Commentary on “The effect of COVID-19 vaccines on sperm parameters: a systematic review and meta-analysis”

The COVID-19 pandemic caused by the strain of coronavirus – severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) was first reported in Wuhan (China) in December 2019, and then, it has rapidly spread around the world.1 According to the World Health Organization data, officially, it has been noted 628 346 704 cumulative cases of infection and 6 573 968 cumulative cases of death (data as of November 4, 2022, https://covid19.who.int/table). It should be highlighted that COVID-19 is a threat not only due to respiratory system failure and the risk of death but also because the infection is associated with andrological consequences, which is particularly important in the era of the growing global infertility issue.

Coronaviruses have been found to invade target cells through the angiotensin-converting enzyme 2 (ACE2) receptor, which can be found, for example, in the testes. Briefly, the proposed hypotheses indicate that the virus can invade the testes through the ACE2 receptors and activate inflammatory response in the tissue that influences spermatogenesis.2,3 It was noted that men who recovered from COVID-19 had significantly reduced total sperm count, sperm concentration, motility, and vitality and increased number of abnormal sperm forms in the ejaculate.3,4

The humanitarian and economic effects of the COVID-19 pandemic have become a trigger for the development of a vaccine against SARS-CoV-2. One of the milestones in this field was the sequencing of the viral genome. In March 2020, the prototypes of the first vaccine were ready to start clinical trials on humans. Scientists have used a variety of approaches to maximize the chances of a safe and effective COVID-19 vaccine being developed quickly. One of them was novel-like mRNA vaccines. In mRNA vaccines, a ready-made antigen is not provided, but a precise recipe for its preparation in the form of mRNA encoding information about a protein that functions as an antigen. The protein that acts as an antigen in COVID-19 vaccines is the SARS-CoV-2 spike (S) protein.5 However, the introduction of a new type of vaccine has raised concerns among clinicians, scientists, and the general public about harmful effects after vaccination, for example, in the male reproductive system.6,7 Hence, there is a need to conduct reliable and independent scientific research answering the question about the safety of mRNA vaccines and side effects related to male reproductive health.

One of the publications dealing with this challenge is the meta-analysis performed by Ma et al.8 The authors selected seven screened studies based on records from PubMed and Embase Databases. Data from the studies were used for statistically comparing semen variables before and after COVID-19 vaccination: six studies for comparison of total sperm motility, semen volume, and sperm concentration; three studies for comparison of sperm morphology; and two studies for comparison of total sperm count. Based on the performed analysis, Ma et al.8 demonstrated that vaccine injection has no significant negative effect on the ability of seminiferous epithelium to produce sperm cells – there were no significant differences in total sperm count and sperm concentration before and after vaccination. Moreover, the significant decrease in semen volume, sperm morphology, and motility also was not observed. This meta-analysis revealed no discernible changes in semen quality between the pre- and post-COVID-19 vaccination, which is an argument confirming the safety of the mRNA vaccines. On the other hand, Ma et al.8 rightly underlined the limitations of the research. First, basic semen parameters only partially reflect the ability of spermatozoa to fertilize. Second, only seven studies were included in the meta-analysis. Therefore, further studies on the long-term side effects of the COVID-19 vaccination are needed and attention should be focused not only on basic sperm parameters but also on advanced sperm parameters, like changes in sperm DNA quality and integrity as well as the male ability to become a father.

Summarizing, it is an important publication that objectively addresses concerns about male reproductive health. Based on the presented results, both clinicians and patients can resolve doubts about the side effects of the mRNA vaccine on spermatogenesis.

COMPETING INTERESTS

Both authors declare no competing interests.