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COVID-19 mRNA vaccines do not affect sperm count

21 June 2021
Appeared in BioNews 1100

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 (see BioNews 1071). 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.'

Pfizer and Moderna COVID-19 vaccines do NOT lower sperm counts and could actually increase semen levels, study finds
Daily Mail |  17 June 2021
Pfizer, Moderna vaccines do no harm to male fertility: study
HealthDay |  17 June 2021
Sperm count not harmed by Covid-19 vaccine, study says
CNN |  17 June 2021
Sperm Parameters Before and After COVID-19 mRNA Vaccination
Journal of the American Medical Association |  17 June 2021
University of Miami Miller School study shows COVID-19 mRNA vaccines do not impact male fertility
University of Miami Miller School of Medicine |  17 June 2021
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