Populationsimmunitet

Populationsimmunitet, also known as herd immunity, is a form of indirect protection from infectious disease that occurs when a sufficient percentage of a population has become immune to an infection, whether through vaccination or previous infections, thereby reducing the likelihood of infection for individuals who lack immunity. When a high proportion of the population is immune, it becomes difficult for a disease to spread from person to person, effectively protecting those who are not immune, such as newborns, the elderly, and individuals with weakened immune systems.

The threshold for achieving herd immunity varies depending on the specific disease and its mode of transmission. Highly contagious diseases require a higher percentage of immune individuals to achieve herd immunity compared to less contagious ones. For instance, measles, which is extremely contagious, requires around 95% of the population to be immune to achieve herd immunity.

Vaccination is the most common and effective way to achieve populationsimmunitet. By safely introducing a weakened or inactive form of a pathogen, or a component of it, vaccines stimulate the immune system to develop protection without causing the disease. When a significant portion of the population is vaccinated, it creates a protective barrier that limits the spread of the disease, benefiting even those who cannot be vaccinated. Maintaining high vaccination rates is crucial for sustaining herd immunity and preventing outbreaks of vaccine-preventable diseases.