News | Does the COVID-19 Vaccine Affect Menstruation? Research Provides Answers
In recent years, the lingering effects of the COVID-19 pandemic and the potential long-term effects of vaccination have drawn widespread attention. A prospective cohort study recently published in Vaccine examined whether COVID-19 vaccination affects women's menstrual cycles.
Background
Since COVID-19 vaccines were introduced, social media and vaccine safety monitoring systems have received frequent reports of menstrual changes, including longer periods, heavier bleeding, irregular cycles, and even breakthrough bleeding after menopause. These reports raised concerns about whether vaccination might affect female reproductive health.
Researchers noted that, biologically, the immune response triggered by a vaccine could briefly affect the hypothalamic-pituitary-ovarian axis and thereby influence menstruation. Earlier studies of other vaccines, including typhoid, hepatitis B, and HPV vaccines, have reported similar short-term effects.
Methods
The study used data from Pregnancy Study Online (PRESTO) and surveyed about 1,100 couples in the United States and Canada. Participants were 21 to 45 years old and had not received fertility treatment. From January 2021 to August 2022, questionnaires collected data on vaccination and menstrual characteristics.
The study focused on six menstrual characteristics, including cycle length, regularity, bleeding duration, bleeding intensity, and menstrual pain, and adjusted for potential confounding factors.
Results
After the first vaccine dose, menstrual cycles were an average of one day longer; after the second dose, they were 1.3 days longer. This change appeared only in the first cycle after vaccination and returned to normal in the second cycle.
The study also found:
The proportion of long cycles rose from about 6% to 11% after the first dose, then fell to 7.3% in the second cycle.
No significant association was found between vaccination and menstrual regularity, bleeding intensity, bleeding duration, or menstrual pain.
Regardless of vaccine brand (Moderna or Pfizer), the proportion of participants with irregular cycles (15%) did not change significantly after vaccination.
The study also found no significant effect of vaccination on fertility.
Limitations and significance
Most participants were younger women planning pregnancy and were predominantly highly educated and White, which may limit how broadly the findings apply. Participants were also followed for only several months after vaccination, and older women and other groups were not included.
Despite these limitations, the study indicates no significant long-term association between COVID-19 vaccination and menstrual function. Short-term changes may result from cytokines released during immune activation temporarily affecting the hypothalamic-pituitary-ovarian axis. Cycles subsequently returned to normal.
Conclusion
Overall, the study provides scientific evidence on the association between COVID-19 vaccination and women's menstrual cycles. The findings indicate that short-term menstrual changes after vaccination are unlikely to have a meaningful effect on fertility, helping address public concerns.
News | Does the COVID-19 Vaccine Affect Menstruation? Research Provides Answers
News | Does the COVID-19 Vaccine Affect Menstruation? Research Provides Answers
In recent years, the lingering effects of the COVID-19 pandemic and the potential long-term effects of vaccination have drawn widespread attention. A prospective cohort study recently published in Vaccine examined whether COVID-19 vaccination affects women's menstrual cycles.
Background
Since COVID-19 vaccines were introduced, social media and vaccine safety monitoring systems have received frequent reports of menstrual changes, including longer periods, heavier bleeding, irregular cycles, and even breakthrough bleeding after menopause. These reports raised concerns about whether vaccination might affect female reproductive health.
Researchers noted that, biologically, the immune response triggered by a vaccine could briefly affect the hypothalamic-pituitary-ovarian axis and thereby influence menstruation. Earlier studies of other vaccines, including typhoid, hepatitis B, and HPV vaccines, have reported similar short-term effects.
Methods
The study used data from Pregnancy Study Online (PRESTO) and surveyed about 1,100 couples in the United States and Canada. Participants were 21 to 45 years old and had not received fertility treatment. From January 2021 to August 2022, questionnaires collected data on vaccination and menstrual characteristics.
The study focused on six menstrual characteristics, including cycle length, regularity, bleeding duration, bleeding intensity, and menstrual pain, and adjusted for potential confounding factors.
Results
After the first vaccine dose, menstrual cycles were an average of one day longer; after the second dose, they were 1.3 days longer. This change appeared only in the first cycle after vaccination and returned to normal in the second cycle.
The study also found:
The proportion of long cycles rose from about 6% to 11% after the first dose, then fell to 7.3% in the second cycle.
No significant association was found between vaccination and menstrual regularity, bleeding intensity, bleeding duration, or menstrual pain.
Regardless of vaccine brand (Moderna or Pfizer), the proportion of participants with irregular cycles (15%) did not change significantly after vaccination.
The study also found no significant effect of vaccination on fertility.
Limitations and significance
Most participants were younger women planning pregnancy and were predominantly highly educated and White, which may limit how broadly the findings apply. Participants were also followed for only several months after vaccination, and older women and other groups were not included.
Despite these limitations, the study indicates no significant long-term association between COVID-19 vaccination and menstrual function. Short-term changes may result from cytokines released during immune activation temporarily affecting the hypothalamic-pituitary-ovarian axis. Cycles subsequently returned to normal.
Conclusion
Overall, the study provides scientific evidence on the association between COVID-19 vaccination and women's menstrual cycles. The findings indicate that short-term menstrual changes after vaccination are unlikely to have a meaningful effect on fertility, helping address public concerns.
Source:
Collected online