The effect of BNT162b2 mRNA COVID-19 vaccine on human semen

Scientists from Italy have recently analyzed the effect of the mRNA-based coronavirus disease 2019 (COVID-19) vaccine on the semen quality of adult men. No significant difference in sperm quality and seminal plasma parameters (oxidative stress, inflammation, and electrolyte level) has been observed after vaccination. The study has been published in the journal Andrology.

Study: 4BNT162b2 mRNA Covid-19 Vaccine and semen: what do we know? Image Credit: vchal/Shutterstock
Study: 4BNT162b2 mRNA Covid-19 Vaccine and semen: what do we know? Image Credit: vchal/Shutterstock


Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the causative pathogen of the COVID-19 pandemic, is a deadly member of the human Betacoronavirus family. The virus is known to induce a wide variety of symptoms in infected persons, ranging from mild respiratory symptoms to severe pneumonia, respiratory failure, and death. Apart from infecting the respiratory tract, the virus can potentially impair the functions of other organs, including the heart, liver, gastrointestinal tract, kidney, and brain.

A handful of studies have indicated that people infected with SARS-CoV-2 may develop testicular abnormalities, including structural alteration in testicular cells, loss of integrity of the basement membrane and seminiferous tubules, and infiltration of proinflammatory mediators. However, no comprehensive data is currently available to understand the impact of COVID-19 vaccines on reproductive functions.

In the current study, the scientists have assessed the effects of mRNA-based COVID-19 vaccine BNT162b2 (Pfizer/BioNTech) on human semen. 

Study design

The study was conducted on a total of 47 adult men who had received the two-dose regimen of Pfizer vaccine between February and July 2021. The semen samples were collected from the participants before the administration of the first vaccine dose and 70 days after the second dose.

All semen samples were analyzed to measure sperm concentration, motility, and morphology. In addition, the concentrations of reactive oxygen metabolites, electrolytes, and interleukin 6 (IL-6) were determined using seminal plasma samples.

Important observations

Among all enrolled participants, 10% reported smoking moderately, and 38% reported consuming alcohol socially. None of the participants reported systemic side effects, such as fever, allergy, or lymph node swelling.

No significant changes in semen volume, sperm concentration, motility, and morphology were observed among participants after COVID-19 vaccination compared to before vaccination. 

A separate set of experiments was conducted on male participants who presented with low sperm count or reduced sperm motility. In these participants, no significant differences in sperm parameters were observed after vaccination. However, the sperm parameters showed an improving trend in these participants.

Alike sperm parameters, no significant changes in electrolytes (calcium, chlorine, potassium, magnesium, and sodium), reactive oxygen metabolites, and IL-6 levels were observed among participants after vaccination.

Furthermore, no significant correlations were observed between tested sperm parameters and electrolytes and reactive oxygen metabolites, and IL-6.

Study significance

The study findings reveal that the mRNA-based COVID-19 vaccine (Pfizer) does not have any negative impact on sperm quality. Moreover, the vaccine does not alter the levels of electrolytes (an indicator of good cell membrane activity), reactive oxygen metabolites (an indication of oxidative stress), and IL-6 (an indicator of inflammation).

Overall, the study highlights that the COVID-19 vaccine is safe for use among men. However, the study includes only a small number of men with poor sperm quality who are highly susceptible to deteriorating sperm parameters. Moreover, since the study participants belong to a specific population, the findings cannot be generalized to the global population.

Journal reference:
Dr. Sanchari Sinha Dutta

Written by

Dr. Sanchari Sinha Dutta

Dr. Sanchari Sinha Dutta is a science communicator who believes in spreading the power of science in every corner of the world. She has a Bachelor of Science (B.Sc.) degree and a Master's of Science (M.Sc.) in biology and human physiology. Following her Master's degree, Sanchari went on to study a Ph.D. in human physiology. She has authored more than 10 original research articles, all of which have been published in world renowned international journals.


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  1. Phil Asplin Phil Asplin Canada says:

    People arnt concerned it affects sperm mobility. Were concerned it can transpose the spike protein into the sperm or egg's DNA from reverse transcribing of RNA into DNA like it's already shown to happen in some cases with other human sells tested in vitro(in a dish and not in a person) so that study is far more important to carry out.

  2. Laurence Renshaw Laurence Renshaw Malaysia says:

    Any study showing nothing is dull, but never mind.
    This study, showing no immediately obvious ill effects on sperm, may be mildly positive, but the conclusions drawn are laughable.
    Even if it proved that there are no ill effects on sperm (it doesn't, but I won't quibble about that), that does not show that the vaccines are perfectly safe for young men.
    Scientific/medical journalism requires some logical thinking.

  3. Thomas Roundtree Thomas Roundtree United States says:

    So what is the population it was most occurring in?

  4. Robert Schramm Robert Schramm United States says:

    47?  Vaccine has been given to millions and they tested 47?  This doesn't even get on the scale of significance. What I can't believe is that there is no criticism in this article of the study.  Let's all forget that science is about critical thinking, reasoning and skepticism.  Challenging a study like this is at the very least the appropriate thing to do.

  5. Mary Oleary Mary Oleary New Zealand says:

    Seriously, how do these articles get published? Millions or billions have had these pseudo vaccines. In the world of research, 100 is a minimum sample size. I would expect that number to increase proportionately relative to the number of subjects...49 people is a joke and not even vaguely relevant. Shame on you for publishing this lame survey without sufficient numbers - not to mention demographic breakdown by age as a bare minimum. Honestly. I can't even believe this is legal to put into print. Shame on the perpetrators - part of the problem of the perpetual reign of fake news with zero validity. I sincerely hope this article is withdrawn as it is meaningless and a slight on both journalism and medical research.

  6. Cali Neilson Cali Neilson United States says:

    This study only included a small number of men who didn't have any systemic effects from the covid vaccines in the first place?? Sounds like they picked particular men to study that would likely give them the conclusion that they WANTED. Also, this does not at all prove that the sperm was not affected.

  7. Marivic Villa, MD Marivic Villa, MD United States says:

    This study is a BIG JOKE. I see men all the time with Testosterone dropping from 700+ down to below 100 after the shot. Do a baseline then do determination in few months / 6 months/ 1 year
    Forget about semen and sperm. Look at your Testosterone blood levels. You don't have T “it aint happening”!!!!!

The opinions expressed here are the views of the writer and do not necessarily reflect the views and opinions of News Medical.
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