Sperm count and quality did not drop in healthy young men after receiving a first or second dose of the Pfizer or Moderna vaccine, according to a new study published Thursday in JAMA. "We now have evidence that should reassure you that the risk of immunization compromising your sperm count is extremely low," said Dr. David Cohen, co-medical director of the Institute for Human Reproduction in Chicago, who was not involved in the study. Cohen was the co-author of a systematic review that found the novel coronavirus is not sexually transmitted. "This is reassuring data which suggests that sperm quality is not significantly altered by receiving two doses of one of the new mRNA vaccines for COVID-19," said Allan Pacey, professor of andrology at the University of Sheffield in the UK, who also was not involved in the study.