Effectiveness

• Vaccines protect the recipient and the people in close contact with him or her. When a person does not get infected with a disease, he or she will also not pass it on to others. This way even those who are unvaccinated, such as children with cancer, are spared from the disease. This is known as herd immunity.
• The more contagious the disease is, the larger the population vaccination rate needs to be.
• If a vaccinated person is infected by a disease in spite of being previously vaccinated against it, the illness is usually less severe than it would be for an unvaccinated person. The risk of complications and serious sequelae is also reduced.
• Almost all vaccinations require multiple doses to achieve the desired level of immunity. It is important to get all of the doses in a vaccination protocol to achieve long-term, or even lifelong, protection against the disease in question.
• Some vaccines require boosters at regular intervals. These include the diphtheria-tetanus vaccine and the tick-borne encephalitis vaccine, for example. Influenza vaccines must be administered annually because influenza viruses evolve quickly and the previous year’s vaccine is unlikely to provide protection against the new strains.
• Vaccinations have achieved the worldwide eradication of smallpox, which is a very dangerous disease.  The last case of smallpox was in 1977. The WHO is also trying to eradicate polio. One form of polio has already been eradicated from certain parts of the world.
• The National Immunisation Programme in Finland has reduced the prevalence of the MMR diseases, or measles, rubella and mumps, to only a few cases per year. Before immunisation, they afflicted thousands of people each year. Other diseases that are preventable by immunisation have also been similarly reduced by vaccinations.

Further reading

• THL: Children's vaccination coverage (in Finnish)
• THL: Vaccination coverage
• THL: Children's vaccination coverage