Shoulder injury related to vaccine administration: commonly called SIRVA: is a rare but potentially serious complication of vaccination. Unlike ordinary soreness that improves within a day or two, SIRVA may cause persistent shoulder pain, restricted movement, bursitis, tendinitis, adhesive capsulitis, or rotator cuff problems.

Research has consistently found that women represent a substantial majority of reported SIRVA cases. Newer studies published in 2025 are adding important detail to that pattern, including the possible roles of anatomy, needle length, injection technique, and body composition.

The research does not mean that every woman faces a heightened risk of SIRVA, nor does it prove that sex alone causes the disparity. However, the findings reinforce an important point: when a shoulder injury begins soon after vaccination, women should not be told to dismiss it as ordinary injection soreness.

What recent studies found about women and SIRVA

A 2025 study published in Vaccine examined publicly available COVID-19 vaccine safety reports from January 2020 through December 2022. Among more than 1.17 billion administered doses, researchers identified 43,192 reports that met the study's criteria for SIRVA. Of those reports, 77.9% involved females.

The study estimated an incidence of approximately 3.7 SIRVA cases per 100,000 vaccine doses. Because the research relied on pharmacovigilance reports, the number should not be interpreted as a complete measure of the true incidence. Reporting practices, healthcare access, and recognition of SIRVA can all affect the data.

Still, the female predominance is consistent with earlier research. A review of conceded SIRVA petitions to the federal National Vaccine Injury Compensation Program (VICP) found that 82.8% of 476 cases were women. Most involved influenza vaccination, and many claimants reported that the injection was administered too high on the arm.

A separate 2025 study in Tomography reviewed MRI findings in 35 patients with new shoulder complaints after COVID-19 vaccination. Subacromial bursitis was the most common MRI finding, appearing in nearly 90% of cases. The researchers also found an association between female sex and subacromial bursitis in their patient group.

Taken together, these studies support a consistent observation: women make up approximately three-quarters to four-fifths of reported or evaluated SIRVA cases in several datasets. But researchers continue to study why.

Why might women be more vulnerable to SIRVA?

1. Differences in shoulder anatomy

The shoulder is not simply a large, empty area of muscle. Beneath the skin and deltoid muscle are important structures, including the subacromial and subdeltoid bursae, tendons, ligaments, and the joint capsule.

SIRVA may occur when a vaccine intended for the deltoid muscle is injected too high or too deeply, placing the needle or vaccine material into or near these structures. The resulting inflammation can cause significant pain and loss of function.

On average, women may have differences in deltoid muscle bulk and fat distribution compared with men. These differences can affect the distance from the skin to the deltoid muscle and from the muscle to the underlying bursa. However, individual anatomy varies widely. Height, weight, age, muscle mass, body composition, and the precise injection location may all matter.

For that reason, a standard needle length may not be appropriate for every adult patient.

2. Deltoid and fat-pad thickness

Needle selection is commonly based on a patient's age, sex, and weight. The goal is to use a needle long enough to reach the muscle: but not so long that it passes through the muscle and enters deeper shoulder structures.

A 2025 study published in npj Vaccines examined the depth at which a needle could reach the subacromial space in 177 patients undergoing shoulder surgery. The researchers reported that a standard 25-millimeter needle could reach the subacromial space in approximately 51.9% of the subjects when inserted at the usual vaccination location.

The authors identified a penetration threshold of approximately 16.7 millimeters and proposed that a 15-millimeter needle could reduce the risk of entering the bursa for many adults. They also found that BMI, body weight, deltoid thickness, fat thickness, and combined soft-tissue thickness were related to the depth of penetration. In multivariable analysis, BMI remained a significant factor.

This study does not establish that a 15-millimeter needle is appropriate for every patient. A needle that is too short may deposit a vaccine in fatty tissue instead of muscle, which can create other concerns. Instead, the findings highlight the importance of individualized needle selection and careful landmarking.

3. Injection location and technique

The injection site may be just as important as needle length.

Clinical guidance generally recommends administering an intramuscular vaccine in the central, thickest portion of the deltoid, approximately two to three fingerbreadths below the acromion process. The upper portion of the shoulder should be avoided because the bursa and other sensitive structures may be closer to the skin in that area.

Other technique considerations include:

• Positioning the patient so the arm and shoulder can be properly identified.
• Keeping the patient and vaccinator at a level that allows accurate placement.
• Inserting the needle at a 90-degree angle.
• Selecting needle length based on the patient's individual characteristics rather than habit.
• Avoiding an injection that is visibly too high on the arm.

The federal VICP case review found that among claimants who reported an administration error, the most common complaint was that the injection was placed too high. That does not prove that every SIRVA case resulted from a technique error, but it underscores why injection location matters.

SIRVA is more than normal post-vaccine soreness

Temporary tenderness, redness, or aching at the injection site is common after vaccination. SIRVA generally presents differently.

Symptoms that may warrant medical evaluation include:

• Significant shoulder pain beginning during or shortly after vaccination.
• Pain that persists or worsens beyond 48 hours.
• New difficulty lifting or rotating the arm.
• Substantial loss of range of motion.
• Shoulder weakness, stiffness, or nighttime pain.
• Symptoms that interfere with work, sleep, childcare, or daily activities.

SIRVA may involve bursitis, tendinitis, adhesive capsulitis, rotator cuff injury, or other shoulder conditions. An MRI or ultrasound may be recommended depending on the symptoms and examination findings. Importantly, imaging findings must be interpreted carefully because some shoulder abnormalities are common and may have existed before vaccination.

The timeline is often important. The VICP definition generally focuses on shoulder pain and limited range of motion beginning within 48 hours after vaccination in a shoulder without prior pain, inflammation, or dysfunction. Other legal and medical questions may apply depending on the circumstances.

What this research means for women considering a VICP claim

The research may help explain why women are disproportionately represented in SIRVA data, but being a woman does not automatically establish a compensable claim. A successful VICP petition requires evidence addressing the program's legal and medical requirements.

Women pursuing a potential SIRVA claim should consider taking the following steps:

Seek medical care promptly

Tell the healthcare provider when the vaccination occurred, which shoulder was injected, when symptoms began, and whether there were prior problems with that shoulder. Prompt documentation can help establish the timeline and distinguish a new injury from a preexisting condition.

Preserve relevant records

Keep vaccination records, medical records, imaging reports, bills, physical therapy records, prescription information, and documentation of missed work or reduced activities. Also write down how the injury affects everyday tasks.

Do not assume a normal X-ray rules out SIRVA

Many SIRVA-related conditions involve soft tissues that may not appear on a routine X-ray. A treating provider can determine whether additional testing is appropriate.

Be aware of deadlines

VICP claims are subject to filing deadlines. The precise deadline may depend on when the injury occurred, when symptoms began, and other circumstances. Because missing a deadline can prevent recovery, consulting a lawyer early is important.

Work with counsel familiar with vaccine injury claims

VICP proceedings are handled through the U.S. Court of Federal Claims and involve specialized procedures. An attorney can evaluate medical records, investigate the injection circumstances, identify the required proof, and help determine whether the VICP is the appropriate path.

At Braden Blumenstiel Legal Advocates Group, LLC, our approach is centered on protecting clients' rights and pursuing accountability when preventable injuries disrupt their lives. We understand that a shoulder injury can affect employment, family responsibilities, independence, and long-term health.

The bottom line

Recent research continues to show that SIRVA disproportionately affects women. A 2025 Vaccine study found that nearly 78% of identified COVID-19-related SIRVA reports involved females. A 2025 MRI study associated female sex with subacromial bursitis among the patients evaluated. Additional 2025 anatomical research raises questions about whether commonly used needle lengths may reach the subacromial space in many adults.

The reasons for the disparity are likely multifactorial. Anatomy, deltoid and fat-pad thickness, BMI, vaccination rates, healthcare-seeking patterns, reporting practices, and injection technique may all contribute.

If severe shoulder pain began soon after a vaccination and has not resolved, do not ignore it. Seek medical attention, preserve your records, and consider speaking with an experienced vaccine-injury attorney about your options.

This article is for general informational purposes only and is not legal or medical advice. The requirements and deadlines for a VICP claim can vary. A qualified healthcare professional should evaluate possible SIRVA symptoms, and an attorney should review any potential legal claim.

Sources

• Mackenzie et al., “What three years of COVID-19 vaccine administration reveals about the incidence of shoulder injury related to vaccine administration (SIRVA),” Vaccine (2025)
• Obeidat et al., MRI findings and patient demographics in COVID-19-related SIRVA, Tomography (2025)
• Kutaish et al., “More than half of shoulder vaccinations may end up in the subacromial space,” npj Vaccines (2025)
• Hesse et al., SIRVA petitions to the National Vaccine Injury Compensation Program
• University of Illinois Chicago College of Pharmacy: Recommendations to identify and manage SIRVA
• Braden Blumenstiel Legal Advocates Group, LLC: Personal Injury