An interesting study published by Edelman and others in the obstetric gynaecological journal, January 5th 2022, assessed whether COVID-19 vaccination is associated with changes in cycle or menses length in those receiving vaccination as compared with an unvaccinated cohort.  

They analysed prospectively tracked menstrual cycle data using the application Natural Cycles. 

They included US residents aged 18-45 years with normal cycle lengths about
24-38 days for three consecutive cycles before the first vaccine dose followed by vaccine-dose cycles, cycle six or if unvaccinated, six cycles over a similar time period.  

They calculated the mean within individual change in cycle and menses length and the first three cycles versus cycles four and five in the unvaccinated cohort.  

They used mixed effect models to estimate the adjusted differences in change in cycle and menses length between the vaccinated and unvaccinated individuals.

They included 3959 individuals, of whom 2403 were vaccinated and 1556 were unvaccinated.

Most of the vaccinated cohort received the Pfizer vaccine 55%, 35% received Moderna and 7% received the Johnson & Johnson. 

Overall, COVID-19 vaccine was associated with a less than one day change in cycle length for both vaccine-dose cycles compared with prevaccine cycles.

Unvaccinated individuals saw no significant change compared with the three baseline cycles.  In adjusted models, the difference in change in cycle length between the vaccinated and unvaccinated cohorts was less than one day for both doses.  

They also found that there was no change in menses length associated with vaccine.

The study concluded COVID-19 vaccination is associated with a small change in cycle length but not menses length.

The London General Practice, the leading London doctors’ clinic in Harley Street, provides a full COVID-19 diagnostic service, safety net service and multidisciplinary team help for those suffering with long COVID.

Dr Paul Ettlinger

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