Healthcare workers prepare doses of the Moderna coronavirus disease (COVID-19) vaccine before administering them to staffers of Japan's supermarket group Aeon at the company's shopping mall in Chiba, Japan, June 21, 2021. (Photo:REUTERS)

The study of more than 5,800 participants between May and November last year showed that 22.4% of women developed delayed skin reactions after the first shot, compared to 5.1% of men.

The symptoms were mild and not considered a contraindication of the mRNA-based vaccine, according to the June 1 report in the Journal of the American Medical Association.

Delayed skin reactions, happening on or after six days from the shot, have been also reported as a rare adverse event in the United States and Europe, according to the authors from Tokyo's Self-Defense Forces Central Hospital.