Background: Many studies have reported irregular menstruation in women of childbearing age after vaccination or infection with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). However, no studies have discussed the changes in menstrual patterns after reinfection with SARS-CoV-2 after vaccination. This study aimed to evaluate the effect of SARS-CoV-2 infection on menstruation in vaccinated and unvaccinated women of reproductive age. Methods: This retrospective study analysed the menstrual data of 241 women of childbearing age. Between December 8th, 2022 and February 11th, 2023, 201 participants were diagnosed with SARS-CoV-2 infection (observation group), while 40 remained uninfected (control group). The Chi-square test and Fisher’s exact test were used to assess menstrual irregularities among the participants. Logistic regression analysis was performed to determine the factors influencing menstrual patterns. Results: Among the 241 women who completed the survey, approximately one-third experienced changes in their menstrual patterns, including a shortened cycle (30.3%), a prolonged duration (13%), a decreased volume (24.9%), and increased dysmenorrhea (9.9%). Over half of the infected women did not experience any changes in their menstrual pattern. Only changes in the menstrual volume were statistically significant (p = 0.003). Logistic regression revealed that vaccination may be a protective factor against changes in the menstrual cycle (p = 0.036, odds ratio (OR) = 0.703, 95% confidence interval (95% CI): 0.506–0.977) and volume (p = 0.032, OR = 0.700, 95% CI: 0.505–0.969) after SARS-CoV-2 infection. Conclusions: SARS-CoV-2 infection did not appear to affect menstruation in vaccinated women. There were no significant changes in menstrual patterns except for menstrual cycle in women infected with SARS-CoV-2 after coronavirus disease 2019 (COVID-19) vaccination. In addition, vaccination seems to be a protective factor against changes in the menstrual cycle and volume after SARS-CoV-2 infection.
