COVID 19 vaccine recipients report changes in menstrual bleeding

A new analysis of reports from more than 35,000 people offers the most comprehensive assessment so far of menstrual changes experienced by pre- and post-menopausal individuals in the first two weeks after receiving the COVID-19 vaccine. Published in the journal Science Advances, the study adds to the evidence that significant numbers of people experience this unexpected side effect.

The researchers used a survey to query people about their experiences after vaccination. Launched in April 2021, the survey asked for demographic and other information but focused on respondents' reproductive history and experiences regarding menstrual bleeding. The team downloaded the data from the surveys on June 29, 2021.

Only those who had not been diagnosed with COVID-19 were included in the analysis, as COVID-19 itself is sometimes associated with menstrual changes. The study also excluded data from people 45 to 55 years old to avoid confounding the results by including menstrual changes associated with perimenopause.

A statistical analysis revealed that 42.1% of menstruating survey respondents reported a heavier menstrual flow after receiving the COVID-19 vaccine. Some experienced this in the first seven days but many others saw changes 8-14 days after vaccination. Roughly the same proportion, 43.6%, reported no alteration of their menstrual flow after the vaccine, and a smaller percentage, 14.3%, saw a mix of no change or lighter flow, the researchers report.

Unexpected breakthrough bleeding is one of the early signs of some cancers in post-menopausal people and in those who use gender-affirming hormones, so experiencing it can make people worry and require expensive and invasive cancer-screening procedures,said researchers.

Reference: "In survey, COVID-19 vaccine recipients report changes in menstrual bleeding" UNIVERSITY OF ILLINOIS AT URBANA-CHAMPAIGN, NEWS BUREAU; JOURNAL-Science Advances; DOI: 10.1126/sciadv.abm7201.