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• Antibiotics are medicines which kill bacterial infections.
• Vaccines protect us against viral infections.

Drugs are substances that have an effect on the body. Medicines, like antibiotics, are drugs that help treat people suffering from pain or disease. Not all drugs are medicines.

Antibiotics only treat bacterial infections, including those shown in the table.

Different antibiotics work in different ways:

• Some kill bacteria by breaking down their outside layer.
• Some stop bacteria from reproducing so they can't spread.
• Some can stop the chemical processes happening inside bacteria.

Antibiotics have saved millions of lives and continue to do so today. Their discovery changed the world of medicine.

Antibiotics have no effect on viral infections like the common cold or flu.

Sir Alexander Fleming (1881-1955) was a Scottish scientist who discovered the antibiotic; penicillin.

In 1928 Fleming was working on bacteria which he grew on agar plates. He returned to work from a holiday and noticed that one of the plates was infected with a fungus. He noticed that the bacteria did not grow near the fungus. He then found that the fungus naturally produced a substance to defend itself against bacterial infection. He isolated this and named it penicillin after the fungus.

He won the Nobel Prize for this achievement.

After his discovery, Fleming noticed that bacteria were more likely to survive if too little penicillin was used or it was used for only a short period. This antibiotic-resistance occurs because bacteria, like all life, are evolving.

Scientists are working on developing new antibiotics, but it is a long and expensive process. Immediately after each new antibiotic is discovered, there is very little resistance. But as the new antibiotic is widely used, bacteria have more opportunities to evolve and develop resistance. Not all bacteria are killed if antibiotics are prescribed in a dose that is too low or for not long enough.

Some scientists are worried that the evolution of antibiotic resistance is happening faster than we are able to discover new antibiotics. This could mean that bacterial infections that are easy to cure now might be untreatable in the future.

Vaccines are medicines which mainly prevent viral infections. Giving someone a vaccine is called vaccination. Vaccines have been developed for many viral infections.

Some vaccines are effective against bacterial infections such as typhoid but most work against viruses.

Unlike antibiotics treating bacterial infections, vaccines do not actually kill the viral infection. Vaccines are given before infection to protect the person.

Vaccines are often ‘dead’ or weakened versions of the virus. Some more recent vaccines are small sections of the virus's genetic information (RNA or DNA). Vaccines do not infect the person receiving them with the illness, but do cause an immune response when given. This can make some people a little ill shortly after vaccination, but these symptoms are almost always much less severe than the infection itself.

The immune response causes the vaccinated person’s white blood cells to produce specific antibodies which fight the infection. If the person then catches the virus, their white blood cells can make these antibodies faster and often stop them becoming severely ill. At this point, a vaccinated person now has increased immunity to infection.

Natural immunity is when a person gets the infection and manages to fight it without a vaccine. The symptoms for chickenpox are generally mild and so the vaccine is only given in the UK to those people with less effective immune systems. Most people have natural immunity from chickenpox as they had the illness as a child.

Scientists, doctors and nurses overwhelmingly agree that vaccination is a vital way of protecting from infection.

English scientist Edward Jenner (1749-1823) carried out important research into early vaccines. He is called the ‘father of immunology’ and his work is thought to have saved countless lives. Smallpox is a deadly disease that was common during Jenner’s lifetime. It killed between 10 and 20% of the population.

Jenner observed that people who milked cows were generally immune to smallpox. These workers caught cowpox from cows, and this gave them blisters. Jenner suggested that the pus in the cowpox blisters protected them from smallpox. Cowpox is similar to smallpox but causes fewer deaths.

In 1798 Jenner tested his hypothesis by injecting an eight-year-old boy with the pus from cowpox. The boy fell ill but recovered. The boy was then immune to infection from smallpox. It took nearly two hundred years, but in 1980 the World Health Organisation declared smallpox to be eradicated.