Premenstrual and menstrual changes reported after COVID-19 vaccination: The EVA project

Abstract

Background: Menstrual disorders were not reported as a possible secondary effect in any of the clinical trials for the SARS-CoV-2 vaccines. Aim: To describe the prevalence of perceived premenstrual and menstrual changes after COVID-19 vaccine administration. Design: Cross-sectional study. Methods: A total of 14,153 women (mean age 31.5 ± 9.3 years old) who had received the full course of vaccination at least three months earlier were included in this cross-sectional study. Data including the type of vaccine administered, perceived changes in the amount and duration of menstrual bleeding, presence of clots, cycle length, and premenstrual symptoms were collected through a retrospective online survey from June to September 2021. Results: Of the women who participated in this study, 3136 reported no menstrual changes and 11,017 (78% of the study sample) reported experiencing menstrual cycle changes after vaccination. In summary, women who reported menstrual changes after vaccination were older (overall p < 0.001) and slightly more smokers ( p = 0.05) than women who did not report any changes. The most prevalent changes in relation to premenstrual symptoms were increased fatigue (43%), abdominal bloating (37%), irritability (29%), sadness (28%), and headaches (28%). The most predominant menstrual changes were more menstrual bleeding (43%), more menstrual pain (41%), delayed menstruation (38%), fewer days of menstrual bleeding (34.5%), and shorter cycle length (32%). Conclusion: Women vaccinated against COVID-19 usually perceive mild menstrual and premenstrual changes. Future studies are warranted to clarify the physiological mechanisms behind these widely reported changes.

Comment on: Premenstrual and menstrual changes reported after COVID-19 vaccination: The EVA project

“…The recent paper in Women’s Health by Baena-García et al 1 got picked up by the mainstream Portuguese media as evidence of problems associated with COVID-19 vaccines. We live in a world where papers often make the headlines for the worst reasons.…”

“…The paper lacks clarity regarding the way the sample was selected. The key statements provided in Baena-García et al 1 regarding the sampling are as follows: (1) “A cross-sectional study was conducted through an online survey.”; (2) “Data were collected retrospectively from women who had received the full vaccination course at least three months earlier . .…”

“…The key point here is “a population, or a representative subset.” The sample considered by Baena-García et al 1 is not a representative subset of the population of interest. The statement about “online survey” leaves a reader wondering how respondents were directed to the survey, that is, what potential selection bias was involved.…”

“…When faced with, as in Baena-García et al, 1 a 45 questions survey about a given topic, one is much more likely to be going through the trouble of answering it if the topic is of interest to them or if a (self-assessed) effect was observed for oneself. Either way, estimates from such a convenience sample will be biased, with bias magnitude unknown.…”

“…Self-selection bias is ignored until section “Limitations and strengths,” and the extent of the likely impacts unassessed. Convenience self-selected sample studies should be avoided unless they are able to discuss at length the potential problems of such self-selection procedures, which Baena-García et al 1 did not. In conclusion, justified by Baena-García et al’s 1 own words, .…”