The National Institutes of Health has awarded one-year supplemental grants totaling $1.67 million to five institutions to explore potential links between COVID-19 vaccination and menstrual changes. Some women have reported experiencing irregular or missing menstrual periods, bleeding that is heavier than usual, and other menstrual changes after receiving COVID-19 vaccines. The new awards support research to determine whether such changes may be linked to COVID-19 vaccination itself and how long the changes last. Researchers also will seek to clarify the mechanisms underlying potential vaccine-related menstrual changes.