis, AIDS and cancer. The debate will continue as long as there are statistics to manipulate. A few people are advised against the use of a particular vaccine, but for most "The vaccine is safer than the infection".
Measles
Measles is caused by a virus that attacks many organs in the body. The most visible sign of infection is a red rash on the skin. It can leave you blind or brain damaged or even result in death. Measles vaccine has been widely used since 1964.
Mumps
Mumps is caused by a virus that infects the salivary glands, resulting in swelling of the neck. Complications can set in if the infection moves to the brain. If a mother catches the disease in the first three months of pregnancy her baby may be born with abnormalities. A vaccine came into general use in 1967.
German measles
German measles (rubella) is a minor viral infection, but can be serious if a woman catches it when she is pregnant. Her baby may be born with abnormalities. Vaccination for this disease was introduced in 1970.
Polio
Polio is caused by a virus that attacks the ends of nerves resulting in various degrees of paralysis in its victims. Vaccination has been available since 1953.
Diphtheria
Diphtheria is a severe bacterial infection of the tonsils. The tonsils swell and block the airways, causing the victim to suffocate. Blood poisoning also occurs. Vaccination became widespread in 1942.
Whooping cough
Whooping cough is a bacterial disease that produces a persistent cough. The victim may go into spasm and suffer from encephalitis (swelling of the brain) which may result in permanent brain damage. Vaccination was introduced in 1957.
Tetanus
Tetanus is caused by a bacterium that lives in the soil. It produces a poison that attacks the central nervous system resulting in spasms and paralysis, commonly known as lockjaw. The victim's bodily functions seize up and their bodies waste away. Vaccination has been available since 1914.
New Horizons
The problem does not stop with the main diseases of childhood. WHO estimates that another 14 million people a year die of other major infections such as malaria, hepatitis, meningitis, those that cause diarrhoea and respiratory diseases, tuberculosis and HIV.
"The development of new vaccines to combat these diseases presents a great challenge. Vaccines have already been developed that are being used to treat conditions such as cancer".
© 2009 Edward Jenner Museum
Registered Charity 284085
Berkeley, Gloucestershire, England.
