Vaccines have changed the course of human history. Before vaccines became widespread various infectious diseases caused countless adults and children to die or become disabled due to their lack of immunity to fight those dreadful infectious diseases. From the 18th century to the present, we have developed a great variety of vaccines to fight against those dreadful infectious diseases, but we still have the question, why does my shoulder hurt after vaccination? Why does it hurt after the injection? Some people will surely say that this question is not knowingly asked, because the injection needle is stuck into the flesh, so it will definitely hurt. It is true that vaccination will definitely hurt, and this is the most common phenomenon, and these pains usually disappear completely within a day or two. Many people feel a vague pain in the outer shoulder muscles as a result of the injection directly into the muscle tissue. This pain will usually go away on its own, you can ice it if it hurts badly, take some anti-inflammatory medicine, rest for a few days, and the symptoms will lessen. But what if the pain still persists? Does it still feel normal? In fact, shoulder pain can become a chronic problem after vaccination, and vaccination-related shoulder dysfunction (SIRVA) is one of the causes. What is SIRVA SIRVA is a dysfunctional shoulder joint pain and limited range of motion that occurs after vaccine injections used for intramuscular injections in the upper arm. Most of this condition is related to incorrect and unregulated injections, where the needle and agent are injected incorrectly into the subacromial bursa, rotator cuff, and glenohumeral joint. (a) A T1 magnetic resonance imaging (MRI) scan of the left shoulder 7 weeks after vaccination showed subacromial and subdeltoid subacromial bursitis, which had been marked with a measuring tool. (b) T2 MRI scan of the left shoulder 7 weeks after vaccination. Here, the fluid-filled bursa is white in color. Since most of the vaccine with used to stimulate the body to produce antibodies, SIRVA stimulates the body’s immune response leading to complications such as chronic bursitis, adhesive capsulitis, rotator cuff tendinopathy, bone marrow edema, and osteonecrosis. How does SIRVA occur SIRVA is related to incorrect and irregular injections. Due to the millions of new crown vaccinations scheduled and the large number of vaccines that need to be injected every day, the huge workload causes staff fatigue and haste, routine procedures are ignored and the risk of inappropriate injections increases. Proper injection The deltoid muscle of the upper arm is the most common site for intramuscular injections. The deltoid muscle should be positioned, on the lateral side of the upper arm, 2 to 3 transverse fingers below the crest of the shoulder. The lateral deltoid is not vascularized and is far from major nerves, such as the axillary and radial nerves. During the injection, both the patient and the vaccinator should be seated with the upper arm fully exposed, which will facilitate control of the needle and avoid excessive angulation or over-penetration. Symptoms of SIRVA When the vaccine is administered incorrectly, the vaccine injection or needle trauma incorrectly enters the shoulder bursa or its surrounding area, causing an immune response leading to inflammation, triggering a range of typical symptoms including: T2-weighted MRI image of the shoulder 8 weeks after vaccination. The lower left arrow indicates cortical irregularity of the humeral head. Upper middle arrow indicates a partial tear of the supraspinatus tendon. Upper right arrow indicates subacromial bursal effusion. Significant chronic shoulder pain after injection Restricted shoulder motion The following four criteria must also be met for a diagnosis of SIRVA: No primary disease causing shoulder pain Pain that occurs within 48 hours of the injection and does not resolve with pain medication. Restriction of movement and pain limited to the shoulder where the injection was given No other disease that can cause shoulder pain How to prevent SIRVA SIRVA is a very rare complication related to vaccination, which is completely preventable. With only one case reported out of the millions of vaccinations given worldwide in 2019 for the new crown vaccine, this complication is not related to the vaccine and, as with all treatment procedures, can be caused by even insignificant and seemingly harmless manipulations. Here are a few steps to ensure that SIRVA does not occur after an injection: Make sure that any vaccine or staff member is trained in its proper handling. Remove your jacket, or wear a garment that exposes your shoulder (do not peel your shirt and pull it down, exposing only the top of your shoulder); lifting your shoulder too high can cause the needle to inadvertently enter your shoulder joint. If shoulder pain persists for several days after the injection, be sure to seek prompt medical attention. Shoulder injections are very safe, and vaccines always work. The role of vaccines in reducing infectious diseases and their complications is quite significant, preventing about six million deaths per year. Contrary to some conspiracy theories, the benefits of vaccination far outweigh these injection risks. However, nothing is absolute, and this includes chronic shoulder pain caused by improper injections by staff, ensuring that staff are properly trained to administer injections and maintain proper vaccination posture. This helps ensure that such complications do not happen to them.