No significant differences were found in a study assessing the effect of the mRNA COVID-19 vaccines on key measures of male fertility.

Forty-five male participants, aged between 18 and 35, took part in a study which compared sperm samples of participants before and after administration of two COVID-19 vaccine doses. Each participant provided a sperm sample before, and approximately 70 days after, receiving two doses of either the Pfizer or Moderna COVID-19 vaccine.

Lead author of the study Daniel Gonzalez from the University of Miami Miller School of Medicine, Florida said: 'This is the full life cycle of sperm and 70 days is sufficient time to see if the vaccine impacts semen parameters'.

When the COVID-19 vaccines were evaluated in clinical trials, their effects on fertility and reproduction were not studied.

Dr Ranjith Ramasamy, director of the Miller School's Reproductive Urology Programme, was the first to demonstrate that SARS-Cov-2, the virus which leads to COVID-19, can affect male fertility. He said 'we are now the first to examine if there is any impact of the COVID vaccine on male fertility potential, which we did not find.'

In this study, published as a research letter in JAMA, Dr Ramasamy and colleagues investigated measures of fertility, including semen volume, sperm concentration, sperm motility, and total motile sperm count. They concluded that no significant difference was found for any measure across the cohort.

According to a report led by Imperial College London's Institute of Global Health Innovation, the top reasons for vaccine refusal are 'concerns about side effects' and 'concerns that there has not been enough testing of vaccines'. Furthermore, the effect on fertility is also often reported as a concern among those worried about potential side effects of the COVID-19 vaccine.

Professor Allan Pacey, professor of andrology at the University of Sheffield who was not involved in the study, told CNN: 'I hope this provides some reassurance to any men who may be concerned about their fertility if they accept one of these types of vaccines.' 

The study did not test COVID-19 vaccines not based on mRNA platforms, such as the AstraZeneca or Johnson & Johnson vaccine. 'However, we think the mechanism of how these vaccines work is all fairly similar despite different genetic material, so based on biology, we don't think there should be anything different with the other two vaccines,' explained Dr Ramasamy.

The authors note the study limitations, including the small number of participants, and the age restriction to young men. Professor Pacey concluded: 'Additional larger studies with men of different ages are needed to affirm the study's results.'

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Reproduced from BioNews with permission, a web- and email-based source of news, information and comment on assisted reproduction and human genetics, published by Progress Educational Trust.