When to see your doctor, if your post-flu shot shoulder pain doesn’t let up. Right out of the gate, it needs to be said that getting the flu shot is never a bad idea. Versions of the vaccine have been around for more than 70 years, according to the Centers for Disease Control and Prevention —and this year alone, flu vaccine manufacturers expect to supply up to million doses of the vaccine. Basically, the flu shot is safe, reliable, and its benefits greatly outweigh any small risks that may be associated with the vaccine. Typically, those are just temporary and include pain, swelling, and redness around the site of the injection—much like any shot—which may appear 24 to 48 hours after the actual shot. Here, experts explain what SIRVA is, how it feels, and what you and your doctor can do to prevent it. Ken Donohue, MD, a Yale Medicine orthopedic surgeon and shoulder specialist, explains to Health that SIRVA is an extremely rare condition in which pain and loss of function in the shoulder occurs following a vaccination—usually within 48 hours of administration of an injection in people who had no shoulder issues prior to injection. In very rare cases, it can result in nerve injury. Just how uncommon is it?
Most vaccines should be given via the intramuscular route into the deltoid or the anterolateral aspect of the thigh. This optimises the immunogenicity of the vaccine and minimises adverse reactions at the injection site. Recent studies have highlighted the importance of administering vaccines correctly. Injecting a vaccine into the layer of subcutaneous fat, where poor vascularity may result in slow mobilisation and processing of antigen, is a cause of vaccine failure 1 —for example in hepatitis B, 2 rabies, and influenza vaccines. Traditionally the buttocks were thought to be an appropriate site for vaccination, but the layers of fat do not contain the appropriate cells that are necessary to initiate the immune response phagocytic or antigen-presenting cells. The antigen may also take longer to reach the circulation after being deposited in fat, leading to a delay in processing by macrophages and eventually presentation to the T and B cells that are involved in the immune response. In addition, antigens may be denatured by enzymes if they remain in fat for hours or days. The importance of these factors is supported by the findings that thicker skinfolds are associated with a lowered antibody response to vaccines. The injection technique and needle size both determine how deep a substance is injected.
In order to diagnose SIRVA, an ultrasound scan is needed, which can also determine the level and type of damage. Typically, those are just temporary and include pain, swelling, and redness around the site of the injection—much like any shot—which may appear 24 to 48 hours after the actual shot. The injection sites should be separated by 1 inch or more, if possible, so that any local reactions can be differentiated. In addition, vaccine components may interact with polymers in a plastic syringe over time, potentially reducing vaccine potency. A sore arm is much better than catching the actual influenza virus —which can knock you out for days or weeks with high fever, cough and muscle aches—but why do some people experience this particular side effect of the flu shot? Section Navigation. Move Your Arm After the Shot : Moving your arm post-injection aids in spreading the vaccination away from the injection site.