Pfizer or Moderna vaccines against the new coronavirus are “safe for male reproduction” and do not have a negative impact on male fertility, according to a study prepared by the University of Miami (UM) and released on Thursday by the Journal of the American Medical Association (JAMA).

“We are the first to examine whether there is any impact of the COVID-19 vaccine on male fertility potential, and we did not find it,” scientist Ranjith Ramasamy, head of the study published Thursday, said in a virtual meeting.

The findings and the clinical study suggest that the Pfizer or Moderna vaccines did not produce adverse reproductive effects in the male participants who received the vaccine.

This “could have huge implications for reducing vaccinating hesitancy” on the part of people, according to Ramasamy, professor and director of the Reproductive Urology Program at the UM Miller School of Medicine.

The team of scientists did not study the effects of Johnson & Johnson’s single-dose COVID-19 vaccine.

Ramasamy explained in a virtual event that he and his team from Miller College examined 45 healthy male volunteers between the ages of 18 and 35 and evaluated sperm parameters before and after vaccinating them.


“None of the study participants showed any decrease in sperm parameters,” noted the lead author of the report.

The bottom line, Ramasamy added, is that “COVID-19 vaccines appear to be safe for male fertility.”

The volunteers, who had no fertility problems at the beginning of the study, provided a semen sample before receiving the first dose of the Pfizer or Moderna vaccine and gave another sample about 70 days after the second dose.

“This is the complete life cycle of the sperm and 70 days is enough time to see if the vaccine affects the parameters of the semen,” said Daniel C. González, a student at the aforementioned faculty and one of the participants in the preparation of the study.

“We measured semen volume, sperm concentration, and total amount of moving sperm and found that there were no decreases in any of the parameters compared to the baseline analysis,” González said.

Ramasamy’s team’s study shows that there is no evidence, either real or theoretical, that the vaccine against this disease causes infertility.

Researchers have found that antibodies continue to evolve over a period of 6 to 12 months.


Additionally, these scientific findings will serve to end “vaccine vacillation … a barrier to ending the COVID-19 pandemic.

“We believe that part of that hesitation is due to public opinion about whether the vaccine could negatively affect fertility,” something that is ruled out by this study, Ramasamy said.

The first rigorous clinical trials of the BNT162b2 mRNA (Pfizer) and mRNA-12732 (Moderna) vaccines that were allowed in this emergency situation by the US Food and Drug Administration (FDA), did not evaluate their possible “reproductive toxicity” , according to Ramasamy.

Therefore, despite the “high efficacy and few adverse events found in clinical trials,” only 56% of people in the United States wanted to receive the vaccine.

The study, which concluded on April 24, was carried out between December 17 and January 12, and the average age of the 45 volunteer participants was 28 years.

Other UM Miller School scientists involved in the study include Daniel E. Nassau, an expert in reproductive urology; Kajal Khodamoradi, professor of clinical research; Emad Ibrahim, Assistant Professor of Urology and Neurological Surgery; Ruben Blachman-Braun, urologist, and Jesse Ory, expert in reproductive urology.

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