This prospective study at the University of Miami, US, assessed sperm parameters (sperm count) before and after COVID-19 vaccine administration (Pfizer and Moderna vaccines). 45 men gave sperm samples before receiving the first dose and approximately 70 days after receiving the second dose. They had median age of 28 years, no underlying fertility issues, and were negative for COVID-19 infection or symptoms. The results showed that median sperm concentration, semen volume and sperm modality significantly increased after their second vaccine dose. The study authors noted that this increase was most likely associated with the longer abstinence period before the second sample. There were no significant decreases in sperm parameter in any of the men sampled. The authors noted that because there is no live virus in the vaccine, it was unlikely that the vaccine would have had an effect on sperm parameters. This study may help to address vaccine hesitancy associated with reproductive toxicity after decreases in sperm parameters were associated with SARS-CoV-2 infection.