Correlation between COVID-19 case fatality rate and percentage of BCG vaccination: is it true the vaccine is protective?

Spurious early ecological association suggesting BCG vaccination effectiveness for COVID-19

BACKGROUND

Several ecologic studies have suggested that the bacillus Calmette-Guérin (BCG) vaccine may be protective against SARS-CoV-2 infection including a highly-cited published pre-print by Miller et al., finding that middle/high- and high-income countries that never had a universal BCG policy experienced higher COVID-19 burden compared to countries that currently have universal BCG vaccination policies. We provide a case study of the limitations of ecologic analyses by evaluating whether these early ecologic findings persisted as the pandemic progressed.

METHODS

Similar to Miller et al., we employed Wilcoxon Rank Sum Tests to compare population medians in COVID-19 mortality, incidence, and mortality-to-incidence ratio between countries with universal BCG policies compared to those that never had such policies. We then computed Pearson's r correlations to evaluate the association between year of BCG vaccination policy implementation and COVID-19 outcomes. We repeated these analyses for every month in 2020 subsequent to Miller et al.'s March 2020 analysis.

RESULTS

We found that the differences in COVID-19 burden associated with BCG vaccination policies in March 2020 generally diminished in magnitude and usually lost statistical significance as the pandemic progressed. While six of nine analyses were statistically significant in March, only two were significant by the end of 2020.

DISCUSSION

These results underscore the need for caution in interpreting ecologic studies, given their inherent methodological limitations, which can be magnified in the context of a rapidly evolving pandemic in which there is measurement error of both exposure and outcome status.

Fiction and Facts about BCG Imparting Trained Immunity against COVID-19

The Bacille Calmette-Guérin or BCG vaccine, the only vaccine available against Mycobacterium tuberculosis can induce a marked Th1 polarization of T-cells, characterized by the antigen-specific secretion of IFN-γ and enhanced antiviral response. A number of studies have supported the concept of protection by non-specific boosting of immunity by BCG and other microbes. BCG is a well-known example of a trained immunity inducer since it imparts ‘non-specific heterologous’ immunity against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the virus responsible for the recent pandemic. SARS-CoV-2 continues to inflict an unabated surge in morbidity and mortality around the world. There is an urgent need to devise and develop alternate strategies to bolster host immunity against the coronavirus disease of 2019 (COVID-19) and its continuously emerging variants. Several vaccines have been developed recently against COVID-19, but the data on their protective efficacy remains doubtful. Therefore, urgent strategies are required to enhance system immunity to adequately defend against newly emerging infections. The concept of trained immunity may play a cardinal role in protection against COVID-19. The ability of trained immunity-based vaccines is to promote heterologous immune responses beyond their specific antigens, which may notably help in defending against an emergency situation such as COVID-19 when the protective ability of vaccines is suspicious. A growing body of evidence points towards the beneficial non-specific boosting of immune responses by BCG or other microbes, which may protect against COVID-19. Clinical trials are underway to consider the efficacy of BCG vaccination against SARS-CoV-2 on healthcare workers and the elderly population. In this review, we will discuss the role of BCG in eliciting trained immunity and the possible limitations and challenges in controlling COVID-19 and future pandemics.

Why Does the Severity of COVID-19 Differ With Age?: Understanding the Mechanisms Underlying the Age Gradient in Outcome Following SARS-CoV-2 Infection

Although there are many hypotheses for the age-related difference in the severity of COVID-19, differences in innate, adaptive and heterologous immunity, together with differences in endothelial and clotting function, are the most likely mechanisms underlying the marked age gradient. Children have a faster and stronger innate immune response to SARS-CoV-2, especially in the nasal mucosa, which rapidly controls the virus. In contrast, adults can have an overactive, dysregulated and less effective innate response that leads to uncontrolled pro-inflammatory cytokine production and tissue injury. More recent exposure to other viruses and routine vaccines in children might be associated with protective cross-reactive antibodies and T cells against SARS-CoV-2. There is less evidence to support other mechanisms that have been proposed to explain the age-related difference in outcome following SARS-CoV-2 infection, including pre-existing immunity from exposure to common circulating coronaviruses, differences in the distribution and expression of the entry receptors ACE2 and TMPRSS2, and difference in viral load.

Current Status and a Future Perspective of COVID-19 in Egypt: Egyptian Reference Laboratory Experience

Currently, the sole global concern is recurring waves of the COVID-19 virus that began in 2020 and is ongoing. This study aimed to compare the trends of COVID-19 infections in Egypt during the different waves. We calculated the COVID-19 positivity rate between March 2020 and the fourth week of April 2021 among those tested at the Reference Laboratory of the Egyptian University Hospitals. We then compared our results with those obtained from the WHO and the Egyptian Ministry of Health and Population websites. A dramatic increase in the positivity rate was observed during May and June 2020 (26.35% and 33.11%, respectively). This was followed by an abrupt reduction in July (11.7%), and flattening until a second increase was noted during November (9.6%), which reached its peak during December (17.8%). However, after the figures declined during January 2021, they began to rise again in February 2021 and continued to increase until the end of April 2021, simulating the first wave data. The analysis of the COVID-19 growth rate from April 1st to the 25th, 2021 revealed a slight downward trend in new cases. Data from both the WHO and the Egyptian Ministry of Health and Population websites showed similar patterns to our results. The third wave of COVID-19 started in Egypt. Analyzing future data can aid in forecasting the COVID-19 epidemic and allow us to use foresight to enact effective measures and strategies to keep this virus under control.

The Impact of COVID-19 Disease on Urology Practice

The diagnosis and timely treatment of cancer patients should not be compromised during an infectious disease pandemic. The pandemic of coronavirus disease 2019 (COVID-19) has serious implications on urology practice and raises particular questions for urologists about the management of different conditions. It was recommended to cancel most of the elective urological surgeries. Urological cancers surgeries that should be prioritized are radical cystectomy for selective tumors, orchiectomy for suspected testicular tumors, nephrectomy for c T3 + , nephroureterectomy for high-grade disease, and radical adrenalectomy for tumors >6 cm or adrenal carcinoma. Most prostatectomies can be delayed without compromising the survival rate of patients. Urological emergencies should be treated adequately even during this pandemic. There is a potential risk of coronavirus diffusion during minimally invasive procedures performed. It is crucial to use specific precautions when urologists performed those type of surgeries. It was also recommended to suspend the kidney transplantation program during the COVID-19 pandemic except for specific cases. In this review, we discussed the triage of urological surgeries, the risk of minimally invasive urological procedure, the kidney transplantation challenges, the systemic therapies, intravesical instillation of Bacillus Calmette-Guérin (BCG), endourology, teleconferencing, and telemedicine application in urology during the COVID-19 pandemic.

The possible puzzles of BCG vaccine in protection against COVID-19 infection

Background

The paper aimed to analyze and evaluate the present literature data on the clinical effectiveness of using the bacillus Calmette–Guérin (BCG) vaccine in protecting against the novel coronavirus disease 2019 (COVID-19).

Main body

Several novel clinical data have shown a relationship between the vaccinated population with the bacillus Calmette–Guérin (BCG) vaccine and the severity and mortality rate from coronavirus disease 2019 (COVID-19). However, the linkage between the BCG vaccine and COVID-19 infection mortality and morbidity rate is still ambiguous. The BCG has been protected previously from many other respiratory viral infections. The efficacy of the BCG vaccine in the protection against COVID-19 depends on various factors including social, economic, cultural norms, mitigation efforts, health infrastructure, and demographic differences between countries.

Conclusion

Thus, the literature analyses show a noticed difference between the countries that follow national vaccination programs than in countries that do not follow such programs (Italy, Netherlands, USA). However, there are not any recommendations for using BCG in the protection against severe cases of COVID-19. The severity of COVID-19 maybe depends on the age, immune state of the patient, and the level of vaccine coverage. The possible reason for BCG protection is trained immunity in both diseases.

SARS-CoV-2: Immune Response Elicited by Infection and Development of Vaccines and Treatments

The World Health Organization (WHO) announced in March a pandemic caused by Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2). This new infectious disease was named Coronavirus Disease 19 (COVID-19), and at October 2020, more than 39,000,000 cases of SARS-CoV-2 have been detected worldwide leading to near 1,100,000 deaths. Clinically, COVID-19 is characterized by clinical manifestations, such as fever, dry cough, headache, and in more severe cases, respiratory distress. Moreover, neurological-, cardiac-, and renal-related symptoms have also been described. Clinical evidence suggests that migration of immune cells to the affected organs can produce an exacerbated release of proinflammatory mediators that contribute to disease and render the immune response as a major player during the development of the COVID-19 disease. Due to the current sanitary situation, the development of vaccines is imperative. Up to the date, 42 prototypes are being tested in humans in different clinical stages, with 10 vaccine candidates undergoing evaluation in phase III clinical trials. In the same way, the search for an effective treatment to approach the most severe cases is also in constant advancement. Several potential therapies have been tested since COVID-19 was described, including antivirals, antiparasitic and immune modulators. Recently, clinical trials with hydroxychloroquine-a promising drug in the beginning-were suspended. In addition, the Food and Drug Administration (FDA) approved convalescent serum administration as a treatment for SARS-CoV-2 patients. Moreover, monoclonal antibody therapy is also under development to neutralize the virus and prevent infection. In this article, we describe the clinical manifestations and the immunological information available about COVID-19 disease. Furthermore, we discuss current therapies under study and the development of vaccines to prevent this disease.