--- title: COVID-19 Vaccines Not Strongly Linked to Menstrual Changes description: The study is among the first to look at more severe bleeding events and changes in menstrual cycles after COVID-19 vaccination. canonical: https://time.com/6276989/covid-19-vaccine-period-changes/ author: Alice Park article:opinion: false article:content_tier: free article:published_time: 2023-05-04T14:43:34.000Z article:modified_time: 2026-08-04T07:51:14.519Z article:section: Health og:title: COVID-19 Vaccines Aren't Strongly Linked to Menstrual Changes, Study Says og:description: The study is among the first to look at more severe bleeding events and changes in menstrual cycles after vaccination og:url: https://time.com/6276989/covid-19-vaccine-period-changes/ og:site_name: TIME og:image: https://static.time.com/v3/assets/bltea6093859af6183b/bltd1c1395cdc601035/698a3c8686f68e68376f2660/GettyImages-1303038502.jpg?branch=production&width=1200&quality=75&auto=webp&crop=16:9 og:image:width: 2155 og:image:height: 1212 og:image:alt: covid-19-vaccination og:type: article twitter:card: summary_large_image twitter:title: COVID-19 Vaccines Aren't Strongly Linked to Menstrual Changes, Study Says twitter:description: The study is among the first to look at more severe bleeding events and changes in menstrual cycles after vaccination twitter:image: https://static.time.com/v3/assets/bltea6093859af6183b/bltd1c1395cdc601035/698a3c8686f68e68376f2660/GettyImages-1303038502.jpg?branch=production&width=1200&quality=75&auto=webp&crop=16:9 ---  # COVID-19 Vaccines Aren't Strongly Linked to Menstrual Changes, Study Says > Sponsored content. 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Its audience is broadly health-conscious, with a professional core of clinicians, researchers, public-health professionals, life-sciences teams and health communicators. ### Sources * TIME Newsletters: [time.com/newsletters](/c/time-nl-health-2026q3/newsletters?i=70efab5f-6da7-4d25-b6ca-c0d3a8ba49c2&cr=time-nl-health-2026q3-v1) ## Video: The Race to Make a Vaccine for Breast Cancer [Watch (HLS stream): The Race to Make a Vaccine for Breast Cancer](https://cdn.jwplayer.com/manifests/W5jcvwLu.m3u8) (8:09)  _Published 2022-10-05. Scientists believe there is a future in which women can be vaccinated against breast cancer._  by [Alice Park](https://time.com/author/alice-park/)  ## Alice Park Senior Correspondent May 4, 2023 2:43 PM UTC  Using a syringe to attack the new covid-19 variant. A young doctor in a white protective glove holds a medical syringe and a vial. Using a syringe to attack the new covid-19 variant. A young doctor in a white protective glove holds a medical syringe and a vial. Getty Images  by [Alice Park](https://time.com/author/alice-park/)  ## Alice Park Senior Correspondent May 4, 2023 2:43 PM UTC While the COVID-19 vaccines have made a dramatic difference in controlling the pandemic, researchers are still learning about the ways that the shots may affect people’s health. One of those questions centers around how the vaccines might impact menstrual cycles. [Reports](https://time.com/6217115/covid-19-vaccines-period-longer/) of women experiencing changes in their cycles—either in the intensity and frequency of bleeding, or the length of their periods—have prompted more rigorous investigations of how COVID-19 vaccines may be affecting cycles. In the latest [study](https://www.bmj.com/content/381/bmj-2023-074778), published in the _BMJ_, researchers led by Rickard Ljung, professor of epidemiology and physician specialist at the Swedish Medical Products Agency (the country’s equivalent to the U.S. Food and Drug Administration), looked at medical records from nearly 3 million Swedish women, ages 12 to 74\. They focused on those who had sought care from health care professionals for menstrual changes from Dec. 2020 to Feb. 2022 and were able to see when the women were vaccinated and how long after their immunization they sought care. That analysis found no strong association between COVID-19 vaccines and changes in menstruation—or at least bleeding events that were severe enough for women to seek medical care. --- ### More from TIME --- **Read More**: [_Why It’s So Hard to Have Your Fertility Tested_](https://time.com/6253707/fertility-testing-difficult/) The strongest association was among post-menopausal women. After a third dose (the booster) of either mRNA vaccine, made by Moderna or Pfizer-BioNTech, women had a 28% increased risk of bleeding in the first week after vaccination, and about a 25% increased risk of bleeding through the next three months, compared to before their vaccination. Ljung says that pattern doesn’t necessarily suggest an association between the two events, especially since a similar increase was not seen among premenopausal women. Ljung says that the association among post-menopausal women could be confounded by a number of factors, including the fact that they might be more attuned to bleeding events and more likely to see a physician than younger women, who may attribute any bleeding to irregular periods. Also, given that the data captured doctor’s visits, it’s unlikely that women would have been able to get an appointment with a physician within a week if they developed bleeding after getting vaccinated. “That’s a very short time to get that kind of appointment,” says Ljung. The pattern, he says, doesn’t support a possible causal connection between vaccination and changes in menstruation, and it’s likely the association seen among post-menopausal women might be reflecting other factors. The results don’t necessarily contradict the growing number of [reports](https://time.com/6198573/covid-19-vaccines-periods-mentrual-cycles/) of [changes in menstruation](https://time.com/6217115/covid-19-vaccines-period-longer/) following COVID-19 vaccination. Periods can be affected by any vaccine, but the current study shows that those changes might not be serious enough to require medical attention. “It’s a bit reassuring that there doesn’t seem to be an increased risk of more severe menstrual disturbances, bleeding, or other changes after vaccination,” says Ljung. Still, doctors don’t fully understand why immunization against COVID-19 could affect menstrual cycles, so more research is needed to appreciate how developing immunity against SARS-CoV-2 affects health. ## Transcript Vaccines are often called The Miracle of modern medicine for their ability to Target the immune system against disease-causing, viruses and bacteria. Since they work against infectious diseases, why not against other conditions that have long plagued Humanity like cancer. To say we're working to develop a vaccine to prevent Cancers and individuals for the rest of your life. It sounds like Star Wars but it's not a concept that's totally unchartered me vaccines against human papillomavirus which is causative agent in certain types of human cancers. Work to prevent cancer in those individuals who get vaccinated and so are we? We no longer is nikoli more about the immune system in the last 20 years in the face of cancer. Studies and cancer. And now it's covid that we can bring this knowledge to this big goal of using a new system to prevent all types of cancers and and do so with humility and optimize the immune response against cancer by training cells to recognize tumors as foreign. Once that happens in breast cancer, it may be possible to not only prevent Prince's in people who have already had cancer, but to even prevent it in the first place, I was diagnosed in 1987 and I wasn't treated much differently from what the treatments or today. Oh, wow. Yes, there's a lot of focus on immunotherapy and that's exciting. It's exciting from a research perspective but it hasn't really made a difference in women's lives. Yet, we believe that a vaccine approach is certainly the key and primary prevention or preventing people from getting breast cancer to begin with because we believe that that is the future, that that is one of the areas that we should be focusing on now. We believe not only will it save lives, but it will also be less toxic than existing Therapies. You know, technologies that have have been developed over the past five to ten years. Are number one, immune checkpoint Inhibitors. So, immune checkpoint Inhibitors is a form of therapy that has been you know now approved by the Food and Drug Administration for use in targeting a number of different cancers were, we had has been effective lasso in in certain tumors. And so, the reason that vaccines don't work against metastatic deposits of tumor is because the tumors themselves. Throw up a number of Walls that ultimately prevents the immune response from acting and killing the tumor. So the whole idea just like an infectious disease, vaccine used to identify what's foreign in the tumor as much as possible and to really craft A vaccine that targets what's foreign because that's really word. You know we're going to see the power of the immune response and in shrinking or preventing a cancer is having multiple targets within the tumor. But also having them be very foreign at the Mayo. Clinic Newton has developed a vaccine targeting, a very early form of breast cancer called ductal carcinoma inside you or DC, is he is working with his colleague dr. Amy degnan to test that vaccine experts, have debated in recent years, whether dcis is actually cancer since it involves lesions that remain in the ducts of the breast tissue and don't spread throughout the breast as other forms of breast cancer. Do about 50 1,000 women. A year are diagnosed with DC is in the US and some of those cases will become cancerous. Although doctors, can't predict which one As a result many women with the condition up to have radiation and surgery to remove the lesions to avoid the risk of developing cancer. if the immune system could be trained to attack tcis instead that would potentially help women to avoid the more invasive treatments, which some experts believe might be over treating their condition We are interested in pushing forward, you know, toward a goal of vaccines for breast cancer prevention. And so one strategy to do that is to then evaluate a vaccine that we found was safe and women who had invasive cancer and apply it to women who don't have invasive cancer yet who have this dcis and evaluate what kind of immune response we see in those women. And one of the things that were specifically interested in this study to see is what kind of response do we see in the breast tissue after this vaccine is given, can we find evidence that the immune system is reacting to the vaccine and potentially, you know, trying to clear out these cancer cells in the breast tissue. So, in this trial, we give the vaccine for several doses of the vaccine before surgery, and women who have dcis. And then at the time of We're removing their dcis as we would not normally to treat it, but we're also able to then investigate the breast tissue and the area of DCs and and see what is happening with the immune response there after the vaccine, the team at the Abramson Cancer Center, at Penn Medicine, is studying a different approach to a breast cancer vaccine. They are currently a rolling about 16th bull who have been diagnosed with cancer and who have the genetic mutations, bcra one or bcra to which put them at higher risk of developing breast cancer to see if vaccinating them will lower their chance of recurrence. The researchers also had to study a couple dozen people with the genetic risk, but who has not yet been diagnosed with cancer to see if the vaccine could lower their risk of ever developing the disease. It's a, it's a game changer and we recognize that we have a ways to go. But right now, if you're a 25 year old woman who has undergone genetic testing and is told that you have a safe for me to yishun, you're talkin about raining for the rest of your life for your breasts or deciding to do a bilateral, mastectomy have your breasts removed and at this point we had no effective screening for ovarian cancer. And so we strongly recommend that individuals have their ovaries removed between ages, 35 and 44 a beer, signaling carrier, putting them into early menopause. And with all the attendant Dallas ring consequence that we really have not had great options apart from surgical options. And, you know, we're working on many different types of strategies to try alternative National the natural history. But this concept of immune interception being able to use the immune system to change the natural history for these individual is so critical. We are probably at the end of the era of using cancer, vaccines with great hope in a patient, whose party been treated with everything in the tumor is still Advanced to using these vaccines and all our new knowledge in patients, who are at risk for relapse or individuals who are simply a high risk for cancer and we want to prevent so prevention. 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