Effects of SARS-CoV-2 Vaccination on Menstrual Cycle: An Italian Survey-Based Study.

Vaccination against SARS-CoV-2 has played a critical role in controlling the spread of the pandemic. The main side effects of SARS-CoV-2 vaccination include fever and fatigue; however, the potential impacts on menstrual cycles are to be determined. Given the limited number of studies suggesting menstrual changes post vaccination, this study investigates the correlation between COVID-19 vaccines and menstrual cycle changes in fertile-aged Italian women. A questionnaire was distributed from 1 October to 31 November 2022, focusing on menstrual rhythm and flow changes post vaccination. The analysis involved 471 participants. The study observed a shift from a regular to an irregular menstrual rhythm ( < 0.001), and changes in menstrual duration ( = 0.008 and < 0.001 for first and second doses, respectively) and flow volume ( < 0.001). Most patients with irregular rhythms were vaccinated in the proliferative phase of their cycle. Within six months post vaccination, 74.2% of women with irregular post-vaccination rhythms reported a return to normality. These findings indicate primarily transient menstrual changes following mRNA COVID-19 vaccination, suggesting the vaccines' safety for women of reproductive age.