I just saw this - apologies if it's been posted before.
'Scientists launch study to find out if COVID-19 vaccines are causing period changes after hundreds of women notice irregularities'
Also US based, so perhaps won't apply here, but still may be of interest.
www.dailymail.co.uk/health/article-9495727/Researchers-studying-women-report-changes-periods-taking-COVID-vaccine.html
The comments are veering into some pretty wild conspiracy theories, but I found it really interesting that there is potentially an impact on periods - especially after learning about immunity and oestrogen, etc.
Some very complex interactions, perhaps?