Does the mRNA vaccine affect semen?


Excerpts from:


Free Access

Covid-19 vaccination BNT162b2 temporarily impairs semen concentration and total motile count among semen donors

Itai Gat, Alon Kedem, Michal Dviri, Ana Umanski, Matan Levi, Ariel Hourvitz, Micha Baum

First published: 17 June 2022



The research included 37 SD who supplied at least single semen sample prior (T0) and post- (either T1, T2 or T3) vaccination. SB #1 included 9 SD who supplied total 60 samples while SB # 2 and # 3 included 12 and 16 SD providing 78 samples each, resulting with total 216 samples. SD average age was 26.1 ± 4.2 years without significant difference between SBs (Table 1). While T0 samples were collected before vaccination (up to 2 samples per donor, total 51 samples), average collection intervals post-vaccination were 26.7 ± 10, 92.5 ± 13.4 and 174.8 ± 26.8 days post-vaccination date for T1, T2 and T3 (p < 0.0001, respectively, up to 3 samples per donor on each time frame).


Following rapid and successful pre-clinical and human trials, several vaccines have been developed by international partnerships including Astra Zeneca/Oxford University, Pfizer/BioNTech, Moderna.19 Over the past year, various studies supplied convincing data supporting vaccinations’ efficiency not only be reducing mortality rate but also in lessening in illness severity, hospital admissions resulting with overall improved outcome and prognosis.13, 20, 21 These results demonstrate historic scientific medical achievement. Opposed to that magnitude success, a parallel dramatic phenomenon of the fake news is spread over societies and countries. Content analysis determined that fake news could be divided into Health- and non-health-related types such as religious beliefs, politics, economy, prevention of the infection, the origin of the disease, conspiracy theories etc.22 World Health Organization’s Director-General declared the global ‘over-abundance’ of Covid-19 information an ‘infodemic’.23

One of the most concerning issues is the possible impact of vaccine on human reproduction.14 Previous reassuring publications were mainly based on single pre- and single-post-vaccination samples per participant.16, 17, 24, 25 Safrai et al. investigated pre and post-vaccination semen samples of 72 patients undergoing IVF treatments. Only two samples were included with average time of 71 days between first vaccination dose and post-vaccination sample.25 Lifshitz et al. conducted prospective study among fertile men with similar design including only 2 samples – single pre- and single post-vaccination – the later supplied on average of 37 days post-second vaccination dose.24 Therefore, both studies included only two semen samples with follow up equivalent to T1 in the current research yielding similar results but not relevant for the current concentration and TMC decline 3 months post-vaccination completion. Furthermore, Gonzales et al. and Barda et al. reported semen improvement post-vaccination16, 17 without convincing scientific rationale for their observations. The current study, composed of 37 SD and 216 semen samples over four time points, demonstrates selective temporary deterioration of sperm concentration 3 months after vaccination resulting with impaired TMC without alternations in volume and motility, followed by later recovery. We insisted on verifying our findings by diverse statistical analyses since semen samples are characterized by high within- and between-subjects variations.26 Hence, these results were not solely observed by repetitive analysis but also by using a single sample as well as samples’ mean per donor for each time frame. Therefore, the long-term impact of BNT162b2 vaccine seems safe. To the best of our knowledge, this is the first longitudinal research that continuously examined semen analysis after vaccination over 6 months – beyond the spermatogenesis period in human.

Almost 2 decades ago, Carlsen et al. characterized the detrimental impact of febrile illness on various stages of spermatogenesis.27 The COVID-19 vaccines can cause mild adverse effects after the first or second doses, including pain, redness or swelling at the site of vaccine shots, fever, fatigue, headache, etc.28 Therefore, rather than a direct effect on testicular cells (ex. via ACE receptor), we believe that systemic immune response is a more reasonable explanation for the temporary concentration decline. Interestingly, Mohamed Abdelhamid et al. have recently suggested that fever from SARS-CoV-2 virus infection induces a reversible negative effect on the semen parameters until one cycle (74 days) of spermatogenesis.29 The current study supports that notion not only regarding the febrile systemic response, which impairs spermatogenesis but also on the timing and duration of these alternations. Focusing on long-term follow up, Abdelhamid et al. emphasized illness-related testicular damage, which extends beyond patient’s recovery. Consequently, they suggested to add that adverse effect to the list of long-term post-COVID-19 syndromes.29, 30 On the contrary, our findings demonstrate long term recovery after vaccination.

The current study has several limitations. The most important is the focus on SD rather than the general population of patients with subfertility. However, since SD supplies semen on a regular base it enabled a longitudinal design over two post-vaccination time frames versus pre-vaccination baseline. Guo et al. have recently reported temporary decreased semen parameters (sperm concentration, sperm motility etc.) among 41 patients who recovered from Covid-19 compared to healthy controls 75 days after symptoms’ appearance. However, significant improvement was noted among 21 patients who supplied a second sample a month later,30 demonstrating the importance of continuous follow-up as performed in the current research. Another limitation is the retrospective design, although we assume its impact on our results and conclusions is small due to high overall similarity among all examined parameters.

In conclusion, in this longitudinal multicenter study, we found a selective temporary decline of sperm concentration and total motile count 3 months post-vaccination followed by recovery among SD. While on first look, these results may seem concerning, from a clinical perspective they confirm previous reports regarding vaccines’ overall safety and reliability despite minor short-term side effects. Since misinformation about health-related subjects represents a public health threat,23 our findings should support vaccinations programs. Further studies concentrating on different vaccines and populations (ex. subfertile patients) are urgently required.



Video misrepresents study on COVID-19 vaccines and male fertility

June 24, 2022

CLAIM: A new study shows that a second dose of a COVID-19 vaccine decreases sperm count and after a third shot “it’s almost unrecoverable.”

AP’S ASSESSMENT: Partly false. A new Israeli study did report a reduction in sperm count about three months after a second dose of Pfizer’s vaccine — but the effect was temporary and disappeared in subsequent samples. Experts say this is likely due to a fever, which can follow vaccination or infection and temporarily affect sperm production. The Israeli study did not examine the effects of a third dose.

THE FACTS: In a widely viewed video shared on Instagram this week, one man claims that “sperm count in men is declining at a rapid rate and it’s all because of the vaccine.”

“New studies have shown that after the second shot there’s a 22% decrease in sperm count and after the third shot, after the third booster, it’s almost unrecoverable,” he continues. “Almost half a billion men have been vaccinated. Now what is going to happen with society?”

A recent Israeli study in the journal Andrology did find that there was a temporary reduction in sperm count of about 22% among samples from donors three months after the second dose of Pfizer’s vaccine.

But an author of the study told The Associated Press the findings were not cause for alarm, and are typical of what’s seen with a fever.

“The observation we saw, which is characterized by ‘window’ of impairment 3 months after vaccination, is very similar to previously reported sperm decline after common febrile diseases (such as flu),” Dr. Itai Gat, of the Shamir Medical Center in Israel, said in an email.

The researchers found at six months that the reduction “disappeared,” Gat said. “We came to the conclusion that impairment is temporary and long term outcome remains good.”

Dr. Ranjith Ramasamy, director of male reproductive medicine and surgery at the University of Miami’s health system, who has separately researched the issue, told the AP the Israeli study was small but added interesting information to the field.

It “would be among the first to demonstrate that COVID-19 vaccines (specifically Pfizer) could lead to a decrease in sperm parameters in the short-term,” Ramasamy said in an email.

“Importantly, the authors note that unlike the actual SARS-CoV-2 virus that can cross the blood-testis barrier and impact the local testicular environment — these temporary decreases described in this study are most likely attributed to the fever some people experience with vaccination,” Ramasamy said.


Fact Check: Does Pfizer COVID Vaccine Lower Sperm Quality?

By Ed Browne On 6/22/22 at 11:54 AM EDT

On June 17, a study was published in the journal Andrology titled ‘COVID-19 vaccination BNT162b2 temporarily impairs semen concentration and total motile count among semen donors’.

The authors stressed that rather than being concerning, their results “confirm previous reports regarding vaccines’ overall safety and reliability despite minor short-term side effects.”

The study reads: “Since misinformation about health-related subjects represents a public health threat, our findings should support vaccination programs.”

It is also not the only study to investigate vaccines and sperm quality. One study, due to be published in The International Journal of Gynecology & Obstetrics next month and published online in February, suggested that vaccines have no ill effects on sperm quality, based on 898 samples from 33 men. These men’s sperm samples were tested once before their second Pfizer vaccine shot and once again at least 72 days after.

In fact, that study even suggested that total sperm count and total motile count increased after the second vaccine compared to before vaccination.

A June, 2021 study published in The Journal of the American Medical Association involving 45 men came to a similar conclusion, appearing to show that there were “no significant decreases in any sperm parameter” before and after two doses of either the Pfizer or Moderna vaccines, and also appeared to show an increase. The authors suggested this increase was “within normal individual variation and may be influenced by regression to the mean.”

Mostly False.

One study does indeed appear to show that a second vaccine dose coincided with a temporary decline in sperm count that later recovered, but it is not a conclusive study and multiple earlier studies had shown the opposite to be true. More research on this topic is needed.





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