July 22, 2022

The COVID-19 vaccines are known to cause side effects. But a new study from Kaiser Permanente suggests that an increase in postmenopausal bleeding is not one of them.

photo of Betty Suh-Burgmann, MD

Betty Suh-Burgmann, MD

The study was published early online in the American Journal of Obstetrics and Gynecology.

“We were seeing anecdotal reports that the COVID-19 vaccine was causing bleeding in postmenopausal women,” said the study’s lead author Betty Suh-Burgmann, MD, a physician researcher at the Kaiser Permanente Northern California Division of Research and a gynecologic oncologist at The Permanente Medical Group. “We believed it was important to use the data in our electronic medical records to investigate whether postmenopausal bleeding was really a common side effect of COVID vaccination.”

The study included 485,644 postmenopausal women who had been vaccinated for COVID-19 between December 2020 and May 2021. More than 95% had been vaccinated with an mRNA vaccine developed by Pfizer/BioNTech or Moderna. The researchers compared postmenopausal bleeding diagnosis rates in the 16 weeks before vaccination to rates during the 16 weeks after vaccination and rates between 16 and 32 weeks after vaccination.

A review of electronic medical records showed that 0.39% of the women experienced postmenopausal bleeding before vaccination; 0.47% had bleeding during the 16 weeks after vaccination; and 0.43% had bleeding during weeks 16 to 32 post-vaccination. In absolute numbers, this translates to fewer than 1 in 1,000 additional women with postmenopausal bleeding after vaccination than before vaccination.

photo of Julie Schmittdiel, PhD

Julie Schmittdiel, PhD

“These findings should be reassuring to women who may have put off vaccination because they had heard that the vaccines caused abnormal bleeding,” said the study’s senior author Julie Schmittdiel, PhD, a research scientist at the Division of Research. “We hope our findings will also encourage vaccine developers to look at side effects such as abnormal vaginal bleeding, along with other aspects of reproductive health, in future clinical trials.”

The study was funded by The Permanente Medical Group’s Delivery Science and Applied Research Program.

Co-authors include Cassidy Tierney, MD, of The Permanente Medical Group, and Yun-Yi Hung, PhD, of the Division of Research.

This article originally appeared in Division of Research Spotlight.