Timing of COVID-19 shot can change menstrual cycle length

OHSU researchers find temporary cycle length changes associated with vaccination during first half of menstrual cycle

By Nicole Rideout February 29, 2024 Portland, Oregon

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COVID-19 vaccination timing and menstrual cycles 2

In a new study, OHSU researchers found a link between COVID-19 vaccine timing and changes in menstrual cycle length. Analysis of nearly 20,000 individuals finds a temporary increase of one day among those who received a vaccine in the first half of their menstrual cycle. (OHSU/Christine Torres Hicks)

COVID-19 vaccination timing and menstrual cycles 1

Catriona Spilde, a resource nurse at the Casey Eye Institute, receives flu and COVID-19 vaccinations administered by Lilian Kim, an OHSU School of Dentistry student. In a new study, OHSU researchers found a link between COVID-19 vaccine timing and changes in menstrual cycle length. Analysis of nearly 20,000 individuals finds a temporary increase of one day among those who received a vaccine in the first half of their menstrual cycle. (OHSU/Christine Torres Hicks)

Alison Edelman, M.D., MPH

Alison Edelman, M.D., M.P.H., joins a World Health Organization advisory group to improve sexual and reproductive health globally. (OHSU/Christine Torres Hicks)