It's unfeasible to carry out research on every little aspect of any medication, except for the very long term. That's why drugs get approved all the time, yet trials and studies continue for decades to account for long term and extremely rare side effects.
That said, literally anything can change the menstrual cycle (flu, stress, changes in nutrition or exercise levels), and especially given that menstrual symptoms correlate more with inflammatory markers than with actual hormone levels [0], it's to be expected that treatments that elicit an inflammatory response might have an effect in menstrual symptoms. It's good this research is done, but I doubt these changes come up as a surprise to any physician.
> Is it ethical to enforce vaccinations (via mandate) with these matters unresolved?
I think so, unless you consider to keep enforcing lockdowns, travel restrictions, or a Children-of-the-corn-light type of scenario to be ethically better.
Well, a lot of places that have high vaccination rates still have domestic restrictions, or are considering bringing them back as they deal with new surges in COVID cases. International travel restrictions are still significant, even for fully vaccinated travelers.
See: Israel, Singapore, UK, Belgium to name a few
The vaccines do appear to offer good protection against hospitalization and death, which is great, but let's be honest: they haven't been anywhere near the panacea hoped for, and a lot of the pseudo-promises made around a return to normalcy haven't been kept. Instead, the goal posts keep changing.
Sounds like they've already decided what the findings are going to point at.
1. Vaccinate LOTS of people.
2. Accept that the hospitals are full of covid patients, so people who break a leg can't get a bed.
Option 2 isn't very desirable. It only took months to find some vaccines that make option 1 clearly better than option 2. (Some other vaccines failed, but you don't hear about those.)
I think we have to face the reality that vaccines won't stop this, and the only way out is after this burns through everyone. Vaccines can help reduce personal impact on severity but doesn't seem to be helping the hospital load problem.
https://qcovid.org/Calculation
And hospitalisation 1 in 4484.
By contrast your risk of death from anything at that age and gender is 1 in 1106 annually:
http://www.bandolier.org.uk/booth/Risk/dyingage.html
COVID risks are extremely concentrated to the obese, unhealthy, and elderly. It doesn't make sense to vaccinate the entirety of the population especially with a leaky vaccine.