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.
1 Muscle tightness can also cause neck pain. Gently stretch your neck to ease the tension in the neck muscles. Exercise the weak neck muscles to improve the blood flow in this area and relieve pain.  Sternocleidomastoid (SCM) Exercise - The SCM is the large muscle at each side of the neck that causes much pain.