Important Facts About Vaccines

In the past vaccinations were mainly used to protect the body against infections. However nowadays vaccines have been developed that can also prevent some cancers. For example, the hepatitis B vaccine can reduce the incidences of chronic hepatitis and also reduce liver cancer. The HPV vaccine can prevent the majority of cervical cancers in women.

Vaccine – Basics

How Do Vaccines Protect Children from Diseases?

Every baby is born with a complete immune system composed of cells, glands, organs, and fluids that are in the body to fight off any invading bacteria and viruses. The immune system recognizes germs that enter the body as "foreign" invaders, or antigens, and produces protein substances called antibodies to fight them. A normal, healthy immune system has the ability to produce millions of these antibodies to defend against thousands of attacks every day. The process is so natural and automatic that people are not aware of the whole process. Many antibodies disappear once they have destroyed the invading antigens, but the cells involved in antibody production remain and “remember” the foreign bodies and then become "memory cells." Memory cells remember the antigen and are capable of producing a much faster response when the same antigen attempts to re-infect the person, even after many decades. This protective response is called immunity.

Vaccines contain the same antigens or parts of the antigens that cause diseases, but the antigens in vaccines are either killed (made inactive) or greatly weakened. When they are injected into fatty tissue or muscle, vaccine antigens are not strong enough to produce the symptoms and signs of the disease but are strong enough for the immune system to produce antibodies against them. Thus through vaccinations, children develop their immunity but without suffering from the diseases themselves.

Misconceptions About Vaccination

The immune system is responsible for fighting infection with an army of specialized cells and chemicals – antibodies. Each time when an infectious agent is encountered, the immune system ‘remembers’ it – this is the memory effect. If the immune system comes in contact with that particular infectious agent again, it can produce an immune response much quicker and destroy it often before the person even notices any symptoms of any illness. Vaccines work by introducing dead or weakened versions of disease-causing organisms to the immune system. When the immune system encounters the ‘real’ disease-causing organisms in the future, quick recognition allows a rapid and effective immune response to protect the body.

Vaccines Don’t Reduce Immunity

There are concerns that having vaccinations reduces ones immune response in the future. This is not true because the effect of a vaccine is to induce the “memory effect” so the immune system can produce antibodies or an immune response much more efficiently in the future.

Vaccine Safety

Vaccines are safe and efficient ways to prevent the spread of many infectious diseases. Every vaccine used in Hong Kong has been thoroughly tested for safety and effectiveness. It is passed for use by the Department of Health and many other authorities in the world such as FDA (Food and Drug Administration) in the USA, and the TGA (Therapeutic Goods Administration) in Australia. Vaccines are subjected to ongoing monitoring and evaluation. However, vaccines are like any other medication - they may trigger side effects in a small percentage of people. All patients are generally advised to remain at the clinic for at least 15 minutes after they or their children are immunized. In the majority of cases any side effects are very mild. The most common side effects include local tenderness, mild fever (due to the body producing an immune response), and mild generalized aches and pains.

Vaccination Schedules

Different countries have different vaccination schedules due to the different risks of disease in their specific locality. To view some of the major countries’ vaccination schedules , please click on the links below.