A groundbreaking study, published on 25/11 in PNAS, reveals that tattoos may have a potential impact on the body's immune response to various vaccines.

The research explains that tattoo ink, while fading, is not eliminated from the body. Instead, it permeates nearby lymph nodes, where it can destroy key immune cells and alter the body's response to certain vaccines administered in the same region, such as covid-19 and flu vaccines.

Experiments on mice revealed that within minutes of tattooing, ink traveled through the lymphatic system, accumulating in lymph nodes and increasing over two months. Macrophages, crucial for initiating immune responses to vaccines and infections, absorbed the ink, making them more vulnerable. Additionally, lymph nodes in tattooed skin showed prolonged inflammation.

Tattoos can affect the efficacy of some vaccines. *Vecteezy*

To assess this impact, the team vaccinated mice in both tattooed areas (with ink-laden lymph nodes) and untattooed skin. Results showed a significant decrease in antibody response to the mRNA covid-19 vaccine, with lower sars-cov-2 spike protein levels in macrophages, indicating reduced protection. Conversely, the response to the inactivated flu vaccine increased, particularly with black and red inks, suggesting an inflammatory adjuvant effect. This implies that inflammation and pigment overload from tattoos can hinder some vaccine platforms while enhancing others, rather than producing a consistent outcome.

In human studies, scientists analyzed lymph node biopsy samples from tattooed individuals. They found the nodes were discolored, laden with pigment-carrying macrophages, and showed signs of chronic inflammation.

While this study did not directly assess human vaccine responses, prior research has suggested a concerning link between tattoos and cancer. For example, a study in Denmark (2025) found that tattooed individuals face an elevated risk of skin cancer (melanoma, squamous cell carcinoma) and lymphoma, particularly with tattoos larger than the palm of a hand. Similarly, a 2024 study in Sweden involving nearly 12,000 people reported a 21% increased risk of malignant lymphoma among those with tattoos.

Researchers advocate for closer monitoring of tattoo ink toxicity and its immune impact, given the growing popularity of tattoos. They advise against immediate changes to vaccination schedules but suggest considering tattoos as an environmental factor that could influence vaccine design, dosage, and injection site guidance, particularly for newer platforms like mRNA.

By Van Ha, citing Gavi and PNAS.