Menstrual cycle duration was slightly altered after receiving the COVID-19 vaccine.
:Researchers examined whether vaccinations against the coronavirus disease 2019 (COVID-19) are linked to alterations in the menstrual cycle in a recent study that was published in BMJ Medicine.
Following COVID-19 vaccination, many menstrual cycle modifications have been noted, including missing periods, spotting between periods, longer or shorter cycles, and heavier or lighter menstrual flow. Unfortunately, results relating to menstruation have not been recorded in COVID-19 vaccination clinical studies. Menstruation is a very important patient-reported outcome; any change, no matter how small or how clinically significant, is very important to the general public.
Minor variations in the menstrual cycle might not be relevant to scientists or physicians, but they could be concerning for the women who experience them and fuel mistrust about vaccines. Previously, the investigators found a link between menstrual cycle alterations and COVID-19 vaccinations, but the generalizability was constrained by the sample’s exclusivity to US citizens.
Concerning the study
The current study examined the relationships between COVID-19 vaccinations and alterations in menstrual cycles in a group that was globally representative. Using Natural Cycles, a digital application for fertility awareness, the researchers examined data on menstrual cycles that had been prospectively collected. Users of the application willingly decided to track information about the menstrual cycle in the future.
A geographic location, a regular pre-vaccination menstrual cycle length, and a minimum of three cycles post-pregnancy or using hormonal contraception were requirements for participants aged 18 to 45. Data on menstrual cycles covered the period from October 1, 2020, to November 7, 2021. Data on vaccinations covered the period from January 2 to October 31 in 2021.
The study’s main exposure was whether or not participants had received the COVID-19 vaccine, and its main result was the average change in cycle duration from the average of three pre-vaccination cycles. The mean change in cycle length following the second dose and changes in menstrual cycle length following any vaccine dosage were considered secondary outcomes.
Through in-app communications, users willingly provided sociodemographic information. To compare all mean changes in cycle and menstrual lengths by vaccination status, two-sided t-tests were employed. For each result, longitudinal multivariable mixed-effects models were created. The number of dosages given per menstrual cycle was the subject of a sub-group study. To ensure that the conclusions were reliable, numerous sensitivity studies were conducted.
Menstrual cycle duration was slightly altered after receiving the COVID-19 vaccine.
The final sample consisted of 19,622 people, or 255,086 cycles, out of more than 41,000 eligible users. 80.5 percent of participants were under 35, and 33.5 percent were from Europe. The COVID-19 vaccine from Pfizer was given to two-thirds of the population, followed by those from Moderna (17.46%), AstraZeneca (9%), and Janssen (1.89%). In comparison to three pre-vaccination cycles, people in the vaccine cohort displayed a little increase ( 1 day) in the mean cycle duration during the first vaccination cycle.
In contrast, the hypothetical defined vaccine cycle showed no appreciable change in non-vaccinated people. After controlling for confounders, the difference in cycle length between the vaccinated and unvaccinated individuals was 0.71 days. Approximately 64.2% of the immunisation cohort received a second dose of the vaccine. The cycle length increased on average by 0.76 days for those who had two vaccinations, compared to 0.21 days for those who did not.
Cycle length between the groups with and without vaccinations changed by 0.56 days after confounders were taken into account. The number of people in the immunised cohort who experienced a clinically meaningful cycle length change of eight days or more was considerably higher. In the cycle following the second vaccine, the cycle length change went back to the pre-vaccination length.
Those who received two vaccine doses during the same period were mostly responsible for the lengthening of the menstrual cycle. The mean cycle length increased by roughly four days in this subgroup of 743 people. 100 of them had a cycle duration variation of at least eight days. After correction, this sub-cycle group’s length increased by 3.7 days in comparison to those who weren’t immunized.
Among those who had received vaccinations, there were no variations in the length of the menses for any vaccine dose cycle. Sensitivity analyses that included imputation/sample weighting, eliminated patients who used emergency contraception, had gynaecological conditions, and had more variable pre-vaccination cycle lengths, did not significantly alter the findings in a clinical sense.
Conclusions
In conclusion, the study discovered that, in comparison to non-vaccinated people, those who had received either vaccine dosage had an adjusted increase in the length of their menstrual cycle of 1 day. Notably, the length of the menstrual cycle increased by an adjusted 3.7 days in those who got two vaccination doses within one menstrual cycle.
In comparison to the non-vaccinated cohort, there were no appreciable changes in the length of the menses between the vaccinated patients. These results are encouraging overall and may be used to reassure people about the potential benefits of COVID-19 vaccination. Menstrual cycle modifications were noticeable after immunisation, however they were rather slight and disappeared in the following month.
