Post-Vaccine Axillary Lymphadenopathy: What a New Chest MRI Study Reveals

Emerging research out of Japan suggests that women and those who have had the Moderna COVID-19 vaccine may be more predisposed to have the vaccine-related side effect of axillary lymphadenopathy.

In a study of 433 people who had second doses of either the Moderna COVID-19 vaccine (43) or the Pfizer-BioNtech COVID-19 vaccine (390), researchers reviewed pre- and post-vaccination chest magnetic resonance imaging (MRI). The mean age of the study population was 65 years of age, and the cohort was comprised of 300 men and 133 women, according to the study, which was recently published in Radiology.

The study authors found that 40 percent of those who had the Moderna vaccine (17 of 43 study participants) developed axillary lymphadenopathy in comparison to 19 percent of study participants who had the Pfizer-BioNtech vaccine. Those who developed axillary lymphadenopathy were five years younger on average (61 years of age) in comparison to those without the side effect (66 years of age), according to the research. The researchers also found that 29 percent of women participants (39 of 133 women) developed axillary lymphadenopathy in comparison to 17 percent of men in the study cohort (51 of 300 men).

“This female predominance may indicate that females are more hypersensitive to COVID-19 vaccines just as females are more likely to develop delayed localized cutaneous reactions to the Moderna vaccine … and hypersensitivity to other vaccines,” wrote study co-author Osamu Abe, M.D., Ph.D., who is affiliated with the Division of Diagnostic Radiology at the University of Tokyo Hospital in Japan, and colleagues.

Sixty-five percent of patients with post-vaccine axillary lymphadenopathy developed the side effect within two weeks after second dose administration of COVID-19 vaccination, according to the study. Researchers noted the prevalence declined to 40 percent 15 to 28 days after the second vaccination dose and to less than 10 percent more than 56 days after the second vaccination dose.

While noting an overall 21 percent incidence of COVID-19 vaccine-related axillary lymphadenopathy in this study population, Abe and colleagues also pointed out the gradual downward trend in prevalence of the side effect within two months after the second vaccination dose. Accordingly, they advised postponing non-urgent chest imaging in this population.

“In particular at 1-14 days after vaccination, a high prevalence of lymphadenopathy may cause many false positives for malignancy and heighten anxiety of examinees,” noted Abe and colleagues. “Recommendations and guidelines should be revised for more appropriate duration of postponement and follow-up strategies based on accumulated knowledge including our results.”

In regard to study limitations, the authors note the study was conducted at one institution in Japan. They also pointed out that the study cohort was an older population (mean age of 65) due to prioritization of vaccine administration for senior citizens in Japan and that the majority of the participants were of Asian ethnicity.