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.
There are many causes of tight neck muscles. The causes of tight neck muscles are many: poor posture, emotional or mental stress, asymmetric use of the neck, back, or arms at work or at play, injury to any of these areas, carrying a heavy bag primarily over one shoulder, or across the chest, and so forth.