According to a study published in the journal JAMA, Pfizer and Moderna COVID-19 vaccines do not appear to harm male fertility. 

The study noted that the levels of sperm in participants continued to be at healthy levels after receipt of two doses of the mRNA vaccines. It included 45 healthy male volunteers, 18 to 50 years of age, scheduled for mRNA COVID-19 vaccination. They were evaluated to ensure that they had no underlying fertility problems. A semen sample was obtained after two to seven days of abstinence, before receiving the first vaccine dose and about 70 days following the second dose. Investigators noted no significant reduction in any of the sperm parameters in the study participants. Sperm concentration and total motile sperm count at study initiation were 26 million/mL and 36 million, respectively; following the second vaccine dose, the corresponding values increased to 30 million/mL and 44 million, respectively… (NDTV – PTI, June 18, 2021)