Fertility Specialist at Sheba Medical Center Studying Impact of Pfizer COVID-19 Vaccine on Male Fertility

Fertility Specialist at Sheba Medical Center Studying Impact of Pfizer COVID-19 Vaccine on Male Fertility

Unfounded claims have attempted to correlate the mRNA-based vaccines rapidly developed to address COVID-19 infection and fertility in both men and women. According to Dr. Jigal Haas, a fertility expert operating out of Israel’s Sheba Medical Center, a new study was organized to investigate as there is little to no medical literature covering semen analysis parameters, for example, post mRNA-based COVID-19 vaccine, whether it be Moderna (mRNA-1273) or Pfizer/BioNTech (BNT162b2). However, there is no evidence that mRNA-based vaccines cause infertility.

Where does this concern originate?

The concern that mRNA-based vaccines could cause infertility stems from information that protein called syncytin-1 is found in the placenta in mammals. It shares similar genetic instruction with part of the SARS-CoV-2 spike protein. The hypothesis centers on the premise that because the vaccine triggers the body to produce antibodies against the coronaviruses’ spike protein that it would also trigger antibodies to syncytin-1 which could lead to infertility. However, there is absolutely no evidence to support this claim.

For example, neither mRNA-1273 (Moderna) nor BNT162b2 (Pfizer/BioNTech) contain syncytin-1 nor does the mRNA utilized in these vaccines encode for syncytin-1, according to a nice easy to understand description by the institute for Clinical Systems Improvement in Minnesota. They post that no data backs the theory that absolutely no antibodies formed as a consequence of mRNA-based vaccination target syncytin-1.

The Vaccine

Comprised of a lipid nanoparticle formulated nucleoside-modified RNA (modRNA) encoding the SARS-CoV-2 full length spike protein, the Pfizer vaccine was developed by the founders of Germany’s BioNTech and has been modified with two Proline mutations.

Pervasive Testing

Tens of thousands of people of course went through initial clinical testing and now tens of millions get inoculated with this mRNA-based vaccine product currently under emergency use authorization in the United States.  The testing shows that two 20 µg doses triggered a high amount of SARS-CoV-2 neutralizing antibody titers alongside high antigen specific CD8+ and Th1 type CD4+ cell response in subjects. The vaccine in clinical conditions demonstrated a 95% effective rate in preventing SARS-CoV-2 infection a week after the second jab with a positive safety profile base on analyses involving 2-month median follow up reports.

The Study

Now Dr. Haas and the study team will investigate the effect of the BNT162b2 COVID-19 vaccine on semen analysis parameters, focusing on 75 fertile men. This observational study (NCT04778033) started February according to an entry in Clinicaltrials.gov and is supposed to have met Estimated Primary Completion Date on April 10, 2021—May 1, 2021 is the final completion date target.

This study focuses only on men and they must be proven to be fertile by demonstrating that they previously impregnated their partner without the use of assisted reproduce technology, or previously had a normal sperm analysis exam using World Health Organization (WHO) 2010 criteria.  Participating males cannot be over the age of 45.

But what about the endpoints? Dr. Haas and team (including Dr. Dror M. Lifshitz) established ten primary endpoints for evaluation, including 1) semen concentration (10^6/ml) over a 1-2 month timeframe after the second COVID-19 response; 2) Sperm motility percentage 1-2 months after the second jab (sperm percentage with proper forward progression); 3) Amount of white blood cells (10v 6/ml) in semen; 4) Sperm morphology; 5) Sperm vitality; 6) Sperm liquefaction (macroscopic appearance); 7) Semen viscosity; 8) Semen color; 9) Semen PH and 10) Semen volume against 1-2 months after the second jab.

Lead Research/Investigator

Dr. Jigal Haas, Affiliated with Department of Obstetrics and Gynecology, Chaim Sheba Medical Center (Tel Hashomer), Ramat Gan, Israel

Call to ActionTrialSite has reached out to Dr. Haas and will monitor for results.


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