Stesura Seveso Archivio Italiano di Urologia e Andrologia 2024; 96(2):12449 1 ORIGINAL PAPER numerous unrelated pathogens, including several respira- tory infections such as influenza A and RSV (4). Interestingly, countries with higher rates of BCG immu- nization were observed to experience lower mortality rates from COVID-19 infections compared to countries with lower rates of immunization during the height of the pan- demic (5). BCG therapy also represents an important role in the field of urology. Intravesical BCG therapy is the gold- standard adjuvant therapy for non-muscle invasive bladder cancer (NMIBC) (6). Though its specific mechanism remains elusive, its therapeutic role in NMIBC has been attributed to local and systemic immune responses (7). Consequently, there was growing interest in a possible role for this therapy in protection against COVID-19 infection and symptom burden. Some evidence has suggested NMIBC patients receiving intravesical BCG therapy had lower COVID-19 case-fatality rate than the overall popula- tion (8). Further research on the role of BCG immunization and intravesical therapy on COVID-19 infection has been limited. As such, we sought to determine whether intrav- esical BCG and/or infantile BCG vaccination in patients with NMIBC affected the incidence of COVID-19 infection. METHODS Retrospective data collection of patients with high-risk NMIBC diagnosed after January 1, 2015, from two Canadian centers. Data collection included basic demo- graphic (age/sex/race), clinical (smoking history/comor- bidities/prior BCG vaccination or tuberculosis infection), pathologic (stage/grade of tumour), treatment (intravesi- cal BCG/chemo) and outcome (recurrence/progression) variables. Details on BCG including the number of instil- lations and duration of treatment were obtained. A simple survey was also sent to patients to record possi- ble signs and symptoms of COVID-19, or a documented infection. The severity of COVID-19 infection was meas- ured by hospitalization, admission to ICU and death. The survey was sent at the end of the pandemic. RESULTS In this study, 348 patients who had been diagnosed with high-risk NMIBC were included. All patients lived in Canada, however, 188 were from Ontario and 160 were Introduction: The study aimed to correlate the history of intravesical BCG as well as infantile BCG immunization with the incidence and severity of COVID-19 infection. Methods: Retrospective data collection of patients with high-risk non muscle invasive bladder cancer (NMIBC) from two Canadian centers. Data collection included a history of BCG instillation, infantile immunization, and the development of COVID-19 infection. Admission and/ or mortality because of COVID-19 was reported. Results: We could include data from 348 patients: including 188 and 160 patients from Ontario and British Columbia respective- ly. COVID-19 affected 15% of these patients. Intravesical BCG was used in 44% of these patients. Intravesical BCG and/or infantile BCG immunization did not correlate with the incidence of COVID-19 infection. Conclusions: Previous intravesical BCG and/ or a history of infantile BCG vaccination were not more/ less frequent in patients who had COVID-19 infection. KEY WORDS: Bladder cancer; BCG; COVID-19. Submitted 4 March 2024; Accepted 28 March 2024 INTRODUCTION The COVID-19 pandemic represented an unprecedented time in modern society, resulting in mortality and morbid- ity worldwide, as well as significant strain on healthcare resources and professionals. Early in the pandemic, tremendous efforts were put forth to identify a vaccination against the etiologic agent in COVID-19 infection, SARS- CoV-2 virus. This infection is associated with deregulation of innate immune responses, ultimately resulting in sys- temic inflammation and mass virus replication (1). Trained immunity (TI) is a non-specific, protective inflammatory response generated from immunization against an unrelat- ed pathogen (2). As such, TI was proposed as a mechanism to tackle infection and spread by creating an early immune response (1). Prior to the creation of COVID-19 specific immunizations, there was interest in the Bacillus Calmette- Guérin (BCG) vaccine for protection against COVID-19. The BCG immunization contains live-attenuated Mycobacterium bovis and is used to protect against tuber- culosis in countries with high incidence (3). The BCG vac- cine has reliably demonstrated TI, protecting against Does intravesical Bacillus Calmette-Guérin for bladder cancer protect from COVID-19? Anastasia MacDonald 1, Lexia Bao 2, Vahid Mehrnoush 1, Asmaa Ismail 1, Livio Di Matteo 3, Ahmed Zakaria 1, Hazem Elmansy 1, Peter Black 2, Ahmed Kotb 1 1 Department of Urology, Northern Ontario School of Medicine University, Thunder Bay, ON, Canada; 2 Department of Urology, University of British Columbia, BC, Canada; 3 Department of Economics, Lakehead University, Thunder Bay, ON, Canada. DOI: 10.4081/aiua.2024.12449 Summary Archivio Italiano di Urologia e Andrologia 2024; 96(2):12449 A. MacDonald, L. Bao, V. Mehrnoush, A. Ismail, et al. 2 from British Columbia. The mean age was 74 ± 10. Of the 348 participants, 44% (n = 152) had received intravesical BCG therapy. History of BCG immunization could only be obtained from the Ontario cohort, with 60% (n = 113) being immunized. It was observed that 24% (n = 45) of the Ontario cohort had received both intravesical BCG therapy and had a history of infantile BCG immunization. Overall, 15% of participants were infected with COVID- 19. There was no significant difference in the incidence of COVID-19 infection between those with and without a history of infantile BCG immunization (p > 0.05) and between those who had and had not received intravesical BCG therapy (p > 0.05). Comparison of those with BCG immunization and/or BCG intravesical therapy and those with neither intervention did not identify a significant dif- ference in COVID-19 (p > 0.05). Additionally, there was no significant difference in COVID-19 incidence between those with a combined history of intravesical BCG and BCG immunization with other participants (p > 0.05). Table 1 illustrates these findings. The median number of BCG doses administered was the same in patients who had been infected with COVID-19 and those who had not (12 vs. 12 doses; p > 0.05). There was one incidence of mortality attributed to COVID-19 infection in a patient who did not receive intravesical BCG nor had infantile BCG. Three cases required non-ICU hospital admission. This included 2 patients who received both infantile and intravesical BCG and one patient who did not receive either. The 3 cases recovered well. DISCUSSION Given the widespread implications of COVID-19 infec- tion, significant efforts have been made to understand the relationships between this infection and well-established medical practices. BCG immunization has reliably demonstrated the ability to confer non-specific protection against various illnesses (4). The ability of intravesical BCG therapy to induce such protection remains unclear, although laboratory investigations have suggested intrav- esical BCG is capable of TI (9). High-risk NMIBC patients who had received intravesical BCG therapy represent a unique group of patients during the pandemic, as they had been treated with an agent hypothesized to confer protection against the SARS-CoV-2 virus. Our study did not identify a relationship between intraves- ical BCG administration and COVID-19 infection. This is perhaps unsurprising as BCG therapy is administered locally to the bladder to prevent the recurrence of bladder cancer. Studies have suggested the ability of intravesical BCG to confer TI against some respiratory infections, how- ever, these have not been assessed in human studies9. While these installations are believed to generate both local and systemic inflammatory responses (5), the systemic response may not be strong or broad enough to directly prevent COVID-19. This may be supported by a study by Gallegos et al. (2021), that identified a higher cumulative incidence of COVID-19 infection, but lower overall mor- tality in patients who completed intravesical BCG therapy for NMIBC compared to the general population. These authors theorized that intravesical BCG immunization may confer protective benefits in terms of COVID-19 severity, rather than the development of infection (8). Interestingly, Pichler et al. (2023) assessed the ability of intravesical BCG to induce adaptive and innate immuni- ty. They found that repetitive BCG instillations were able to elicit an innate immune response and thus TI in a lab- oratory setting. It was theorized that it would require a minimum of 6 weeks to elicit this response (10). In our study, those who developed COVID-19 infection and those who did not both received a median number of 12 doses of intravesical BCG, thus spanning a course longer than 6 weeks. Despite this, there was no difference in the incidence of COVID-19 infection in those receiving BCG immunotherapy. Our data also demonstrated no correlation between BCG immunization and COVID-19 infection. Given the many examples of TI protection from BCG immunization, there was strong speculation about its ability to protect against SARS-CoV-2 as well. This was supported by the observa- tion that countries with mandatory BCG immunization experienced a lower number of COVID-19 cases, in addi- tion to reduced mortality (11). Despite this observation, the World Health Organization (WHO) declared that there was no evidence that the BCG vaccine can protect against COVID-19 (12). Before the development of COVID-19- specific immunizations, several randomized control trials had been started to determine the efficacy of BCG immu- nization to protect against this infection (13). There were several limitations to our study. While intrav- esical BCG therapy was assessed at two centers, the histo- ry of immunization was only assessed at a single center and thus faced inevitable selection bias. Further, our study did not account for the comorbidities of patients, which may have influenced their susceptibility to COVID-19 infection. In this study, we only assessed inci- dence of COVID-19 infection. Future work may seek to categorize the severity and mortality of these patients. CONCLUSIONS Overall, this study did not identify a relationship between the incidence of COVID-19 infection and a history of intravesical BCG therapy or BCG immunization in NMIBC patients. The number of intravesical BCG doses received by those who were and were not infected did not vary. Based on these results, it can be concluded that nei- ther form of BCG therapy confers protection against this infection. Table 1. Correlation between BCG vaccination and the development of COVID-19 infection. No COVID-19 COVID-19 P value Infantile BCG No 58 17 0.3 Yes 79 34 Intravesical BCG No 161 35 0.1 Yes 135 17 Infantile and/ or intravesical BCG No 31 13 0.7 Yes 106 38 Infantile and intravesical BCG No 105 38 0.8 Archivio Italiano di Urologia e Andrologia 2024; 96(2):12449 3 BCG COVID-19 REFERENCES 1. Kaur G, Singh S, Nanda S, et al. Fiction and Facts about BCG Imparting Trained Immunity against COVID-19. Vaccines 2022; 10:1006. 2. Gong W, Aspatwar A, Wang S, et al. COVID-19 pandemic: SARS- CoV-2 specific vaccines and challenges, protection via BCG trained immunity, and clinical trials. Expert Rev Vaccines 2021; 20:857-880. 3. Okafor CN, Rewane A, Momodu II. Bacillus Calmette Guerin. 2023 Jul 3. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2024. 4. Koneru G, Batiha GE, Algammal AM, et al. BCG Vaccine-Induced Trained Immunity and COVID-19: Protective or Bystander? Infect Drug Resist. 2021; 14:1169-1184. 5. Miyasaka M. Is BCG vaccination causally related to reduced COVID-19 mortality? EMBO Mol Med. 2020; 12:e12661. 6. Saginala K, Barsouk A, Aluru JS, et al. Epidemiology of Bladder Cancer. Med Sci (Basel). 2020; 8:15. 7. Livak KJ, Schmittgen TD. Analysis of relative gene expression data using real-time quantitative PCR and the 2(-Delta Delta C(T)) Method. Methods (San Diego, Calif.), 2001; 25:402-408. 8. Gallegos H, Rojas PA, Sepúlveda F, et al. 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COVID- 19 impact on bladder cancer-orientations for diagnosing, decision making, and treatment. Am J Clin Exp Urol. 2021; 9:132-139. Correspondence Anastasia MacDonald anamacdonald@nosm.ca Vahid Mehrnoush vahidmehrnoush7@gmail.com Asmaa Ismail asmaaismail0782@gmail.com Ahmed Zakaria aszakaria81@yahoo.com Hazem Elmansy hazem.mansy@rocketmail.com Ahmed Kotb; MD, PhD, FRCSC, FRCS Urol, FEBU Associate Professor drahmedfali@gmail.com Department of Urology, NOSM U, Thunder Bay, ON, Canada Lexia Bao lexia.bao@ubc.ca Peter Black peter.black@ubc.ca Department of Urology, University of British Columbia, BC, Canada Livio Di Matteo ldimatte@lakeheadu.ca Department of Economics, Lakehead University, Thunder Bay, ON, Canada Conflict of interest: The authors declare no potential conflict of interest.