A Prospective Study of the Relationship of COVID-19 Vaccination to Menstrual Cycle Characteristics in Adolescent Girls

Purpose

The current study aimed to evaluate the impact of the COVID-19 booster vaccine on menstrual cycle characteristics in adolescent girls (aged 13–20) compared to those who did not receive a booster vaccine.

Methods

This prospective study measured menstrual cycle length for three cycles prior to and four cycles after vaccination (booster group), seven cycles without vaccination (control group). Menstrual flow, menstrual pain, and menstrual symptoms were assessed at baseline and monthly for 3 months. Stress was assessed at baseline using the PROMIS Pediatric Psychological Stress Experiences scale. Generalized linear mixed effects models were used to examine the changes in menstrual characteristics.

Results

65 adolescent girls (47 booster; 18 control) were recruited via social media and from ongoing studies in the United States. Girls in the booster group experienced shorter postbooster cycles by an average 5.35 days (p = .03) compared to prebooster cycle lengths, specifically in the second postbooster cycle, while the control group did not show any changes in cycle length pre-to postbooster. Participants who received the booster in the follicular phase had shorter mean postbooster cycle length (p = .0157) compared to their prebooster cycle length. Higher stress was associated with shorter cycles (p = .03) and increased menstrual symptoms (p = <.001), regardless of group. There were no differences in menstrual flow, menstrual pain, or menstrual symptoms in either group.

Discussion

The COVID-19 booster vaccine was associated with shorter cycles in adolescent girls. These data demonstrate the need for further investigation regarding potential mechanisms of these observed changes.