Shoulder Injury Related to Vaccine Administration (SIRVA)

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Shoulder Injury Related to Vaccine Administration (SIRVA)

  • the deltoid muscle is the ideal site for achieving excellent immunity when giving vaccine injection - however, vaccine injections are not without risk, and if the injectate reaches unintended places, it can produce a vigorous immune response where it is not wanted, especially in pre-primed individuals.
    • all parts of the shoulder joint apparatus have been affected in this way, from the bursa under the deltoid, down to the underlying bone itself

    • in 2010, the title "SIRVA" [ Shoulder Injury Related to Vaccine Administration ] was coined in the United States, as an umbrella term for complications arising within 48 hours of vaccination, which result in significant shoulder pain and movement restriction, where none had existed before

    • an in-depth study of VAERS [Vaccine Associated Event Reporting System] following flu jabs, concluded that shoulder problems accounted for 2% of reports [Hibbs et al], and by 2020, over half of the claims for compensation post-vaccination in the States were for VAERS

    • vaccine associated medically attended injection site events data following deltoid intramuscular injection can be divided into 3 groups (1)
      • nerve palsies
        • radial nerve and the anterior branch of the axillary nerve are susceptible to injury following intended intramuscular injection into the deltoid muscle
          • radial nerve is susceptible to injection injury where it passes obliquely around the upper humerus, proximal to and in the spiral groove which ends just distal to the deltoid tuberosity on the lateral margin of the humerus
          • radial nerve palsy is the second most common traumatic injection neuropathy seen in developing countries and in this setting is due to injections being given by untrained and unlicensed practitioners
        • anterior branch of the axillary nerve takes a tortuous path around the surgical neck of the humerus and provides motor innervation to the anterior and middle parts of the deltoid muscle

      • musculoskeletal injuries
        • deltoid muscle covers the subacromial/subdeltoid bursa proximally and the humerus distally.
          • bursae are intimately related and in direct communication with each other in 80% or more of patients and cover the tendons of the rotator cuff (supraspinatus, infraspinatus, subscapularis and teres minor) which provide dynamic stabilization of the glenohumeral joint
          • Magnetic Resonance Imaging (MRI)
            • offers a paradigm shift in the diagnosis and management of medically attended injection site reactions as it allows concurrent assessment of both soft tissue and bony injury following vaccination (1)
        • bone and articular injury
          • cases of periosteal reaction (boney contusion) following vaccination have been reported
        • osteonecrosis
        • intra-articular injection
        • subacromial/subdeltoid bursitis/rotator cuff tendinopathy

      • cutaneous reaction
        • can be divided into 3 groups; sequelae of inadvertent subcutaneous rather than intramuscular injection, local sepsis and vascular complications
          • possible adverse events due to inadvertent subcutaneous rather than intramuscular injection:
            • subcutaneous nodules
            • localized lipoatrophy
            • sterile abscess
              • the Brighton Collaboration Local Reactions Working Group for abscess at injection site defined a sterile abscess with level 1 diagnostic certainty as - spontaneous or surgical drainage from the mass AND material obtained from the mass prior to initiating antimicrobial therapy, but with negative evaluation for infectious etiology (which may include Gram stain, culture or other tests)
            • non-infectious subcutaneous emphysema
          • local sepsis
          • vascular complications
            • Nicolau Syndrome or embolia cutis medicamentosa is a rare complication of intramuscular injection of medications leading to ischemic necrosis at the injection site due to direct trauma to vascular structure or trauma induced vasospasm or a combination of both mechanisms

    • in the UK there is not yet equivalent research, and the issue is not easy to analyse
      • SIRVA is a medico-legal term, and there is no SNOMED code for it, but it is listed in our Yellow Card reporting system for suspected reactions

A practical guide to reducing the risk of SIRVA

What's the Problem ?

  • Immunisation injections are the key to our successful disease prevention campaigns. But even in practiced hands, a vigorous response can develop in unwanted places if the injectate is not placed in muscle. (2)
  • The commonest reactions are in superficial tissues.
  • With misplaced deltoid injections the underlying joint mechanism can develop bursitis* frozen shoulder/periarthritis*, or rotator cuff disease* [affecting one or more tendons].
  • Bone and cartilage can be affected.
  • The nearby axillary and radial nerves have also been injured, though not often.
  • Deeper injuries can take time to recover and be debilitating.
  • US studies following flu jabs concluded that 2% of adverse events were " Shoulder Injury Related to Vaccine Administration ", [SIRVA]*, lasting from 7- 365 days. (1)
  • In 2020 over 50% of the claims there, post-vaccination, were for SIRVA; expert opinion blamed poor vaccination technique.
  • No systematic study has been done in the UK, but even with Lockdown, Yellow Card Reports of suspected shoulder reactions* to COVID vaccinations numbered 1,570 by March 2022. (3)

These consequences are avoidable…

Where to inject then ?

  • Halfway down the deltoid muscle is the accepted wisdom, where it is usually thick.
    • But some simplified training diagrams may not explain the muscle properly, as here:

Fig 1 - Training programmes tend to use simplified diagrams that can be misleading, like this

The deltoid is triangular with its point downwards.

  • The target [central] section runs vertically down from the acromion.
  • The tip of the muscle is halfway down the humerus.
  • The V-shaped insertion [4-5 cm long], gets more fibrous below the axillary skin folds, and is usually avoided.

Fig 2 - Explains the following views of a cut shoulder (Fig 3, Fig 4 and Fig 5)

At Risk Structures

  • Directly under the upper third of the deltoid are:
    • The compressible and highly mobile bursa [which doesn’t extend beyond the axillary nerve.
    • The joint capsule.
    • The rotator cuff muscles/tendons.
    • The articular cartilage and bone.
  • Further down:
    • The axillary nerve and accompanying blood vessels.
    • When measured below the acromial edge by ultrasound of the skin surface, these can lie as far as 9.2 cm in the adult male, and 7.7 in the adult female (4).
    • Radial Nerve:
      • This nerve and its vessels pass downwards behind the posterior part of the deltoid, spiralling round the humerus alongside its insertion..avoid this part ! (5)

Fig 3 Vertical section through midline of deltoid

Key to photograph

Handy Protection Guide!

  • The patient's opposite hand can serve as a guide.
  • Swing across and align so the top of the index lies along the lower edge of the acromion.
  • This covers the vulnerable structures [Figs 4, 6] (5)
  • This must be the patient's OWN hand, NOT the vaccinator's, which may not be in proportion.
  • The target zone remains in a line vertically below the midpoint of the acromion. [Fig 6]
  • Other positions; arm resting on desk, hand on hip, etc, alter the anatomy under the skin.

Fig 4 - "Target Zone" (green)

  • NB It should be the patient’s own hand and NOT the vaccinator’s, as these may not be in proportion


  • Most vaccines need to be injected into muscle.
  • A 25mm needle will reach muscle in adults of average build. (6)
  • Deposition in subcutaneous fat is more likely to suffer a reaction, so in large individuals, longer is recommended…
  • Adult males over 118kg [18st 8lb], and females over 90kg [14st 2lb] require 38mm.
  • With small subjects or slim build, 25mm needles may reach bone, so caution and judgement are required. [Fig 5]
  • American guidelines still mention the 16mm option for adults females below 60kg [9st 6lb]. (7)
  • The risk of over-penetration in childrens’ arms, is high. (8)

Fig 5 Needle depth should be to suit the individual

Fig 6 - Target area (in green) X = Avoid the posterior part of the muscle

  • Summary
    • sit the patient
    • let the arm hang loosely down at the side, with the hand in its relaxed, neutral position
    • place the patient's own hand, with the top of the index along the lower border of the acromion
    • inject in the mid-line, between the little finger and the level of the armpit skinfolds, (a 2-3cm target in adults)
    • get on a level to check, and inject at 90 degrees to the skin surface
    • use a 25mm needle for adults of average build; longer for large individuals; shorter for slim or small subjects

  • Key Learning Points:
    • the mid-point of the deltoid is usually recommended for vaccinations; structures above this level do get damaged
    • you will get the mid-point wrong if you don’t know the full extent of the muscle
    • moving the arm arm into different positions [resting it on a desk, placing the hand on the hip, +c], alters the anatomy under the skin
    • think about the needle length for each patient
    • and most importantly:
      • it is safer to aim a fraction below the midpoint, than to go above it


  • You will get the deltoid's mid-point WRONG if you don’t know its full extent.
  • It's safer to go a fraction below the mid-point, than above.


  • Alan Walker Retired GP , and Ex-Anatomy Lecturer; Affiliated to Hull York Medical School, and the Primary Care Rheumatology and Musculoskeletal Society


  • Cadaveric imaging taken with appropriate donor consent from Hull York Medical School. Especial thanks to the donor and their family; to HYMS colleagues, Rachel Cunningham and Martin Walters, for their assistance; to those who added constructive criticism; and to my family, as always.


  1. Hibbs BF et al. Reports of atypical shoulder pain and dysfunction following inactivated influenza vaccine, Vaccine Adverse Event Reporting System [VAERS], 2010-2017 Vaccine. 2020; 38:1137-1143 htpps//
  2. Cook IF. Best vaccination practice and medically attended injection site events following deltoid intramuscular injection. Hum Vaccin Immunother. 2015; 11[5]1184-1191 htpps//
  3. MHRA Coronavirus vaccines adverse reactions. Yellow Card Reports up to 23/2/2022
  4. Nakajima Y, Mukai K, Takaoka K, et al. Establishing a new appropriate intramuscular injection site in the deltoid muscle. Hum Vaccin Immunother. 2017; 13: 2123-2129
  5. Walker A, You know where you can stick that !!…or do you ? Where to inject the deltoid, and why. Practice Nursing. 2021; 32 [5]; 189-193
  6. Poland GA, Borrud A, Jacobson RM, et al. Determination of deltoid fat pad thickness. Implications for needle length in adult immunization.
    JAMA. 1997; 277 [221]: 1709-1711
  7. The Pink Book: Epidemiology of Vaccine-Preventable Diseases. Centers for Disease Control and Prevention, USA, 2021
  8. Lippert WC, Wall EJ. Optimal Intramuscular Needle Penetration Depth. Pediatrics. 2008; 122 [3]: e556-e563.

Last edited 05/2022 and last reviewed 05/2022