The main aim of the study was to assess the contagiousness of sperm and its influence on fertility after recovery from COVID-19 infection.
Sperm quality was assessed using the World Health Organization criteria. All DNA damage to sperm cells was assessed by quantifying the DNA fragmentation index and the high-density stainability. Finally, antibodies against SARS-CoV2 spike-1 antigen, nuclear and S1-receptor binding domain were measured by Elisa and chemilumenscent microparticle immunoassays, respectively.
However, mean progressive motility was reduced in 60% of men tested shortly (<1 month) after COVID-19 infection, 37% of men tested 1 to 2 months after COVID-19 infection, and 28% of men tested >2 months after COVID-19 infection.
The study findings however alarmingly showed that mean sperm count was reduced in 37% of men tested shortly (<1 month) after COVID-19 infection, 29% of men tested 1 to 2 months after COVID-19 infection, and 6% of men tested >2 months after COVID-19 infection.
Interestingly the severity of COVID-19 infection and the presence of fever were not correlated with sperm characteristics. Even men who were asymptomatic or only had mild conditions still suffered low sperm and motility rates.
However, there were strong correlations between sperm abnormalities and the titers of SARS-CoV-2 IgG antibody against spike 1 and the receptor- binding domain of spike 1, but not against nucleotide, in serum. High levels of anti-sperm antibodies developed in three men (2.5%).
The study findings also showed that semen is not infectious with SARS-CoV-2 at 1 week or more after COVID-19 infection (mean, 53 days). However, couples with a desire for pregnancy should be warned that sperm quality after COVID-19 infection can be suboptimal.
The estimated recovery time is 3 months, but further follow-up studies are under way to confirm this and to determine if permanent damage occurred in a minority of men.
The study findings were published in the peer reviewed journal: Fertility A
nd Sterility (Elsevier).
SARS-CoV-2 uses the ACE-2 receptor to infiltrate human cells. These receptors are found in the respiratory tract where the infection mostly occurs, but also in the male reproductive tract (2). In analogy with other RNA viruses that cause viremia and cross the blood–testis barrier, we hypothesized that the presence of SARS-CoV-2 RNA in human semen could lead to transfer of this virus through sexual intercourse.
We validated a PCR test (SpermCOVID test) especially to test this hypothesis. However, we could not detect any SARS-CoV-2 RNA during convalescence after documented COVID-19 infection from testing an average 53 days after a positive SARS-CoV-2 nasopharyngeal PCR test. Tests were negative as late as 181 days and as early as 6 days after positive testing.
This is an important finding, since whether SARS-CoV-2 could be transmitted sexually after convalescence from COVID-19 infection was still unclear. These findings are similar to the findings of Pan et al., who also could not detect any SARS-CoV-2 RNA in human semen at an average of 31 days after acute COVID-19 infection (15), and of Holtmann et al. (2), who reported negative sperm RNA results in 28 men tested 8 to 54 days after (Supplemental Figure 1) COVID-19 infection.
Our data confirm the findings of a smaller trial by Holtmann et al. (2), which also detected no SARS-CoV-2 RNA in human semen obtained 8 to 54 days after the absence of symptoms, a period similar to our short and medium-long postinfection lapse time groups. In one study in which SARS-CoV-2 RNA was detected in 6 of 32 semen samples, 4 of these 6 participants suffered from a severe, active COVID-19 infection while the sperm was being tested (5).
In concordance with this, viral SARS-CoV-2 RNA was also encountered in testicular cells and Leydig cells of two men who died from COVID-19 (16). According to our and Holtmann’s data, however, SARS-CoV-2 RNA rapidly disappears from the testes after recovery from COVID-19 infection in all men (2). Therefore, it is conceivable that the blood–testis barrier can be crossed by the SARS-CoV-2 virus during the acute phase of the disease, but not after convalescence (21 days).
Still, despite the absence of detection of SARS-CoV-2 RNA in semen, we found evidence of severely decreased quality parameters after convalescence from SARS-CoV-2 infection. The negative impact of COVID-19 on sperm quality mainly affected sperm concentration, motility, and DFI, whereas the correlation with abnormal morphology was less clear. These results confirmed data from Holtmann et al. (2), who also found mainly decreased concentration and motility of spermatozoa in men who had had moderate COVID-19 infection (2).
In that study, such abnormalities were not found in men with mild COVID-19 infection or in COVID-19-negative controls. In contrast, in our study we found no differences in sperm quality parameters between patients who had to be admitted to the hospital and those who could stay home with COVID-19 infection and no correlations between sperm quality parameters and total COVID-19 symptom score.
The decrease in sperm quality parameters was greatest in men who were tested soon after recovery from COVID-19, less in men tested after 1 month, and least in men tested after 2 months or more. This could lead to the conclusion that the temporary sperm abnormalities seen during acute COVID-19 infection could be due to fever, since hyperthermia is known to have this effect (17).
During other viral infections, such as influenza, sperm motility can be linked to the severity of fever, with a maximal decrease of motility seen at day 37 and normalization of motility by day 54 after fever (18). However, in our study, the presence and severity of fever and symptom score during COVID-19 disease were not correlated with sperm quality parameters, indicating that other mechanisms than fever linked to COVID-19 infection could be involved in the pathogenesis of sperm damage.
To assess these other mechanisms in further detail, we tested the strength of the immune response by measuring antispike (sIgG-S), antinucleotide (sIgG-N), and neutralizing anti-S1-RBD antibodies (sIgG-RBD) against SARS-CoV-2 in serum, and compared these findings with sperm quality measures, as well as with the presence of IgG and IgA antisperm antibodies on spermatozoa (MAR test). A very strong correlation was found between the titer of anti-SARS-CoV-2- S1 (sIgG-S) and -RBD (sIgG-RBD) serum antibodies and all sperm quality parameters, including increased DFI and HDS.
The latter two markers of DNA damage are strongly linked to reduced fertility, independent of the WHO sperm quality parameters, and were associated with a dramatic reduction in pregnancy success in patients treated with intrauterine insemination for infertility, when they were inseminated with human papillomavirus (HPV)-infected sperm (19).
Whereas in the case of HPV infection, the pathogenetic mechanism is thought to be linked to direct binding of HPV virions to the syndecan-1 receptor localized on the head area of the spermatozoan, inducing sperm DNA damage, the most likely explanation of reduced sperm function after COVID-19 infection is due to the induction of cytokines after IgA secretion.
The attachment of both IgA and IgG ASA to the tail of the spermatozoa points to a common epitope for both antibody types against SARS-CoV-2 virus. This could explain the strong association between both WHO sperm quality parameters and markers of DNA damage in sperm with the antibody titers after COVID-19 infection.
We also demonstrated that twice as many convalescent COVID-19 participants had IgA ASA in their semen than IgG ASA (P<.0001). This is not unexpected, since IgA is the principal antibody secreted as a first-line defense by mucosal surfaces of the respiratory, gastrointestinal, and genitourinary tracts on a viral or bacterial challenge (20). In contrast to the local production of IgA, IgG diffuses from the blood to the semen (21), and IgG must find its way into external secretions via receptor-independent paracellular diffusion, receptor-mediated transepithelial transport, and fluid-phase endocytosis, all of which are different from the mechanism by which IgA and IgM enter secretions (22).
Because we measured ASA an average of 54 days after SARS-CoV-2 infection, the short-term impact of the measured IgA ASA on fertility seems low, with only one participant having more than 40% of motile spermatozoa affected by IgA ASA. In the long-term, follow-up will have to show what happens to the majority of subjects in whom we detected IgA ASA, since augmented or aberrant presence of IgA immune complexes can result in excessive neutrophil activation, potentially leading to chronic tissue damage in multiple inflammatory, or even autoimmune, diseases (23).
Therefore, sperm IgA ASA may have an impact on fertility in the longer term, and long-term follow-up is warranted. For that reason, we prolonged the follow-up time for our study participants and will report on the long-term results of sperm quality and immune reactions in a separate article. ASA can recognize spermatic surface antigens that can interfere with sperm motility and transport through the female reproductive tract and inhibit capacitation and acrosome reaction (3), mediate the release of cytokines that affect sperm function, and impair sperm–cervical mucus interaction (24), induce sperm cytotoxicity, increase sperm phagocytosis, and inhibit embryo development and implantation.
As a result, natural pregnancy rates decrease when ASA are present (24). The strong IgG ASA positivity against the entire spermatozoan soon after SARS-CoV-2 infection suggests there may have been a breach of the blood–testis barrier during the acute phase of COVID-19. This is in agreement with previous studies on a limited number of patients who were in the acute phase of COVID-19 at the moment of testing, who showed SARS-CoV-2 RT-PCR positivity in the semen (5).
The strong points of this study are the unbiased group of patients (not just men presenting with infertility problems), the large study group, the unequivocal proof of the evidence and timing of COVID-19 infection, and the possibility of studying both contagiousness and sperm quality parameters in association with disease severity and SARS-CoV-2 antibody production. Additionally, differences in the COVID-19 variants [the so-called British (α), South-African (β), Brazilian (γ), and Indian (δ) variants] had no effect on our outcome data, since our inclusion period occurred during the first and second COVID-19 waves, when only the original Chinese/Huwan variant was prevalent.
A weakness of our study is that we had no comparative sperm samples from the participants before they contracted COVID-19, nor were we able to include samples from matched control men without COVID-19, since the only comparison samples at our disposal were from infertility patients or from patients who were in general younger than our study patients. Still, by introducing a follow-up period of 6 months as an amendment to our study, we will be able to provide specific detailed information on the mechanisms of recovery of sperm quality over time.