Naturally acquired active immunity occurs when the person is exposed to a live pathogen, develops the disease, and becomes immune as a result of the primary immune response. Artificially acquired active immunity can be induced by a vaccine, a substance that contains the antigen.
The main cause of neck pain is tension. During periods of intense anxiety, your muscles tense up dramatically. Muscle tension tightens the muscles, especially in the shoulders, back, and neck. The more anxiety you experience, the more your tension may cause significant pain and discomfort. A related issue comes from the mindset of those with anxiety. Many people get muscle tension in their neck during times of stress.
Sitting in a position where the head is held forward of the shoulders, such as reading or computer use, makes the upper back and shoulder muscles constantly work to hold the head up. Tension may build up due to daily stress. This causes tightness to build up in the upper shoulder and neck muscles, and can cause neck muscle strain. In the event of an unexpected sudden twisting movement, a car accident, or unaccustomed repetitive use of the neck, the neck muscles may become sprained or strained.