Study on the Effect of Covid-19 Vaccination on Menstrual Cycles

Dear cyclers,

I’m really excited to share results from our latest study with you that looks into the effect of the Covid 19 vaccination on menstrual cycles. As the pandemic progressed, we received a number of messages on various platforms from Cyclers, expressing concern over possible changes to their cycles, potentially induced by the vaccine. Healthcare professionals also reached out to us given that there was little research they could use to advise patients. We could not let this go unnoticed so we took your concerns to US clinicians, as well as researchers, and collectively devised a research plan to help answer them.

The results published today in a peer-reviewed US journal analyzed the cycles of nearly 4,000 US-based Natural Cycles users to determine if the COVID-19 vaccines changed cycle length or period length. All users granted us permission to use their data. The results found an average change of less than one-day in overall cycle duration following vaccination and no changes to period length. For us this was really reassuring, knowing that the majority of individuals with cycles that had received the vaccine or planned to were unlikely to experience changes to their cycle and period length.

In the rare instance that a user received two vaccine doses within the same menstrual cycle, the average change in cycle length may increase to two days, but these changes are temporary and appear to resolve quickly in subsequent cycles.

Although these findings are reassuring, they do not mean that everyone experienced little change. We still observed some whose cycle length/period length changed significantly, but they were in the minority. The menstrual cycle is both an amazing and delicate bodily function, which can be affected by many factors such as health, environment and life stressors. We recognize that any changes to your health are unnerving and as we know we are all unique so if you are at all concerned, seek advice from your healthcare professional.

At Natural Cycles our mission is to pioneer women’s health with research and passion and this is something we could not do without you! We want you to be empowered with this knowledge to be in charge of your health. Women have not been represented enough in the past when it comes to clinical research and with your help we are positively changing the course of scientific research.

Thanks again and stay safe!

Dr Jack x

Natural Cycles Medical Expert