Preclinical (animal) data is used for the assessment on female fertility, and more generally on organ toxicity including testicular.
For example, the Pfizer vaccine on female fertility:
"Lack of effects on female fertility and prenatal and postnatal offspring development in rats with BNT162b2, a mRNA-based COVID-19 vaccine" (my bold)
BNT162b2 is a vaccine developed to prevent coronavirus disease 2019 (COVID-19). BNT162b2 is a lipid nanoparticle formulated nucleoside-modified messenger RNA (mRNA) encoding the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) spike ...
www.ncbi.nlm.nih.gov
Summary of the nonclinical data here.
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