From birth, we are constantly exposed to many different viruses, bacteria and other microbes. Most are not harmful, many are beneficial but some can cause disease.
The body's immune system helps protect us against infections. When we are exposed to infection, the immune system triggers a series of responses to neutralise the microbes and limit their harmful effects. Exposure to an infectious disease often gives lifelong protection (immunity) so we do not contract the same disease again. Our immune system “remembers” the microbe.
Simple and effective protection
We often develop lifelong immunity when we have had a disease. However, some diseases may lead to serious complications and sometimes death. The aim of vaccination is to obtain this immunity without any of the risks of having the disease.
When we vaccinate, the immune system's "memory" is activated. During vaccination, a weakened microbe, a fragment, or something that resembles it, is added to the body. The immune system is then activated without us becoming sick. Some dangerous infectious diseases can be prevented in a simple and effective way. For some diseases, vaccination will lead to lifelong protection, while for others the effect is diminished after a few years and booster doses are required.
Infants tolerate vaccines well
Our immune system is already prepared early in the womb to tackle various microbes that we encounter after birth. Vaccines use only a small part of a child's immune capacity and burden the immune system to a much lesser degree than common infections, such as a cold. Infants therefore tolerate vaccination well, including receiving several vaccinations at once.
When the majority of the population has been vaccinated against a disease, there will be few people left to whom the infection can spread. This protects the few who have not been vaccinated.
With the help of vaccination, it is possible to entirely eradicate some diseases worldwide. So far, this has been achieved for smallpox.
Childhood Immunisation Programme
In Norway, all vaccination is voluntary.
The recommended vaccination programme for children and adolescents includes vaccines against twelve different diseases: rotavirus, diphtheria, tetanus, whooping cough, poliomyelitis, infection with Haemophilus influenzae type b (Hib), hepatitis B, pneumococcal disease, measles, mumps, rubella and human papilloma virus (HPV), which can cause cervical cancer and other cancers cause by HPV. Some children are also offered vaccination against tuberculosis. All these diseases can be life-threatening or result in serious complications.
Vaccination usually begins when a child is six weeks old. Since several of the diseases vaccinated against affect the youngest children the hardest, delays should be avoided. Booster doses are given when a child reaches school age.
How are vaccines given?
The rotavirus vaccine is given orally (drinkable vaccine). The other vaccines are administered by injection. Mercury is not used as a preservative in any of the vaccines in the Childhood Immunisation Programme.
Combination vaccines have been used since the Norwegian Childhood Immunisation Programme began in 1952. These contain vaccines against several diseases in the same syringe, which means fewer injections for the child. The combination vaccines result in fewer side effects than when the vaccines are given individually.
What happens in the body when we vaccinate?
During vaccination, the body is exposed to either a weakened microbe (bacteria or virus), fragments of a microbe, or something that resembles the microbe. When the active substances in the vaccine meet the body's immune system, immune cells and antibodies are produced that will recognise the "real" microbe. When the vaccinated person encounters this microbe, the immune system will provide a faster and better immune response that can prevent disease. This is artificially acquired active immunity.
A good vaccine will provide adequate and prolonged protection against the disease. The number of doses needed varies from vaccine to vaccine. For some vaccines, there is a need for a booster dose later in life to maintain protection. These include vaccines against tetanus, diphtheria, polio and pertussis. Booster doses may also be required for travel vaccines.
What is immunity?
When the body is infected with a microbe (virus, bacterium, parasite or fungus), it stimulates the production of important immune cells. After recovery from a disease, some of the immune cells will "remember" the microbes that the body was infected with. This is called immunological memory. Next time the body is exposed to the same type of microbe, the immune system will recognise it. The body's defence against the disease becomes faster and more powerful and can prevent the person from becoming ill. This is naturally acquired active immunity.