In the last centuries several infectious diseases have been combated by vaccination techniques, e.g. small pox infections. Routine immunization of healthy infants, children and adults play a major role in preventing the outbreak of several serious infectious diseases such as German measles, mumps, pertussis, tetanus, diphtheria, hepatitis B and others. Unfortunately, vaccination and immunization are not always available as a form of protection against many frequently acquired infections.

Any condition that weakens or interferes with a person’s immune defenses or overall physical condition increases the susceptibility to infection. People with an impaired immune system are extremely vulnerable. The elderly and the very young are especially prone to infections because immune functions decline with aging and are not yet fully developed in children.

The immune system can be impaired by infections (e. g. HIV), anti-cancer therapy, organ transplants or chronic diseases such as diabetes or rheumatoid arthritis. Certain lifestyle measures such as nutritional deficiencies, smoking and alcohol abuse can also lead to diminished host defenses. All injuries, including even minor wounds of the intact natural protective skin and mucous membrane barriers, facilitate the invasion of possible pathogens.

Therefore, precautionary measures should include participating in routine immunizations, amplifying natural immune responses by beneficial life style changes and hygienic measures to prevent transmission. Especially people with impaired immune functions should be aware of transmission modes and thus avoid direct contact with infected people.