Vaccines can protect both the people who receive them and those with whom they come in contact. Vaccines are responsible for the control of many infectious diseases that were once common around the world, including polio, measles, diphtheria, pertussis (whooping cough), rubella (German measles), mumps, tetanus, and Haemophilus influenzae type b (Hib). Vaccine eradicated smallpox, one of the most devastating diseases in history. Over the years vaccines have prevented countless cases of infectious diseases and saved literally millions of lives.
Vaccine-preventable diseases have a costly impact, resulting in doctor’s visits, hospitalisations, and premature deaths. Sick children can also cause parents to lose time from work.
Uses of vaccines
Vaccines contain the same antigens or parts of antigens that cause diseases, but the antigens in vaccines are either killed or greatly weakened. Vaccine antigens are not strong enough to cause disease but they are strong enough to make the immune system produce antibodies against them. Memory cells prevent re-infection when they encounter that disease again in the future. Through vaccination, children develop immunity without suffering from the actual diseases that vaccines prevent.
Most people use the terms ‘vaccination’ and ‘immunisation’ interchangeably but their meanings are not exactly the same.
• Vaccination means having a vaccine – that is actually getting the injection.
• Immunisation means both receiving a vaccine and becoming immune to a disease, as a result of being vaccinated.
The immune system recognises germs that enter the body as “foreign” invaders, or antigens, and produces protein substances called antibodies to fight them. A normal, healthy immune system can produce millions of these antibodies to defend against thousands of attacks every day, doing it so naturally that people are not even aware it is happening. Antibodies often disappear once they have destroyed the invading antigens, but the cells involved in antibody production remain and become “memory cells.” Memory cells remember the original antigen and then defend against it if the same antigen attempts to re-infect a person, even after many decades. This protection is called immunity.
Immunisation enables the body to better defend itself against diseases caused by certain bacteria or viruses. Immunisation may occur on its own (when people are exposed to bacteria or viruses), or doctors may provide it. When people are immunised against a disease, they do not get the disease or get only a mild form of it.