Unexpected vaginal bleeding and COVID-19 vaccination in nonmenstruating women.

The association between coronavirus disease 2019 (COVID-19) vaccination and vaginal bleeding among nonmenstruating women is not well studied. The Norwegian Institute of Public Health followed several cohorts throughout the pandemic and early performed a systematic data collection of self-reported unexpected vaginal bleeding in nonmenstruating women. Among 7725 postmenopausal women, 7148 perimenopausal women, and 7052 premenopausal women, 3.3, 14.1, and 13.1% experienced unexpected vaginal bleeding during a period of 8 to 9 months, respectively. In postmenopausal women, the risk of unexpected vaginal bleeding (i.e., postmenopausal bleeding) in the 4 weeks after COVID-19 vaccination was increased two- to threefold, compared to a prevaccination period. The corresponding risk of unexpected vaginal bleeding after vaccination was increased three- to fivefold in both nonmenstruating peri- and premenopausal women. In the premenopausal women, Spikevax was associated with at 32% increased risk as compared to Comirnaty. Our results must be confirmed in future studies.