Dead or inactive forms of a pathogen are used to make a vaccine. Vaccines can be injected into the body. The process is called vaccination (immunisation).
The white blood cells react by producing antibodies, as they would if you were infected by a live pathogen.
This response makes the person immune. It prevents subsequent infection because if the body meets this pathogen, it responds quickly by producing more antibodies.
Specific antibodies recognise a particular antigen (usually a protein shape) on the pathogen.
The MMR vaccine prevents measles, mumps and rubella. It is one of several vaccines given to children and young people, to protect them and the population.
Most people in a population need to be vaccinated to protect society from very serious diseases. This is known as herd immunity.
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Antibiotics and painkillers
Painkillers and some other medicines treat the symptoms of disease, but do not kill the pathogens that cause it.
Antibiotics cure bacterial disease by killing the bacterial pathogens inside your body.
Antibiotics kill infective bacteria in the body. They destroy the bacteria without damaging the body cells. Antibiotics cannot be used to treat viral diseases.
Viruses are difficult to kill because they reproduce inside the body cells, so any treatment for viral infections could also damage the body cells.
Your immune system will usually overcome the viral pathogens.
Strains of bacteria have evolved that are resistant to some or all of the available antibiotics. This means the antibiotics cannot kill the bacteria and the disease cannot be cured.
Scientists need to find new drugs to kill the antibiotic-resistant bacteria.
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Discovering drugs
Many drugs still used today were extracted from plants or microorganisms.
Penicilllin is an antibiotic that was found in the mould Penicillium. It was discovered by Alexander Fleming but developed by other scientists as an antibiotic.
Scientists in the pharmaceutical industry often use chemicals extracted from plants or fungi to develop new drugs.
Digitalis and digoxin are drugs extracted from the foxglove plant. Digoxin is still used to strengthen the heartbeat, alongside more modern drugs. Asprin was first prepared from a compound found in the bark of a willow tree. Scientists are hoping that microorganisms in the soil might reveal new antibiotics to kill antibiotic-resistand bacteria.
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Developing Drugs
Scientists test large numbers of substances to see if they might cure a disease or relieve symptoms.
Researchers test new drugs to make sure they are effective, safe, stable, and can be taken into the body and removed easily.
Preclinical testing is carried out in laboratories on cells and tissues or organs. If the drug seems to work it is then tested on animals.
Clinical trials then take place on healthy human volunteers and finally on patients.
Healthy people are given very low doses of the drug to find out if it is safe.
In some trials with patients, a placebo is used. A placebo does not contain a drug. Some patients have the drug, others are given the placebo. This is to check that the drug being tested really does have an effect on the patient.
In a double-blind trial, neither the doctor nor the patient knows who is given a drug and who is given a placebo.
People taking part in a drug trial are asked to report any side effects.
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