In this study from Israel, researchers found that sperm concentration reduces after Pfizer-BionTech vaccine, and then recovers after some months. Here are the results they posted with the study:

Repetitive measurements revealed −15.4% sperm concentration decrease on T2 (CI −25.5%–3.9%, p = 0.01) leading to total motile count 22.1% reduction (CI −35% – −6.6%, p = 0.007) compared to T0. Similarly, analysis of first semen sample only and samples’ mean per donor resulted in concentration and total motile count (TMC) reductions on T2 compared to T0 – median decline of 12 million/ml and 31.2 million motile spermatozoa, respectively (p = 0.02 and 0.002 respectively) on first sample evaluation and median decline of 9.5 × 106 and 27.3 million motile spermatozoa (p = 0.004 and 0.003, respectively) on samples’ mean examination. T3 evaluation demonstrated overall recovery without. Semen volume and sperm motility were not impaired.