Background: Based on available data on male fertility adverse effects after COVID-19 injections, we draw the reader´s attention to open questions and undeniable risks of the new RNA-based vaccine technology.

Methods: Review and reanalysis of published data on pre- and post-injection semen analyses. Evaluation of UK Yellow Card and US VAERS databases for male fertility adverse effects and of the German deStatis database for monthly live birth rates after start of the governmental vaccination program.

Results: The deStatis database demonstrates a time shift of exactly nine months between the start of the governmental vaccination campaign (April 2021) and an abrupt decline in live births (January 2022). Frequency of male fertility adverse effects is approx. 100 times lower than that of female fertility. Remarkably, report numbers per one million doses are similar between AstraZeneca and BionTech/Pfizer, but significantly increased for Moderna despite overall numbers of administered doses are smaller than that of the other two manufacturers. Both increase in and correlation between erectile dysfunction and heart failure could be demonstrated. Review and reanalysis of published data on pre- and post-injection semen analyses identified a number of limitations of the currently available studies.

Conclusion: There remain still far more questions than answers. Due to the principle “primum non nocere,” any new medical therapy must be banned until harmlessness beyond doubt has been proven. Most importantly, it must be realized that the active ingredient of RNA-based vaccines is not simply mRNA promoting the synthesis of a nota bene viral specific protein, but modRNA specifically designed for longevity and encapsulated in LNPs to bypass biological barriers and get access to all cells, possibly also germ cells. As mRNA is involved in regulation of gene expression, cells have mechanisms at hand to silence mRNA species not required, however, theses protective mechanisms will not work with modRNA.