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People Are Reporting Unusual Periods After Receiving COVID-19 Vaccines — Here’s What We Know

Affinia Healthcare nurse Felicia Standifer extracts a dose of the Moderna COVID-19 vaccine at a vaccination event for senior citizens at the Beloved Community United Methodist Church in south St. Louis on Jan. 23, 2021.
File photo / Kayla Drake
St. Louis Public Radio
Affinia Healthcare nurse Felicia Standifer extracts a dose of the Moderna COVID-19 vaccine at a vaccination event in south St. Louis in January.

After receiving a COVID-19 vaccine, some women are reporting heavier menstrual cycles and more cramping. To date, there are no published scientific studies about a possible link, but researchers are looking into it.

Katharine Lee, a postdoctoral researcher in the Division of Public Health Sciences at Washington University’s School of Medicine, is part of that effort. On Friday’s St. Louis on the Air, she noted that menstrual cycles are incredibly variable — a strong illness or changes in eating or exercise can alter one’s period. Plus, when the body experiences inflammation — as it does after a vaccine produces a strong immune response — the menstrual cycle is likely to change as well.

Lee herself had abnormal menstruation after receiving a COVID-19 vaccine in February. Along with researcher Kate Clancy of the University of Illinois at Urbana-Champaign, she created a survey to catalog people’s period experiences after receiving COVID-19 vaccines. Within hours of posting the survey on Twitter, they received hundreds of responses. Two weeks later, 31,000 people have completed it.

The study is ongoing, but responses so far show that abnormal periods post-vaccine are not uncommon. However, Lee was quick to stress that there’s no evidence to suggest that people should avoid getting vaccinated for this reason.

“Get vaccinated folks; it’s better than having COVID,” she said.

Lee added that post-vaccination effects on the menstrual cycle are likely short term. If irregularity continues for months, she suggested contacting a physician to rule out anything serious.

In addition to discussing what she and Clancy hope to learn from their research, Lee dispelled some false beliefs (such as COVID-19 vaccines impacting people by proximity) and offered up reasons why people should more readily talk about and study menstrual cycles.

Hear the conversation

St. Louis on the Air” brings you the stories of St. Louis and the people who live, work and create in our region. The show is hosted by Sarah Fenske and produced by Alex Heuer, Emily Woodbury, Evie Hemphill and Lara Hamdan. The audio engineer is Aaron Doerr.

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Emily is the senior producer for "St. Louis on the Air" at St. Louis Public Radio.

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