Can the COVID Vaccine Affect My Period?

Updated 1/19/22

For months, social media has been buzzing with stories about changes in the menstrual cycle after getting the COVID-19 vaccine. Researchers have wrapped up one of the first studies investigating this link, and the verdict is you may notice a slight, temporary change.

In tracking about 4,000 U.S. women through six menstrual cycles researchers found that, on average, the next period after a COVID shot started about a day later than usual. A smaller number of women within the vaccinated group – about 350 -- got both vaccine doses in the same menstrual cycle, resulting in about a two-day change to their next cycle.

And while there had been some anecdotal connections made between the vaccine and a change in the length of the next period, the study didn’t find evidence to support any effect on duration.

It’s been widely studied that changes in a women’s menstrual cycle can be caused by a host of things including stress, lack of sleep, exercise and some medications. And if you’re really sick -- with any illness -- there’s a chance that stress could affect your period. Hormones act as signals to your brain during the menstrual cycle, and those signals can be disrupted when the body is affected by an infection or even a vaccine. With the COVID virus itself, there have been some studies showing that it creates stress on the body, leading to irregular menstrual cycles for some.

If the change in your menstrual cycle is extreme, like going through a pad an hour, or if that one “off” cycle turns into three or more in a row, call your doctor. There is likely something else at play.

Side note: there’s no reason not to get vaccinated when you have your period, according to both the CDC and the American College of Obstetricians and Gynecologists. If you’re looking to make an appointment to get the