Effect of BNT162b2 mRNA COVID-19 vaccine on sperm morphokinetics and DNA integrity: A prospective observational study in Japan

Objective: To assess whether the coronavirus disease 2019 (COVID-19) mRNA vaccine affects sperm morphokinetics using a computer-assisted semen analyzer and other semen parameters using a sperm chromatin structure assay. Methods: Healthy male volunteers in two Japanese clinics between May 2021 and December 2021 were prospectively analyzed. Participants donated sperm twice, two days apart, in the following phases: before vaccination, 2 weeks after the first vaccine dose, and 2, 4, and 12 weeks after the second dose. Basic sperm parameters, sperm motility characteristics, and the percentage of DNA-damaged sperm were compared among the different phases. Results: Ninety-six semen samples from ten volunteers, who were vaccinated with the BNT162b2 mRNA vaccine, were evaluated. There were no significant differences between any phases in basic semen findings and parameters of the sperm chromatin structure assays. Regarding sperm motion characteristics, the average linear velocity, beat-cross frequency, and sperm motility index significantly decreased after the second vaccine dose (P=0.018, P=0.003, and P=0.027, respectively), with no significant differences between any two phases by post-hoc pairwise comparisons. Conclusions: After COVID-19 mRNA vaccination, while sperm motion characteristics might fluctuate, no apparent deterioration of basic sperm parameters or sperm DNA integrity was observed. Given the adverse effects of COVID-19 on sperm, our findings suggest that there might be no reason to refrain from vaccination for healthy individuals.