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Limited, Temporary Impact of COVID-19 Vaccines on Menstrual Cycle

Limited, Temporary Impact of COVID-19 Vaccines on Menstrual Cycle

There is limited research on COVID-19 vaccination and the menstrual cycle. However, research to date has found no meaningful change in menstrual cycle length associated with COVID-19 vaccination. Two recent studies observed common, but minor, changes after COVID-19 vaccination, including:

  • Menstrual cycle length

  • Interval between cycles

  • Heavier bleeding than usual

Results from these studies indicate that people who menstruate may observe a small change in menstruation after vaccination, but changes are temporary and there continues to be no evidence that COVID-19 vaccines impact fertility.

Research Studies of Fertility in Healthy Men

  • Currently, no evidence shows that any vaccines, including COVID-19 vaccines, cause male fertility problems. A recent small study of 45 healthy menexternal icon who received an mRNA COVID-19 vaccine looked at sperm characteristics, like quantity and movement, before and after vaccination. Researchers found no significant changes in these sperm characteristics after vaccination.

    • However, one studyexternal icon found that COVID-19 infection may be associated with a decline in fertility for men for up to 60 days after infection.

  • Fever from any illness has been associated with a short-term decrease in spermexternal icon production in healthy men.18 Although fever can be a side effect of COVID-19 vaccination, there is no current evidence that fever after COVID-vaccination affects sperm production. Fever is also a common symptom of COVID-19 infection.

Safety Monitoring

COVID-19 vaccines are undergoing the most intense safety monitoring in U.S. history. Data continue to accumulate and show that COVID-19 vaccines are safe and effective for use before and during pregnancy.

Learn more about getting a COVID-19 vaccine while pregnant or breastfeeding.

Managing Side Effects

If you have side effects after COVID-19 vaccination, talk to your healthcare provider about taking over-the-counter medicine, such as ibuprofen, acetaminophen, or antihistamines, for any pain or discomfort you may experience, including fever. You can take these medications to relieve short-term side effects after getting vaccinated if you have no medical reasons that prevent you from taking these medications.

Fever, for any reason, has been associated with adverse pregnancy outcomes. Fever in pregnancy may be treated with acetaminophen as needed, in moderation, and in consultation with a healthcare provider. It is not recommended you take these medicines before vaccination to try to prevent side effects. Learn about other ways to relieve side effects.


CDC recommends that people who are trying to get pregnant now or might become pregnant in the future, as well as their partners, get vaccinated and stay up to date on their COVID-19 vaccines, including getting a COVID-19 booster shot when it’s time to get one. Pfizer-BioNTech or Moderna (mRNA COVID-19 vaccines) are preferred over the Johnson & Johnson’s Janssen COVID-19 vaccine. However, the J&J/Janssen COVID-19 vaccine may be considered in some situations.

Johnson & Johnson’s Janssen (J&J/Janssen) COVID-19 vaccine: Women younger than 50 years old should especially be aware of the rare risk of blood clots with low platelets after vaccination. There are other COVID-19 vaccines available for which this risk has not been seen. If you received a J&J/Janssen COVID-19 vaccine, here is what you need to know. Read the CDC/FDA statement.

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