Increased Risk of Subcutaneous Nodules and Lipomas Following Influenza Vaccination: A Multicenter TriNetX Cohort...

Area of Science:

• Public Health
• Immunology
• Dermatology

Background:

• Influenza vaccination is a key public health intervention.
• Rare cutaneous reactions like nodules and pruritus can occur, especially with improper administration.
• Clinic observations suggest a link between intramuscular vaccination and lipoma development.

Purpose of the Study:

• To evaluate the risk of subcutaneous nodules and lipomas in the upper arm after intramuscular influenza vaccination.
• To investigate the association between influenza vaccination and localized skin reactions.

Main Methods:

• A propensity score-matched cohort analysis was performed using the TriNetX platform.
• Compared risk of arm subcutaneous nodules and upper arm lipomas in vaccinated vs. unvaccinated individuals.
• Adjusted for potential confounders to ensure robust analysis.

Main Results:

• Individuals receiving influenza vaccines showed an increased risk of arm subcutaneous nodules (HR: 1.32, 95% CI: 1.28-1.37).
• A higher risk of upper arm lipoma development was observed in vaccinated individuals (HR: 1.57, 95% CI: 1.28-1.93).

Conclusions:

• Intramuscular influenza vaccination is linked to a higher risk of developing subcutaneous nodules and lipomas in the upper arm.
• Emphasizes the importance of correct vaccine administration techniques to reduce adverse events.
• Findings support vigilance for localized reactions post-vaccination.