Oct 6, 2022 – Pamela Jock always had regular periods, even when she was around 50 and knew perimenopause was on the horizon. But shortly after receiving the second of a two-row COVID-19 shot in June 2020, her cycle began to change. At 52, it could indeed be perimenopause, but Jock had to wonder if the vaccine might have played a role. It turns out the answer to their speculation is “maybe.”
A new study recently published in the BMJ, has delved deeply into the possible link between the COVID vaccine and irregular periods. The research, led by Alison Edelman, MD, professor of obstetrics and gynecology at Oregon Health & Science University, was prompted by more than 30,000 reports of cycle changes to the UK’s Medicines and Healthcare Products Regulatory Agency (MHRA).
Using data from a period tracking app called Natural Cycles, the study pulled together numbers from more than 20,000 women from around the world. The researchers looked at the three menstrual cycles before vaccination and at least one cycle after. They compared this to four menstrual cycles in a group that had not received the vaccine.
The results showed that the vaccinated women got their period on average 0.71 days after the first vaccination. For those who received two vaccines in one cycle, the cycle lengthened by an average of 4 days. This follows up with Jock’s experience. “My cycle lengthened to 30 days compared to my normal 26 days,” she says. “Then I had a break between cycles of a few months.”
This is where the connection between the vaccination cycle becomes unclear. Given Jock’s age, her big gap between cycles could very well be perimenopause, especially since the study only looked at women between the ages of 18 and 45 who were already having regular cycles. But Jock still wonders. “After I got my first booster shot in the fall of 2021, my periods went back to normal and started occurring every 26 days,” she says. “But they were extremely heavy and I was tired and drained.”
Follow-up blood tests revealed anemia, possibly as a result. When asked about a possible link between the vaccine and irregular cycles, Jock said, “The doctor didn’t think there was a link and that it was probably perimenopause.”
Whether in the study participants’ age group or beyond, like Jock, the relationship between the COVID vaccine and menstrual cycle changes may be due to several things, he says Esther Goldsmith, exercise physiologist at bioanalysis company Orreco.
“It can be affected by when in your cycle you get your vaccine,” she says. “We know that changes in estrogen and progesterone in the menstrual cycle can affect the immune system and our immune response. So I think it’s really interesting that the study shows that those who received two doses in the same cycle were most affected.”
Orreco’s data collection – which often focuses on female athletes – has shown that the vaccine may also have other effects that may play a role.
“We also saw that the vaccine can affect oxidative stress and inflammation, things that we measure through point-of-care blood tests,” says Goldsmith. “Inflammation can affect symptoms, so by inference the vaccine may also cause a change in menstrual cycle symptoms.”
Shaghayegh DeNoble, MD, with advanced gynecology and laparoscopy from North JerseyShe says she hears from many patients that their periods came later than expected and/or that they had heavier than normal periods after being vaccinated – as well as after being infected with COVID.
“I remind them that many things can alter our cycles, including travel, the changing seasons and stress,” she says. “It happens all the time and there are no long-term effects. I assure you that your cycles will return to normal.”
The research found that in most cases, normality returned within one to two cycles after vaccination, which is also consistent with what DeNoble’s patients reported.
While research may have identified a likely link between the vaccine and abnormal menstrual cycles, Goldsmith and DeNoble both stress that the vaccines do not affect fertility.
“I get so many calls from women who are concerned that their fertility might also be at risk because they don’t have their periods,” says DeNoble. “But fertility is not affected by the vaccine.”
Jock says she’s grateful that fertility is no longer important to her. “I’d probably be concerned if it were,” she admits.
Goldsmith says such fears are unfounded and wants women to put any alarms to one side. “An abnormal period is a very natural response to something that is physiologically a big event for your body,” she says. “Menstrual cycles can be incredibly sensitive to changes of all kinds, be it diet, lifestyle, stress or the immune system. So we shouldn’t be surprised that it’s responsive to things like vaccines. This is probably not a new phenomenon, but it may not have been documented in the past.”
Now, armed with the research, DeNoble says it will be easier to educate patients about what to expect from boosters.
“It’s so important for us to be able to warn patients about possible side effects,” she says, “and it’s also important that we can reassure them.”
Goldsmith recommends women track their cycles and document any changes – vaccination or not.
“We should all be mindful of our cycles and make sure we’re taking care of ourselves during these times to reduce the stress that the body is putting on,” she says.
While Jock will never know for sure if her irregular cycles were the result of the vaccine or perimenopause, she’s watching what happens when she gets the bivalent COVID vaccine soon. “I’m curious if this will put me on the same track,” she says.
Regardless of the inconveniences of an abnormal cycle, Jock has no regrets about the vaccine, she says: “I would much rather stay healthy and avoid COVID.”