1. Introduction

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is the cause of coronavirus disease 19 (COVID-19) that started in Wuhan, China, in December 2019, to become a pandemic causing a total of 778 million cases and 7 million deaths worldwide up to June 2025 [1].

Concerns about male sexual health and COVID-19 have arisen due to the binding of SARS-CoV-2 to the host cells which relies on an angiotensin-converting enzyme 2 (ACE-2), expressed by cells of several human tissues including the testis, and the subsequent entry into the cells through the priming of the viral spike protein regulated by Transmembrane Serine Protease 2 (TMPRSS-2), whose expression is modulated by androgens [2]. In fact, the entrance of SARS-CoV-2 in Leydig and Sertoli cells of the testis was thought to potentially deteriorate steroidogenesis and spermatogenesis leading to fertility problems, hypogonadism, and erectile dysfunction [3]. Despite initial reports suggesting otherwise [4], most authors have reported that SARS-CoV-2 does not appear to be detectable in the semen of COVID-19-infected subjects [5]. However, a temporary alteration in testicular function, both in terms of spermatogenesis [6] and hormone production [7], has been demonstrated. Long term COVID has also been associated with erectile disfunction mainly through vascular and psychological alterations [8, 9].

To face the pandemic, a number of vaccines were tested and marketed worldwide. From December 2020, with the emergency use authorization by the Food and Drug Administration (FDA), the first mRNA vaccines (BNT162b2 and mRNA-1273, by Pfizer-BioNTech and Moderna, respectively) to target the SARS-CoV-2 Spike protein became available. According to the initial clinical trials, the mRNA-based vaccines demonstrated 94–95% efficacy in preventing symptomatic COVID-19 after a two-dose immunization regimen, but with a significant decline in antibody levels after about 6 months, requiring booster doses to ensure effective and prolonged immune response [10]. The efficacy and safety of COVID-19 vaccines are supported by several articles [11] and confirmed by a recent meta-analysis of controlled and randomized clinical trials (RCTs), with the most common side effects being injection site discomfort, fever, fatigue, and headache (54.5% of subjects) [12]. Nonetheless, attitudes toward COVID-19 vaccines varied greatly among the population, with hesitancy and opposition mainly due to safety concerns and a perceived lack of effectiveness, as well as a distrust of vaccine manufacturers and public health authorities [11]. The hesitation and mistrust towards vaccination was not only evident in the less educated population [13], but also in a certain section of people belonging to the health sector [14, 15]. According to the latest World Health Organization (WHO) reports, 13.64 billion vaccine doses have been administrated worldwide so far, with 67% of the global population completing the primary vaccination series and 32% receiving at least one booster dose up to 31 December 2023 [1].

Among the health concerns related to mass vaccination, the effects on fertility were found to be particularly important, especially in the younger population. For example, misinformation on social media led young women to think that COVID-19 vaccines could cause sterility [16]. In an on-line survey of 914 unvaccinated U.S. subjects (about half of whom were male), Diaz et al. [17] reported that 41% of subjects responded “Yes” and 38% “Unsure” to the question “Do you believe COVID-19 vaccines can negatively impact fertility and/or reproductive health”, identifying fertility as the main concern for vaccine hesitancy in this category of population.

The present narrative review, therefore, aims to discuss the available evidence on the possible effect of COVID-19 vaccines on male sexual function, to provide an objective view of the topic and highlight areas of criticality in our current knowledge.

2. Methods

A narrative review was conducted through an extensive search for literature on PubMed between February and June 2025. The following research terms were used in various combinations: “Vaccines”, “COVID-19”, “SARS-CoV-2”, “fertility”, “semen parameters”, “sperm parameters”, “advanced semen parameters”, “advanced sperm parameters”, “erectile dysfunction”, “testosterone”, “hypogonadism”, “sex hormones”. Papers were considered eligible if their topic was the effects of COVID-19 and/or COVID-19 vaccination on male fertility, classic semen parameters, advanced semen parameters, erectile function and/or testosterone levels. The following criteria were used for exclusion: animal studies and scientific articles not published in English. Three reviewers (AC, NdM and GS) independently evaluated the title, abstract, and full text of each potentially relevant manuscript for eligibility. Any discrepancies were resolved by discussion.

3. COVID-19 vaccination and classic seminal parameters

In the early phase of the pandemic emergency, the observation that SARS-CoV-2 was detectable in semen of COVID-19 infected subjects [4] suggested a trophism of COVID-19 for the testis with a possible direct contact between the virus and the germ cell during the infection. However, these findings were not confirmed in subsequent studies [18, 19, 20, 21] even if many studies reported alterations in seminal parameters after COVID-19, probably resulting from the inflammatory context favoured by the infectious event [6, 22, 23]. In further support of this hypothesis, more significant alterations in seminal parameters were found in patients who developed a fever following infection than in asymptomatic patients [24].

Considering the negative effects of COVID-19 on spermatic function, concerns arose also regarding the possible effects of COVID-19 vaccination on male fertility. These were added to the worries of the public opinion on the safety of the vaccine, which had been developed in an emergency setting with reduced timelines compared with what is required in regular trials [25]. Many studies evaluated the effects of COVID-19 vaccination on spermatogenesis mainly considering sperm parameters as a surrogate marker of male fertility (Table 1, Ref. [26, 27, 28, 29, 30, 31]). The majority of papers did not show significant negative effects of the vaccine on semen parameters [32, 33, 34, 35, 36, 37, 38, 39, 40]. In particular, in the study by Dong et al. [37], four groups of patients were evaluated: 168 unvaccinated, 8 one-dose vaccinated, 183 fully vaccinated, and 160 vaccinated with booster dose. No significant difference in classic seminal parameters was found between the vaccinated and unvaccinated groups [37]. Similarly, in the study by Huang et al. [38], semen parameters measured before and after inactivated SARS-CoV-2 vaccination in 128 men did not show any significant difference. In contrast, some studies reported a negative effect of vaccines on semen parameters. Indeed, Gat et al. [41] conducted a study on 37 sperm donors and found a decrease in sperm concentration and total motility count (TMC) 3 months after COVID-19 vaccination with BNT162b2, but a full recovery was then observed in subsequent follow up evaluations. Abd et al. [42] described a statistically significant reduction in total sperm motility and progressive motility after vaccination, but these parameters remained within the normal range. Taken together, these data seem to suggest that the observed sperm quality impairment was transitory and not clinically relevant.

Despite the evidence leaning more towards the absence of a negative effect of vaccination on male fertility, the global impact of the issue has led to copious literature being examined and synthesised by multiple systematic-reviews and meta-analyses. In 2022, a meta-analysis of Huang et al. [26] evaluated twelve cohort studies and involved a total of 914 participants. The vaccinated subjects did not show any significant differences regarding semen volume, sperm concentration, total sperm motility, progressive sperm motility, total sperm count, total motile sperm count, total progressively motile sperm count, and sperm morphology in comparison with the unvaccinated group [26]. In the same year, a meta-analysis by Zaçe et al. [27] evaluated 29 studies (14 pre-post vaccination studies and 15 cohort studies) to evaluate the effects of the vaccine on sperm quality and fertility rates in women who underwent in vitro fertilisation (IVF). Fifteen studies were conducted on females, 11 on males, and 3 on both components of a couple. No significant differences were found regarding sperm concentration, volume, and motility. The effects on semen parameters were not influenced by the type of vaccine used. Biochemical and clinical pregnancy rates did not show any significant differences between the vaccinated and unvaccinated groups [27]. In 2023, Ma et al. [28] conducted another systematic review and meta-analysis. Once again, no significant differences were found regarding total sperm motility, semen volume, sperm concentration, morphological change, and total sperm count in the pre- and post-vaccination studies analysed. Inactivated or messenger RNA (mRNA) COVID-19 vaccinations did not show any different effects on semen parameters [28]. In addition, a systematic review by Li et al. [29] reported data from 24 pre- and post-vaccination cohort studies respectively on: males affected by infertility undergoing assisted reproduction techniques (ART), healthy volunteer sperm donors, and males affected by type 2 diabetes without other relevant diseases. The included studies reported different sperm parameters: 9 evaluated total sperm count, 23 evaluated sperm concentration, 7 evaluated sperm morphology, 19 evaluated total sperm motility, 17 evaluated progressive sperm motility, and 11 evaluated total motile sperm count (TMSC). The results of this systematic review confirmed the absence of significant alterations in semen parameters after vaccination [29].

Regarding the most recent evidence, a large retrospective study on 6007 couples undergoing IVF evaluated clinical pregnancy rates and semen parameters according to the vaccination status of males, females, and couples (vaccinated male with unvaccinated female, unvaccinated male with vaccinated female, both male and female vaccinated or both male and females unvaccinated). Among the different group of patients, no significant differences were found in IVF outcomes and semen quality [30]. In another retrospective cohort study, by Dong et al. [31], 409 males without previous SARS-CoV-2 infection showed a significant decrease in total sperm motility after vaccine administration (46.90 ± 2.40% vs. 58.62 ± 2.51%; p = 0.001). However, the parameter remained within the normal range, and all the other main semen parameters (volume, sperm concentration, total sperm count, progressive motility and normal forms) were not affected by significant modifications [31].

In conclusion, the evidence available does not support a negative effect of COVID-19 vaccines on semen quality and fertility rates of couples undergoing IVF. Notably, a significant limitation of the described studies is the definition of vaccine status mainly based on self-reports and the short follow-up period. Data from large longitudinal studies with adequate follow-up time could, therefore, add information in the future. However, a negative impact on fertility and semen parameters in subsequent months following the vaccination seems unlikely, considering that the scarcely significant alterations found in only a few cases were frequently resolved within the first few months following vaccination.

4. COVID-19 vaccination and advanced seminal parameters

Classic seminal parameters can provide important information in the assessment of an infertile subject, but there are clinical situations where data provided by these parameters may not be sufficient. In particular, in cases of unexplained infertility, where infertility is associated with basal seminal parameters in the normal range, or idiopathic infertility, where impaired classic seminal parameters were found without a defined clinical reason, advanced seminal parameters may be a valuable addition [43]. Indeed, these parameters provide useful information about sperm DNA integrity, chromatin status, anti-sperm antibodies, levels of reactive oxygen species (ROS), and the presence of inflammatory or pro-inflammatory factors. For example, they may be able to identify clinical situations where oxidative stress represents the predominant pathophysiological mechanism, leading to specific antioxidant treatments [44]. In fact, oxidative stress can impair fertility through alteration in classic semen parameters, but also damaging sperm membranes and DNA, leading to difficulties in the interaction between spermatozoa and egg even in the presence of normal classic semen parameters [45].

Current data on the effects of SARS-CoV-2 vaccines on advanced seminal parameters are limited (Table 2, Ref. [28, 46, 47, 48, 49, 50]). As an inflammatory disease, COVID-19 infection could increase oxidative stress, impairing both classical and advanced seminal parameters [2]. A commonly accepted hypothesis also suggests that vaccines may trigger an immune response that could temporarily disrupt spermatogenesis, potentially causing short-term declines in sperm quality, particularly when accompanied by a fever [35, 46]. This evidence was supported by a longitudinal cohort study conducted on 17 normozoospermic men who experienced changes in seminal parameters during both the acute post-vaccination phase (24–72 hours) and three months after the vaccination. While no significant changes in DNA integrity were observed, transient increases in monocyte chemoattractant protein-1 (MCP-1) and interleukin-8 (IL-8) levels in seminal plasma were detected, suggesting a brief activation of the immune system that could also affect the testes [47]. Likewise, a transient decline in sperm quality, particularly following COVID-19 infection, was suggested by Zhao et al. [48], who retrospectively investigated the effects of different COVID-19 vaccines (inactivated vaccines or recombinant protein vaccines) in a large cohort of men in China. They included 1639 vaccinated men who were subdivided, based on previous COVID-19 infection, into uninfected and previously infected (the latter subdivided by time of recovery from COVID-19 into less than 30 days, 30–90 days, and more than 90 days). 85.2% of the participants had suffered from COVID-19. Temporary but reversible increase in sperm DNA fragmentation index (DFI) and high DNA stainability (HDS), along with a rise in antisperm antibodies, was observed, particularly during the acute phase of infection (within 30 days), but all the observed changes disappeared over time from recovery. Notably, receiving two doses of an inactivated vaccine appeared to offer less protection to sperm quality compared to recombinant protein vaccine boosters [48]. An interesting study by Lestari et al. [49] examined the sperm DFI in 70 infertile men, comparing those who had been infected with COVID-19, those who had not, and those vaccinated with mRNA, inactivated viral, or viral vector vaccines. The men receiving the vaccination had not been previously affected by SARS-CoV-2. Interestingly, the men vaccinated with the viral vector vaccine exhibited a significant increase in DFI compared with those who received other vaccine types or men who were neither infected with SARS-CoV-2 nor vaccinated. However, the authors could not confirm the outcomes due to the lack of a further follow-up [49].

However, not all the studies suggested an adverse effect of COVID-19 vaccination on semen quality. In a case report by Chatzimeletiou et al. [50], the administration of three doses of an mRNA COVID-19 vaccine, combined with treatments for Ankylosing Spondylitis, was associated with an increase in sperm concentration, while motility, morphology, and DFI remained stable, suggesting no negative impact on sperm quality [50]. Similarly, Olana et al. [28] focused on the effects of the BNT162b2 mRNA COVID-19 vaccine on sperm parameters of 47 men, before and three months following vaccination, and no significant differences were detected in seminal electrolyte levels, interleukin-6 (IL-6) concentrations, or reactive oxygen metabolites [28]. Moreover, regarding DNA integrity and sperm chromatin condensation, no significant effects were observed when comparing the actions of different vaccine types [41].

In conclusion, while studies indicate that SARS-CoV-2 vaccination might cause temporary changes in some seminal parameters, such as DFI and chromatin condensation, these effects don’t seem to be significant or long-lasting. Differences found in sperm quality alterations among different types of vaccinations are interesting but difficult to explain. In fact, confounding factors, such as post vaccination fever, that could influence these parameters are not easy to evaluate. Overall, sperm quality tends to return to normal over time. However, more research is needed to confirm these results and to explore any potential long-term impacts.

5. COVID-19 vaccination and erectile function

In recent years, a correlation between COVID-19 and erectile dysfunction (ED) has been highlighted. Specifically, it has been observed that in the clinical context of “Long COVID”, multiple pathophysiological mechanisms can alter erectile function. This condition can in fact be associated with endothelial dysfunction, altered pulmonary function up to pulmonary fibrosis and alterations in the psychiatric sphere, such as anxiety and depression. These factors collectively contribute to vascular and psychological impairments that can affect erectile function [8, 9]. Considering this evidence, concerns have arisen about the possible negative effects of COVID-19 vaccination on sexual function. However, to date few studies have assessed the impact of COVID-19 vaccination on erectile function (Table 3, Ref. [51, 52, 53]).

Mehta et al. [51] evaluated the impact of vaccination on 465 sexually active Indian males aged between 20 and 50 years. The International Index of Erectile Function 15 (IIEF15) questionnaire was administered with an addition of 15 questions to evaluate general sexual function and the specific impact of COVID-19 vaccination on each sexual domain (erectile function, orgasmic function, sexual desire, intercourse satisfaction, and overall satisfaction). 71% of the patients reported no impact, 3% a decline, 2.7% an improvement, and 23.3% could not assess the impact of vaccination on sexual function. No differences, in terms of age, were found among the groups. Information regarding the type of vaccination administered was not reported; however, it is worthy to note that in the early phase of COVID-19 vaccination in India, 90% of the people vaccinated received Covishield ChAdOx1-S and 10% Covaxin BBV152. According to their results, the authors concluded that COVID-19 vaccination did not seem related to a significant adverse impact on male sexual function [51].

Similarly, Diaz et al. [52] conducted a survey on US males to evaluate the impact of COVID-19 vaccination on erectile function. 138 adult males were included, 121 vaccinated and 17 unvaccinated, according to the following criteria: age ≥45 years old and with no history of ED diagnosis. An anonymous 16-question survey, including the International Index of Erectile Function 5 (IIEF-5), was administered. The median IIEF-5 score among those vaccinated was 20, compared to 22 in the unvaccinated group. This finding was not statistically significant and cohort size differences had an important role, since 87.7% of patients were vaccinated. In conclusion, this survey showed no association between COVID-19 vaccination and new diagnosis of ED in males older than 45 years [52].

Başer et al. [53] conducted another online survey among healthcare professionals in Turkey. The survey included sexually active healthcare professionals having at least weekly intercourse, aged ≥18 years, who had received a complete immunization schedule. Exclusion criteria were a history of pelvic surgery or radiotherapy and psychiatric disorders. All the participants had to complete a questionnaire including the IIEF15, the Arizona Sexual Experiences Scale (ASEX) and the Beck anxiety inventory (BAI). A total of 170 participants were included. This study found an improvement, comparing pre- and post-vaccination, in IIEF, ASEX, and BAI scores and a statistically significant increase in the duration of sexual intercourse, showing positive changes in sexual functions after vaccination [53]. In conclusion, the evidence available does not suggest a negative effect of COVID-19 vaccination on sexual function. On the contrary, vaccination seems to play a protective role by mitigating the vascular and psychological consequences of COVID-19 infection.

In fact, in the study by Başer et al. [53] the administration of COVID-19 vaccines seems to ameliorate the quality of intercourse. These results are not surprising, since the link between COVID-19 and ED is well-established, and the COVID-19 vaccine administration could prevent or mitigate some of the detrimental effects of SARS-CoV-2 infection. However, it must be considered that the little evidence available derives from studies with significant limitations. Indeed, the study by Başer et al. [53] presented a probable selection bias by analysing only healthcare professionals, potentially leading to better results by removing the psychological component of fear related to the lack of knowledge of the vaccine. Instead, in the study by Diaz et al. [52] the presence of a relevantly larger number of vaccinated patients in comparison to unvaccinated ones created important cohort size effects leading to difficulties in the statistical evaluation of results.

6. COVID-19 vaccination and sex hormones

An association between SARS-CoV-2 infection and low serum testosterone levels has been reported [54]. Indeed, as a systemic inflammatory disease, COVID-19 may cause suppression of gonadotropic secretion by the pituitary gland that leads to decreased testosterone production by the testes (i.e., functional hypogonadism) [55]. In addition, COVID-19 may impair gonadotropin secretion through direct damage to the pituitary gland by causing hypophysitis or pituitary apoplexy [56, 57]. On the other hand, a possible direct effect of COVID-19 on testosterone testicular secretion has been suggested as well. That hypothesis is strengthened by the finding of a decline in testosterone levels in association with a rise in luteinizing hormone (LH), prolactin, and estradiol levels in a systematic review and meta-analysis of 2024 [7]. Despite the evidence concerning the effects of COVID-19 on gonadal function, few studies are available on the influence of COVID-19 vaccines on male hormones (Table 4, Ref. [42, 58, 59, 60]).

In 2024, a retrospective study evaluated 383 men with different vaccination status (unvaccinated, one dose, two doses or three doses of vaccine). Significantly higher levels of prolactin and follicular stimulating hormones (FSH) were found in men who received only one vaccine in comparison with the others, but the authors highlighted that the small sample size (only 11 patients were included in this group) could have conditioned their observation. Nonetheless, the total testosterone and LH levels showed no significant differences among the four groups [42].

Alteration in gonadotropin production has been described in association with specific pituitary disorders. Aliberti et al. [58] described a case of pituitary macroadenoma apoplexy, with the patient suffering from adrenal insufficiency and asymptomatic hypogonadotropic hypogonadism the day after his third dose of SARS-CoV-2 vaccine. The patient underwent tumor transsphenoidal resection and the pathology report showed pituitary adenoma with focal hemorrhage and necrosis. Interestingly, immunohistochemical evidence of SARS-CoV-2 proteins next to the pituitary capillaries suggested a previous exposure to SARS-CoV-2 as a contributing factor. The alterations described were transient considering that at the 4-month follow-up, a complete recovery of glucocorticoid and gonadotropic axis was observed, but the authors warned about the risk of pituitary apoplexy after vaccine in individuals with previous SARS-CoV-2 infection [58].

Hypophysitis after COVID-19 vaccination, with different clinical and biochemical manifestations, was also described. In a first case report, a 51-year-old man was suffering from headache, nausea, vomiting, malaise, and arthralgias a few days after the second dose of mRNA-1273 vaccination. Biochemical evaluations showed deficits of adrenal, thyrotropic, and gonadotropic axis, the latter associated with symptoms of hypogonadism, such as ED and decreased libido. The brain magnetic resonance imaging (MRI) was suggestive of hypophysitis, and during the follow-up, a spontaneous normalization of gonadotropic function was observed [59]. In another case report, a 59-year-old man with a history of Rathke’s cleft cyst was suffering from hypophysitis associated with a deficit of all pituitary tropins, but with normal testosterone levels after the second dose of non-specified COVID-19 vaccination. After one year of follow-up, symptoms of hypogonadism were reported, and hypogonadotropic hypogonadism was diagnosed [60]. Interestingly, the manifestations described occurred during the second or third vaccine doses, but not after the first one. We do not have enough data to evaluate if specific types of vaccines are associated with a major risk. The hypogonadotropic hypogonadism seems to be reversible in most cases [58, 59], but in one patient, it was diagnosed one year after the vaccination and remained permanent [60]. Also, clinical manifestations of hypogonadism seem to be variable and not described in all cases of hypogonadotropic hypogonadism [58, 59, 60]. Interestingly, pre-existing expansive pituitary lesions (macroadenoma or Rathke’s pouch cyst) were described in most cases [58, 60]; no relevant systemic diseases, no known coagulation disorders or autoimmune diseases were mentioned [58, 60]. Two main pathogenetic mechanisms were suggested: vaccine-induced thrombophilia-thrombocytopenia (VITT) syndrome or autoimmune/autoinflammatory syndrome induced by adjuvants (ASIA) [58]. It has been assumed that these two mechanisms occur more easily when the pituitary gland is abnormal and therefore “fragile”, as in the cases of expansive lesions [61]. It is worthy to note that Aliberti L. et al. [58] described the detection of the virus in the tissue of the resected macroadenoma and hypothesized that the patient previously had an asymptomatic COVID-19 infection, and that the vaccination triggered a cross-reaction resulting in bleeding at the pituitary level [58].

7. Conclusions

The evidence available clearly points to the absence of a clinically relevant effect of COVID-19 vaccination on semen parameters and male fertility, confirming the excessive concern raised in public opinion and fostered in part by misinformation on the topic. Regarding erectile function, even if only a few studies with important methodological limitations are available, a negative effect of vaccination seems to be unlikely. In addition, the negative effects of COVID-19 on erectile function derive from the virus’ biological activity which is not present in the vaccine, and therefore these negative effects should also be prevented. The more relevant findings regard some cases of pituitary apoplexy and hypophysitis with involvement of the gonadal axis. However, it should be noted that these events were particularly rare and occurred mainly in patients with known pituitary lesions. Finally, there is a lack of randomized controlled trials specifically focused on the effects of COVID-19 vaccines and male fertility.

Availability of data and materials

No new data were created or analyzed in this study. Data sharing is not applicable to this article.

Author contributions

AC, GS, and NdM—designed the research study and performed the research. AC, GS, NdM, NA, MP, SR, SS—wrote the manuscript. GB—supervised the work and provided important methodological insights. All authors contributed to editorial changes in the manuscript. All authors read and approved the final manuscript.

Ethics approval and consent to participate

Not applicable.

Acknowledgment

Not applicable.

Funding

This research received no external funding.

Conflict of interest

The authors declare no conflict of interest.