Is BCG vaccination affecting the spread and severity of COVID-19?

Sex disparities of the effect of the COVID-19 pandemic on mortality among patients living with tuberculosis in the United States

Background

We aimed to determine the trend of TB-related deaths during the COVID-19 pandemic.

Methods

TB-related mortality data of decedents aged ≥25 years from 2006 to 2021 were analyzed. Excess deaths were estimated by determining the difference between observed and projected mortality rates during the pandemic.

Results

A total of 18,628 TB-related deaths were documented from 2006 to 2021. TB-related age-standardized mortality rates (ASMRs) were 0.51 in 2020 and 0.52 in 2021, corresponding to an excess mortality of 10.22 and 9.19%, respectively. Female patients with TB demonstrated a higher relative increase in mortality (26.33 vs. 2.17% in 2020; 21.48 vs. 3.23% in 2021) when compared to male. Female aged 45-64 years old showed a surge in mortality, with an annual percent change (APC) of -2.2% pre-pandemic to 22.8% (95% CI: -1.7 to 68.7%) during the pandemic, corresponding to excess mortalities of 62.165 and 99.16% in 2020 and 2021, respectively; these excess mortality rates were higher than those observed in the overall female population ages 45-64 years in 2020 (17.53%) and 2021 (33.79%).

Conclusion

The steady decline in TB-related mortality in the United States has been reversed by COVID-19. Female with TB were disproportionately affected by the pandemic.

Association between presence of Bacillus Calmette-Guerin vaccine scar and coronavirus disease 2019

Bacillus Calmette-Guerin vaccine is administered for protection against tuberculosis and may also have beneficial effects against some viral respiratory tract infections. In this study, it was aimed to investigate the relationship between Bacillus Calmette-Guerin vaccination which is confirmed by BCG scar, and the frequency and course of Coronavirus disease 2019 (COVID-19). Among 490 patients, 400 patients who accepted to participate in the study were included. After the consent of patients, age, gender, body mass index, comorbidities, smoking, history, and the progress of COVID-19 of these patients were investigated; the presence and number of Bacillus Calmette-Guerin scars were recorded by a physician. Data from groups with and without COVID-19 history were compared. There was no relation between presence and number of the BCG scar and COVID-19 related hospitalization and intensive care unit admission. When groups with and without COVID-19 history compared, no statistically significant difference was found with the presence and number of Bacillus Calmette-Guerin scars (P > 0,05). No association was found between the presence or number of BCG scars and the frequency and course of COVID-19 in individuals with Bacillus Calmette-Guerin vaccination history confirmed by the presence of Bacillus Calmette-Guerin vaccine scars. Currently, the most important protection against COVID-19 is the COVID-19 vaccine.

BCG and SARS-CoV-2-What Have We Learned?

Despite controversy over the protective effect of the BCG (Bacille Calmette-Guérin) vaccine in preventing pulmonary tuberculosis (TB) in adults, it has been used worldwide since 1921. Although the first reports in the 1930s had noted a remarkable decrease in child mortality after BCG immunization, this could not be explained solely by a decrease in mortality from TB. These observations gave rise to the suggestion of nonspecific beneficial effects of BCG vaccination, beyond the desired protection against M. tuberculosis. The existence of an innate immunity-training mechanism based on epigenetic changes was demonstrated several years ago. The emergence of the pandemic caused by the severe acute respiratory syndrome coronavirus (SARS-CoV-2) in 2019 revived the debate about whether the BCG vaccine can affect the immune response against the virus or other unrelated pathogens. Due to the mortality of the coronavirus disease (COVID-19), it is important to verify each factor that may have a potential protective value against the severe course of COVID-19, complications, and death. This paper reviews the results of numerous retrospective studies and prospective trials which shed light on the potential of a century-old vaccine to mitigate the pandemic impact of the new virus. It should be noted, however, that although there are numerous studies intending to verify the hypothesis that the BCG vaccine may have a beneficial effect on COVID-19, there is no definitive evidence on the efficacy of the BCG vaccine against SARS-CoV-2.

Multiple BCG vaccinations for the prevention of COVID-19 and other infectious diseases in type 1 diabetes

There is a need for safe and effective platform vaccines to protect against coronavirus disease 2019 (COVID-19) and other infectious diseases. In this randomized, double-blinded, placebo-controlled phase 2/3 trial, we evaluate the safety and efficacy of a multi-dose Bacillus Calmette-Guérin (BCG) vaccine for the prevention of COVID-19 and other infectious disease in a COVID-19-unvaccinated, at-risk-community-based cohort. The at-risk population is made of up of adults with type 1 diabetes. We enrolled 144 subjects and randomized 96 to BCG and 48 to placebo. There were no dropouts over the 15-month trial. A cumulative incidence of 12.5% of placebo-treated and 1% of BCG-treated participants meets criteria for confirmed COVID-19, yielding an efficacy of 92%. The BCG group also displayed fewer infectious disease symptoms and lesser severity and fewer infectious disease events per patient, including COVID-19. There were no BCG-related systemic adverse events. BCG's broad-based infection protection suggests that it may provide platform protection against new severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) variants and other pathogens.

A century of BCG vaccination: Immune mechanisms, animal models, non-traditional routes and implications for COVID-19

Bacillus Calmette-Guerin (BCG) has been used as a vaccine against tuberculosis since 1921 and remains the only currently approved vaccine for this infection. The recent discovery that BCG protects against initial infection, and not just against progression from latent to active disease, has significant implications for ongoing research into the immune mechanisms that are relevant to generate a solid host defense against Mycobacterium tuberculosis (Mtb). In this review, we first explore the different components of immunity that are augmented after BCG vaccination. Next, we summarize current efforts to improve the efficacy of BCG through the development of recombinant strains, heterologous prime-boost approaches and the deployment of non-traditional routes. These efforts have included the development of new recombinant BCG strains, and various strategies for expression of important antigens such as those deleted during the M. bovis attenuation process or antigens that are present only in Mtb. BCG is typically administered via the intradermal route, raising questions about whether this could account for its apparent failure to generate long-lasting immunological memory in the lungs and the inconsistent level of protection against pulmonary tuberculosis in adults. Recent years have seen a resurgence of interest in the mucosal and intravenous delivery routes as they have been shown to induce a better immune response both in the systemic and mucosal compartments. Finally, we discuss the potential benefits of the ability of BCG to confer trained immunity in a non-specific manner by broadly stimulating a host immunity resulting in a generalized survival benefit in neonates and the elderly, while potentially offering benefits for the control of new and emerging infectious diseases such as COVID-19. Given that BCG will likely continue to be widely used well into the future, it remains of critical importance to better understand the immune responses driven by it and how to leverage these for the design of improved vaccination strategies against tuberculosis.

An insight into SARS-CoV-2 structure, pathogenesis, target hunting for drug development and vaccine initiatives

SARS-CoV-2, the virus responsible for the COVID-19 pandemic, has been confirmed to be a new coronavirus having 79% and 50% similarity with SARS-CoV and MERS-CoV, respectively. For a better understanding of the features of the new virus SARS-CoV-2, we have discussed a possible correlation between some unique features of the genome of SARS-CoV-2 in relation to pathogenesis. We have also reviewed structural druggable viral and host targets for possible clinical application if any, as cases of reinfection and compromised protection have been noticed due to the emergence of new variants with increased infectivity even after vaccination. We have also discussed the types of vaccines that are being developed against SARS-CoV-2. In this review, we have tried to give a brief overview of the fundamental factors of COVID-19 research like basic virology, virus variants and the newly emerging techniques that can be applied to develop advanced treatment strategies for the management of COVID-19 disease.

Comorbidities and autopsy findings of COVID-19 deaths and their association with time to death: a systematic review and meta-analysis

OBJECTIVE

Examination of postmortem findings can help establish effective therapeutic strategies to reduce mortality. The aim of this study was therefore to review complete autopsy cases and their postmortem findings and comorbidities associated with death caused by COVID-19, in order to establish a profile of the deceased and the likelihood of time to death.

METHODS

A systematic review was carried out following the recommendations of the Preferred Reporting Items for Systematic Reviews and Meta-Analyses and meets Cochrane criteria recommendations (PROSPERO registration number CRD 42020209649). An electronic search in the databases Pubmed, Scopus, Web of Science, Wiley Online Library, and Scientific Electronic Library Online (SciELO) was performed.

RESULTS

The search strategy yielded a total of 25 articles where 140 cases of complete autopsies were reported. The most prevalent comorbidity was vascular diseases. Patients with vascular disease, heart disease, and diabetes died significantly in a shorter period of time. Autopsies mainly focused on the lungs. The proliferative phase of Diffuse Alveolar Damage (DAD) was the most reported in the microscopic postmortem findings, and these patients died in a shorter period of time. However, individuals aged over 80 years significantly presented fibrotic phase of DAD at the time of death. The kidney was the second most affected organ with thrombosis and tubular damage, followed by the liver with congestion and necrosis.

CONCLUSION

Given that accurate information of complete autopsies findings is still scarce, it is necessary to perform complete autopsies by examining organs other than the lungs in order to provide information to improve new treatment strategies in patients with a high risk of mortality.

A subunit vaccine candidate based on the Spike protein of SARS-CoV-2 prevents infectious virus shedding in cats

Of the numerous animal species affected by the SARS-CoV-2 virus, cats are one of the most susceptible, and cat-to-cat transmission has been described. Although cat-to-human infection has not, as yet, been demonstrated, preventive measures should be taken in order to avoid both viral infection in cats and transmission among them. In this respect, the application of an effective vaccine to at-risk populations would be a useful tool for controlling the disease in this species. Here, we test a new vaccine prototype based on the Spike protein of the virus in order to prevent infection and infectious virus shedding in cats. The vaccine employed in experimentation, and which is easily produced, triggered a strong neutralizing antibody response in vaccinated animals. In contrast to that which occurred with control animals, no infectious virus was detected in the oropharyngeal or rectal swabs of vaccinated cats submitted to a SARS-CoV-2 challenge. These results are of great interest as regards future considerations related to implementing vaccination programs in pets. The value of cats as vaccination trial models is also described herein.

Influence of Aerosol Delivered BCG Vaccination on Immunological and Disease Parameters Following SARS-CoV-2 Challenge in Rhesus Macaques

The tuberculosis vaccine, Bacille Calmette-Guerin (BCG), also affords protection against non-tuberculous diseases attributable to heterologous immune mechanisms such as trained innate immunity, activation of non-conventional T-cells, and cross-reactive adaptive immunity. Aerosol vaccine delivery can target immune responses toward the primary site of infection for a respiratory pathogen. Therefore, we hypothesised that aerosol delivery of BCG would enhance cross-protective action against severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) infection and be a deployable intervention against coronavirus disease 2019 (COVID-19). Immune parameters were monitored in vaccinated and unvaccinated rhesus macaques for 28 days following aerosol BCG vaccination. High-dose SARS-CoV-2 challenge was applied by intranasal and intrabronchial instillation and animals culled 6–8 days later for assessment of viral, disease, and immunological parameters. Mycobacteria-specific cell-mediated immune responses were detected following aerosol BCG vaccination, but SARS-CoV-2-specific cellular- and antibody-mediated immunity was only measured following challenge. Early secretion of cytokine and chemokine markers associated with the innate cellular and adaptive antiviral immune response was detected following SARS-CoV-2 challenge in vaccinated animals, at concentrations that exceeded titres measured in unvaccinated macaques. Classical CD14+ monocytes and Vδ2 γδ T-cells quantified by whole-blood immunophenotyping increased rapidly in vaccinated animals following SARS-CoV-2 challenge, indicating a priming of innate immune cells and non-conventional T-cell populations. However, viral RNA quantified in nasal and pharyngeal swabs, bronchoalveolar lavage (BAL), and tissue samples collected at necropsy was equivalent in vaccinated and unvaccinated animals, and in-life CT imaging and histopathology scoring applied to pulmonary tissue sections indicated that the disease induced by SARS-CoV-2 challenge was comparable between vaccinated and unvaccinated groups. Hence, aerosol BCG vaccination did not induce, or enhance the induction of, SARS-CoV-2 cross-reactive adaptive cellular or humoral immunity, although an influence of BCG vaccination on the subsequent immune response to SARS-CoV-2 challenge was apparent in immune signatures indicative of trained innate immune mechanisms and primed unconventional T-cell populations. Nevertheless, aerosol BCG vaccination did not enhance the initial clearance of virus, nor reduce the occurrence of early disease pathology after high dose SARS-CoV-2 challenge. However, the heterologous immune mechanisms primed by BCG vaccination could contribute to the moderation of COVID-19 disease severity in more susceptible species following natural infection.

BCG vaccination induces cross-protective immunity against pathogenic microorganisms

Bacillus Calmette-Guérin (BCG) is an attenuated Mycobacterium bovis strain used as a vaccine to prevent Mycobacterium tuberculosis (M. tb) infection. Its ability to potentiate the immune response induced by other vaccines and to promote nonspecific immunomodulatory effects has been described. These effects can be triggered by epigenetic reprogramming and metabolic shifts on innate immune cells, a phenomenon known as trained immunity. The induction of trained immunity may contribute to explain why BCG vaccination effectively decreases disease symptoms caused by pathogens different from M. tb. This article explains the importance of BCG immunization and the possible mechanisms associated with the induction of trained immunity, which might be used as a strategy for rapid activation of the immune system against unrelated pathogens.

BCG vaccination and the risk of COVID 19: A possible correlation

Bacillus Calmette-Guérin (BCG) vaccine is currently used to prevent tuberculosis infection. The vaccine was found to enhance resistance to certain types of infection including positive sense RNA viruses. The current COVID-19 pandemic is caused by positive sense RNA, severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). A higher mortality rate of COVID-19 patients was reported in countries where BCG vaccination is not routinely administered, when compared to the vaccinated ones. We hypothesized that BCG vaccine may control SARS-CoV2 infection via modulating the monocyte immune response. We analyzed GSE104149 dataset to investigate whether human monocytes of BCG-vaccinated individuals acquire resistance to SARS-CoV-2 infection. Differentially expressed genes obtained from the dataset were used to determine enriched pathways, biological processes, and molecular functions for monocytes post BCG vaccination. Our data show that BCG vaccine promotes a more effective immune response of monocytes against SARS-CoV2, but probably not sufficient to prevent the infection.

Recent Advancements on COVID-19: A Comprehensive Review

Over the last few decades, there have been several global outbreaks of severe respiratory infections. The causes of these outbreaks were coronaviruses that had infected birds, mammals and humans. The outbreaks predominantly caused respiratory tract and gastrointestinal tract symptoms and other mild to very severe clinical signs. The current coronavirus disease-2019 (COVID-19) outbreak, caused by the novel severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), is a rapidly spreading illness affecting millions of people worldwide. Among the countries most affected by the disease are the United States of America (USA), India, Brazil, and Russia, with France recording the highest infection, morbidity, and mortality rates. Since early January 2021, thousands of articles have been published on COVID-19. Most of these articles were consistent with the reports on the mode of transmission, spread, duration, and severity of the sickness. Thus, this review comprehensively discusses the most critical aspects of COVID-19, including etiology, epidemiology, pathogenesis, clinical signs, transmission, pathological changes, diagnosis, treatment, prevention and control, and vaccination.

Exploring the role of bacillus calmette-guerin vaccination in protection against COVID-19

Background

In recent studies, it has been established that countries having Bacillus Calmette-Guerin (BCG) vaccination programs reported less COVID-19 cases and deaths per population Preliminary studies suggest that BCG vaccination could upregulate the vaccine-induced immunity against SARS-CoV-2. Hence, the recent study was aimed to determine the association of BCG vaccine with the development of COVID-19 in health care workers.

Methods

The participants included in the study were healthcare workers (doctors, paramedics, and other supporting staff) working in the high and low-risk zones of COVID-19 in the hospital. The Graph Pad statistical analysis tool was used to determine the association of preliminary BCG vaccination with their COVID-19 status.

Results

A total of 200 health care workers working in different departments of the hospital were enrolled in the study. The relative risk of COVID-19 positivity in BCG vaccinated versus unvaccinated was 0.79 (0.50-1.25). There was also a significant negative correlation between two groups. The relative risk of COVID-19 positivity in those with a BCG scar was 0.63 (0.44-0.92). The relative risk of COVID-19 infection in those with a history of tuberculosis was 1.08 (0.56-2.09).

Conclusion

The present study did not support the beneficial effect of BCG vaccine in protection against the development of COVID-19 disease.

SARS-CoV-2 infection in India bucks the trend: Trained innate immunity?

SARS-CoV-2, the causative agent of COVID-19 pandemic caught the world unawares by its sudden onset in early 2020. Memories of the 1918 Spanish Flu were rekindled raising extreme fear for the virus, but in essence, it was the host and not the virus, which was deciding the outcome of the infection. Age, gender, and preexisting conditions played critical roles in shaping COVID-19 outcome. People of lower socioeconomic strata were disproportionately affected in industrialized countries such as the United States. India, a developing country with more than 1.3 billion population, a large proportion of it being underprivileged and with substandard public health provider infrastructure, feared for the worst outcome given the sheer size and density of its population. Six months into the pandemic, a comparison of COVID-19 morbidity and mortality data between India, the United States, and several European countries, reveal interesting trends. While most developed countries show curves expected for a fast-spreading respiratory virus, India seems to have a slower trajectory. As a consequence, India may have gained on two fronts: the spread of the infection is unusually prolonged, thus leading to a curve that is "naturally flattened"; concomitantly the mortality rate, which is a reflection of the severity of the disease has been relatively low. I hypothesize that trained innate immunity, a new concept in immunology, may be the phenomenon behind this. Biocultural, socioecological, and socioeconomic determinants seem to be influencing the outcome of COVID-19 in different regions/countries of the world.

BCG vaccination at birth and COVID-19: a case-control study among U.S. military Veterans

In the early stages of the COVID-19 global pandemic, caused by the SARS-CoV-2 virus, low- and middle-income countries (LMICs) appeared to be experiencing lower morbidity and mortality rates than high-income countries, particularly the United States. Various suggestions put forward to account for this included the possibility that LMICs might be experiencing off-target benefits of infant vaccination with BCG, intended primarily to protect against tuberculosis. A number of ecologic epidemiological studies that considered COVID-19 morbidity and mortality rates across countries appeared to support this suggestion. Ecologic studies, however, are primarily hypothesis-generating, given their well-known limitations in extrapolating to the individual-person level. The present study, which employed anonymized records of U.S. Military Veterans treated by the Department of Veterans Affairs was principally a case-control study of COVID-19 infections with a retrospective cohort study of mortality nested within the infections. Controls were a random sample of Veterans not recorded as having had COVID-19. There were 263,039 controls and 167,664 COVID-19 cases, of whom 5,016 died. The combination of country and year of birth was used as a surrogate for infant BCG vaccination. The study did not support the hypothesis that BCG in infancy was protective against COVID-19. The odds ratio for infection was 1.07 (95% confidence interval [CI]: 1.03, 1.11) and the risk ratio for mortality among the COVID-19 cases was 0.86 (95% CI: 0.63, 1.18). The potential for non-differential exposure misclassification was a concern, possibly biasing measures of association toward the null value.

Low- and middle-income countries (LMICs) have appeared to be much less affected by the COVID-19 pandemic, caused by the SARS-CoV-2 virus, than might have been expected from the effects of the virus in more-developed countries. It has been suggested that BCG vaccination of infants against tuberculosis in LMICs might be providing cross-protection against COVID-19. BCG has never been routinely administered in the United States and is not currently administered in most other developed countries.

Some epidemiology studies, known as “ecologic” studies have provided support for the idea that BCG is protecting against COVID-19. However, ecologic studies, with group (i.e., country) measures of exposure and health outcomes, are difficult to interpret in terms of cause and effect.

More interpretable are studies that use individual-person measures of exposure and health outcome. We carried out such a study using data from several hundred-thousand U.S. military Veterans, many of whom were born in LMICs and would have received BCG vaccination as infants. Many U.S. Veterans have had COVID-19, and many of those have died of it.

Our study, the first of its kind, found no evidence to support the idea that infant BCG vaccination protects against infection or death from COVID-19.

COVID-19 and Beyond: Exploring Public Health Benefits from Non-Specific Effects of BCG Vaccination

Bacille Calmette–Guérin (BCG) vaccination, widely used throughout the world to protect against infant tuberculous meningitis and miliary tuberculosis (TB), can provide broad non-specific protection against infectious respiratory diseases in certain groups. Interest in BCG has seen a resurgence within the scientific community as the mechanisms for non-specific protection have begun to be elucidated. The impact of the COVID-19 pandemic on nearly every aspect of society has profoundly illustrated the pressure that respiratory infections can place on a national healthcare system, further renewing interest in BCG vaccination as a public health policy to reduce the burden of those illnesses. However, the United States does not recommend BCG vaccination due to its variable effectiveness against adult TB, the relatively low risk of Mycobacterium tuberculosis infection in most of the United States, and the vaccine’s interference with tuberculin skin test reactivity that complicates TB screening. In this review, we explore the broad immune training effects of BCG vaccination and literature on the effects of BCG vaccination on COVID-19 spread, disease severity, and mortality. We further discuss barriers to scheduled BCG vaccination in the United States and how those barriers could potentially be overcome.

100 years of Bacillus Calmette-Guérin immunotherapy: from cattle to COVID-19

Bacillus Calmette-Guérin (BCG) is the most widely used vaccine worldwide and has been used to prevent tuberculosis for a century. BCG also stimulates an anti-tumour immune response, which urologists have harnessed for the treatment of non-muscle-invasive bladder cancer. A growing body of evidence indicates that BCG offers protection against various non-mycobacterial and viral infections. The non-specific effects of BCG occur via the induction of trained immunity and form the basis for the hypothesis that BCG vaccination could be used to protect against the severity of coronavirus disease 2019 (COVID-19). This Perspective article highlights key milestones in the 100-year history of BCG and projects its potential role in the COVID-19 pandemic.

Racing to immunity: Journey to a COVID-19 vaccine and lessons for the future

SARS-CoV-2 is the novel coronavirus behind the COVID-19 pandemic. Since its emergence, the global scientific community has mobilized to study this virus, and an overwhelming effort to identify COVID-19 treatments is currently ongoing for a variety of therapeutics and prophylactics. To better understand these efforts, we compiled a list of all COVID-19 vaccines undergoing preclinical and clinical testing using the WHO and ClinicalTrials.gov database, with details surrounding trial design and location. The most advanced vaccines are discussed in more detail, with a focus on their technology, advantages and disadvantages, as well as any available recent clinical findings. We also cover some of the primary challenges, safety concerns and public responses to COVID-19 vaccine trials, and consider what this can mean for the future. By compiling this information, we aim to facilitate a more thorough understanding of the extensive COVID-19 clinical testing vaccine landscape as it unfolds, and better highlight some of the complexities and challenges being faced by the joint effort of the scientific community in finding a prophylactic against COVID-19.

Immunological parameters associated with the severity of COVID-19 pneumonia in kidney transplant recipients

Purpose

An outbreak of a novel respiratory disease due to coronavirus species was emerged in 2019 and named as Coronavirus Disease-2019 (COVID-19). Clinical and immunological factors affecting the course of COVID-19 in kidney transplant recipients (KTR) are not well-known.

Methods

In this prospective observational study, we presented 20 KTR with COVID-19 pnemonia and examined the factors predicting the severity of COVID-19. A total of 10 KTR without COVID-19 was used as control group. Lymphocyte subsets were determined by flow cytometry. In 13/20 patients, immunophenotyping was repeated 1 week later.

Results

Mean age of the patients was 50 ± 9 years. Patients were classified as mild–moderate (oxygen saturation: SO₂ > 90%) and severe disease groups (SO₂ ≤ 90%). Serum albumin and hemoglobin were lower and CRP, fibrinogen and peak d-dimer were higher in severe group. Peak CRP was inversely associated with nadir SO₂ (r =  − 0.68, p = 0.001). Neutrophil/lymphocyte ratio was higher in severe group (p = 0.01). CD3 + and CD4 + cells were lower and NK cell percentage (CD16 + 56 +) was higher in severe group. Percentage of spontaneously activated CD8 cells (CD8 + CD69 +) was higher in severe group. In comparison of KTR with and without COVID-19, CD8 + cells were lower but NK cell percentage was higher in KTR with COVID-19.

Conclusion

In this pilot study, increased NK cells, activated CD8 + cells and decreased CD3 + and CD4 + cells were associated with severity of COVID-19 in KTR. Peripheral immunophenotyping of lymphocyte subtypes may provide prognostic information about the clinical course of COVID-19 in KTR.

Supplementary Information

The online version contains supplementary material available at 10.1007/s11255-021-02947-y.

Repurposing of the childhood vaccines: could we train the immune system against the SARS-CoV-2

INTRODUCTION

The COVID-19 pandemic is a globalized health concern caused by a beta-coronavirus named Severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2). Since December 2019, when this outbreak flared in Wuhan, China, COVID-19 cases have been continuously rising all over the world. Due to the emergence of SARS-CoV-2 mutants, subsequent waves are flowing in a faster manner as compared to the primary wave, which is more contagious and causing higher mortality. Recently, India has emerged as the new epicenter of the second wave by mutants of SARS-CoV-2. After almost eighteen months of this outbreak, some COVID-19 dedicated therapeutics and vaccines are available, and a few are under trial, but the situation is still uncontrolled.

AREA COVERED

This perspective article covers the repurposing of childhood vaccines like Bacille Calmette-Guerin (BCG), Measles, Mumps, Rubella (MMR), and Oral Polio Vaccine (OPV), which are live attenuated vaccines and have been shown the protective effect through 'trained immunity and 'crossreactivity.'

EXPERT OPINION

This perspective article has suggested that combinatorial use of these childhood vaccines might exert a better protective effect along with the available COVID-19 therapeutic and vaccines which could be considered as a preventive option against SARS-CoV-2 infection as well as its subsequent waves.

A case control study to assess effectiveness of measles containing vaccines in preventing severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection in children

Currently, most licensed vaccines against SARS-CoV-2 infection are approved for adults and not for children. We conducted a test negative case-control study to assess the effectiveness of Measles Containing Vaccines (MCVs) against SARS-CoV-2 infection in Pune, India, in children who were ≥1 year and <18 years of age and were tested for SARS-CoV-2 infection by Reverse transcription polymerase chain reaction (RT-PCR). The enrolled participants included 274 SARS-CoV-2 positive cases (216 vaccinated and 58 unvaccinated) along with 274 SARS-CoV-2 negative controls (265 vaccinated and 9 unvaccinated). Of the 274 cases, 180 (65.7%) were asymptomatic while 94 (34.3%) were symptomatic, all with mild severity. The number of participants with symptomatic SARS-CoV-2 infection was significantly lower in the vaccinated group compared to the unvaccinated group (p < .0001). The unadjusted overall Vaccine Effectiveness (VE) in the vaccinated group compared to unvaccinated group was 87.4% (OR = 0.126, 95% CI of VE: 73.9-93.9) while the adjusted overall VE after adjusting for age and sex was 87.5% (OR = 0.125, 95% CI of VE: 74.2-94.0). MCVs reduced incidence of laboratory confirmed SARS-CoV-2 infection in children. Number of symptomatic cases were also lower in the vaccinated group compared to the unvaccinated group. Results of our study have provided strong preliminary evidence that MCVs have a good effectiveness against SARS-CoV-2 infection in the pediatric population, which needs to be confirmed further through prospective randomized clinical trials.

Bovine ownership and reduced pulmonary tuberculosis risk in Nepal: A case-control study

This case-control study sought to confirm and investigate in more depth protective associations previously found of bovine (cattle and water buffalo) ownership with reduced risk of both pulmonary tuberculosis (PTB) and latent tuberculosis infection (LTBI) in humans. The study recruited male and female PTB cases from a diagnostic centre and a frequency-matched community-based control group in Kaski District, Nepal. Controls were tested for LTBI status and a separate nested case-control study was conducted based on LTBI status. Data were collected on participant household animal ownership. Using logistic regression, animal ownership was investigated for associations with both PTB and LTBI. Data were obtained from 570 PTB cases and 1,224 controls, the latter group providing 396 LTBI-positive and 692 LTBI-negative subjects. Results provided evidence of decreased odds of both PTB and LTBI positivity associated with owning bovines. The evidence was strongest for protection against infection, rather than activation of infection to PTB. Effects were strongest in women, who usually manage the animals in Nepal, and there were exposure-response relationships with numbers of bovines owned. Results suggest that exposure to bovines is protective against LTBI and PTB. A possible mechanism involves boosting the effect of BCG (Bacillus Calmette-Guerin) vaccination, particularly in protecting against tuberculous infection. Additional studies with more extensive data collection are needed to confirm the observed associations.

Bacille Calmette-Guérin Vaccination in Infancy Does Not Protect Against Coronavirus Disease 2019 (COVID-19): Evidence From a Natural Experiment in Sweden

BACKGROUND

The bacille Calmette-Guérin (BCG) tuberculosis vaccine has immunity benefits against respiratory infections. Accordingly, it has been hypothesized to have a protective effect against coronavirus disease 2019 (COVID-19). Recent research found that countries with universal BCG childhood vaccination policies tend to be less affected by the COVID-19 pandemic. However, such ecological studies are biased by numerous confounders. Instead, this paper reports on a rare nationwide natural experiment that occurred in Sweden in 1975, where discontinuation of newborns' BCG vaccination led to a dramatic decrease in BCG coverage rate, thus allowing us to estimate BCG's effect without the biases associated with cross-country comparisons.

METHODS

Numbers of COVID-19 cases and hospitalizations were recorded for birth cohorts born just before and just after 1975, representing 1 026 304 and 1 018 544 individuals, respectively. We used regression discontinuity to assess the effect of BCG vaccination on COVID-19-related outcomes. On such a large population, this method allows for a precision that would be hard to achieve using a randomized controlled trial.

RESULTS

The odds ratios (95% CI) for COVID-19 cases and COVID-19-related hospitalizations were 1.0005 (.8130-1.1881) and 1.2046 (.7532-1.6560), allowing us to reject fairly modest effects of universal BCG vaccination. We can reject with 95% confidence that universal BCG vaccination reduces the number of cases by 19% and the number of hospitalizations by 25%.

CONCLUSIONS

While the effect of a recent vaccination must be evaluated, we provide strong evidence that receiving the BCG vaccine at birth does not have a protective effect against COVID-19 among middle-aged individuals.

Tuberculosis vaccine BCG: the magical effect of the old vaccine in the fight against the COVID-19 pandemic

Bacillus Calmette-Guérin (BCG) is a live attenuated M. bovis vaccine that was developed about 100 years ago by Albert Calmette and Camille Guérin. Many countries have been using the vaccine for decades against tuberculosis (TB). The World Health Organization (WHO) recommends a single dose of BCG for infants in TB endemic as well as leprosy high risk countries, and globally almost 130 million infants are vaccinated yearly. The role of BCG is well known in reducing neonatal and childhood death rates. Epidemiological and retrospective cross-sectional studies demonstrated that the BCG vaccination protects the children against respiratory tract infections and lowers the risk of malaria in children. In addition, BCG enhances IFN-γ and IL-10 levels, thus providing immunity against respiratory tract infection even in elderly people. The BCG is also known to provide nonspecific innate immunity against viruses and parasites, through an innate immune mechanism termed ‘trained immunity’ and is defined as the immunological recall of the innate immune system by epigenetic reprogramming. Based on these studies it is suggested that the BCG has the potential to act as a protective agent against COVID-19. Further proven safety records of BCG in humans, its adjuvant activity and low-cost manufacturing make it an attractive option to stop the pandemic and reduce the COVID-19 related mortality. In this review we discuss the heterologous effects of BCG, induction of trained immunity and its implication in development of a potential vaccine against COVID-19 pandemic.

A Survey Among Italian Physicians During COVID-19 Outbreak. Could Bacillus Calmette-Guérin Vaccine Be Effective Against SARS-CoV2?

Background: Epidemiological studies show that BCG-vaccinated population seems to be more likely protected from COVID-19 infection, but WHO gave a stark warning on use of BCG vaccine without confirmed COVID-19 trials. The aim of the study is to evaluate whether TB vaccination, performed several years earlier, could confer protection against COVID-19.

Methods: After the Ethical Committee authorization, professional orders were used to contact physicians with an online survey. Specialty, COVID-19 infection and previous BCG vaccination were recorded. Statistical data analysis was performed.

Results: 1906 physicians answered the questionnaire, (M = 1068; F = 838; mean age 50.7 ± 13.3 years; range 24–87), more than half (1062; 55.7%) experienced BCG vaccination. Professional activity was recorded, and only 49 subjects (2.6%) of them were infected by SARS-CoV2. Among the group of infected people, asymptomatic form occurred in 12 subjects (24.5%); a pauci-symptomatic form in 24 subjects (49.0%); and a severe form (pneumonia and/or respiratory distress) in 13 (26.5%). Considering only the clinically relevant form of COVID-19, period prevalence was 2.2% (23/1062) in the vaccinated group and 1.7% (14/844) in the unvaccinated group (OR: 1.31, 95% C.I.: 0.68–2.63, p = 0.427).

Conclusion: Our experience does not confirm the possible protective role of BCG vaccination, performed years earlier, against COVID-19. Although recent epidemiological studies point out in BCG-vaccinated population a lower prevalence of SARS-CoV2 infection, in our cohort of physicians no significant difference was found in terms of prevalence of COVID-19 infection. Our data underline the necessity to follow the WHO warning about the indiscriminate use of BCG vaccine, until clear evidence of protection by BCG vaccination against COVID-19 is fully demonstrated.

Countries with high deaths due to flu and tuberculosis demonstrate lower COVID-19 mortality: roles of vaccinations

Deaths due to the ongoing COVID-19 pandemic vary (3-1681 deaths/million and mortality rates 0.71-14.54%) and are far greater in some countries compared to others. This observation led us to perform epidemiological analysis, using data in the public domain, to study the correlation of COVID-19 with the prevalence and vaccination strategies for two respiratory pathogens: flu and tuberculosis (TB). Countries showing more than 1000 COVID-19 deaths were selected at three time points during the ongoing pandemic: 17 May, 1 October and 31 December 2020. The major findings of this study that are broadly consistent at all three time points are: First, countries with high flu deaths negatively correlate with COVID-19 deaths/million. Second, TB incidences and deaths negatively correlate with COVID-19 deaths/million. Countries displaying high TB and flu deaths (Nigeria, Ethiopia, Myanmar, Indonesia, India) display lower COVID-19 deaths/million compared to countries with low TB and flu deaths (Italy, Spain, USA, France). Third, countries with greater flu vaccination display lower flu incidences but higher COVID-19 deaths/million and mortality rates. On the other hand, Bacillus Calmette Guerin (BCG) vaccination negatively correlates with Covid-19 deaths/million. Fourth, countries with only BCG, but no flu, vaccination show delayed and lower number of COVID-19 deaths/million compared to countries with flu, but no BCG, vaccination. Fifth, countries with high BCG vaccination coverage as well as high TB deaths display the lowest COVID-19 deaths/million. The implications of this global study are discussed with respect to the roles of respiratory infections and vaccinations in lowering COVID-19 deaths.

Protective role of intravesical BCG in COVID-19 severity

OBJECTIVES

To establish the role of BCG instillations in the incidence and mortality of COVID-19.

PATIENTS AND METHODS

NMIBC patients in instillations with BCG (induction or maintenance) during 2019/2020 were included, establishing a COVID-19 group (with a diagnosis according to the national registry) and a control group (NO-COVID). The cumulative incidence (cases/total patients) and the case fatality rate (deaths/cases) were established, and compared with the national statistics for the same age group. T-test was used for continuous variables and Fisher's exact test for categorical variables.

RESULTS

175 patients were included. Eleven patients presented CIS (11/175, 6.3%), 84/175 (48.0%) Ta and 68/175 (38.9%) T1. Average number of instillations = 13.25 ± 7.4. One hundred sixty-seven patients (95.4%) had complete induction. Forty-three patients (cumulative incidence 24.6%) were diagnosed with COVID-19. There is no difference between COVID-19 and NO-COVID group in age, gender or proportion of maintenance completed. COVID-19 group fatality rate = 1/43 (2.3%). Accumulated Chilean incidence 70-79 years = 6.3%. Chilean fatality rate 70-79 years = 14%.

CONCLUSIONS

According to our results, patients with NMIBC submitted to instillations with BCG have a lower case-fatality rate than the national registry of patients between 70 and 79 years (2.3% vs. 14%, respectively). Intravesical BCG could decrease the mortality due to COVID-19, so instillation schemes should not be suspended in a pandemic.

The BCG Vaccine for COVID-19: First Verdict and Future Directions

Despite of the rapid development of the vaccines against the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), it will take several months to have enough doses and the proper infrastructure to vaccinate a good proportion of the world population. In this interim, the accessibility to the Bacille Calmette-Guerin (BCG) may mitigate the pandemic impact in some countries and the BCG vaccine offers significant advantages and flexibility in the way clinical vaccines are administered. BCG vaccination is a highly cost-effective intervention against tuberculosis (TB) and many low-and lower-middle-income countries would likely have the infrastructure, and health care personnel sufficiently familiar with the conventional TB vaccine to mount full-scale efforts to administer novel BCG-based vaccine for COVID-19. This suggests the potential for BCG to overcome future barriers to vaccine roll-out in the countries where health systems are fragile and where the effects of this new coronavirus could be catastrophic. Many studies have reported cross-protective effects of the BCG vaccine toward non-tuberculosis related diseases. Mechanistically, this cross-protective effect of the BCG vaccine can be explained, in part, by trained immunity, a recently discovered program of innate immune memory, which is characterized by non-permanent epigenetic reprogramming of macrophages that leads to increased inflammatory cytokine production and consequently potent immune responses. In this review, we summarize recent work highlighting the potential use of BCG for the treatment respiratory infectious diseases and ongoing SARS-CoV-2 clinical trials. In situations where no other specific prophylactic tools are available, the BCG vaccine could be used as a potential adjuvant, to decrease sickness of SARS-CoV-2 infection and/or to mitigate the effects of concurrent respiratory infections.

COVID-19 pandemic: Practical considerations on the organization of an allergy clinic-An EAACI/ARIA Position Paper

BACKGROUND

The coronavirus disease 2019 (COVID-19) has evolved into a pandemic infectious disease transmitted by the severe acute respiratory syndrome coronavirus (SARS-CoV-2). Allergists and other healthcare providers (HCPs) in the field of allergies and associated airway diseases are on the front line, taking care of patients potentially infected with SARS-CoV-2. Hence, strategies and practices to minimize risks of infection for both HCPs and treated patients have to be developed and followed by allergy clinics.

METHOD

The scientific information on COVID-19 was analysed by a literature search in MEDLINE, PubMed, the National and International Guidelines from the European Academy of Allergy and Clinical Immunology (EAACI), the Cochrane Library, and the internet.

RESULTS

Based on the diagnostic and treatment standards developed by EAACI, on international information regarding COVID-19, on guidelines of the World Health Organization (WHO) and other international organizations, and on previous experience, a panel of experts including clinicians, psychologists, IT experts, and basic scientists along with EAACI and the "Allergic Rhinitis and its Impact on Asthma (ARIA)" initiative have developed recommendations for the optimal management of allergy clinics during the current COVID-19 pandemic. These recommendations are grouped into nine sections on different relevant aspects for the care of patients with allergies.

CONCLUSIONS

This international Position Paper provides recommendations on operational plans and procedures to maintain high standards in the daily clinical care of allergic patients while ensuring the necessary safety measures in the current COVID-19 pandemic.

T-Helper Cell Subset Response Is a Determining Factor in COVID-19 Progression

The immune response type organized against viral infection is determinant in the prognosis of some infections. This work has aimed to study Th polarization in acute COVID-19 and its possible association with the outcome through an observational prospective study. Fifty-eight COVID-19 patients were recruited in the Medicine Department of the hospital “12 de Octubre,” 55 patients remaining after losses to follow-up. Four groups were established according to maximum degree of disease progression. T-helper cell percentages and phenotypes, analyzed by flow cytometer, and serum cytokines levels, analyzed by Luminex, were evaluated when the microbiological diagnosis (acute phase) of the disease was obtained. Our study found a significant reduction of %Th1 and %Th17 cells with higher activated %Th2 cells in the COVID-19 patients compared with reference population. A higher percent of senescent Th2 cells was found in the patients who died than in those who survived. Senescent Th2 cell percentage was an independent risk factor for death (OR: 13.88) accompanied by the numbers of total lymphocytes (OR: 0.15) with an AUC of 0.879. COVID-19 patients showed a profile of pro-inflammatory serum cytokines compared to controls, with higher levels of IL-2, IL-6, IL-15, and IP-10. IL-10 and IL-13 were also elevated in patients compared to controls. Patients who did not survive presented significantly higher levels of IL-15 than those who recovered. No significant differences were observed according to disease progression groups. The study has shown that increased levels of IL-15 and a high Th2 response are associated with a fatal outcome of the disease.

Current State of the First COVID-19 Vaccines

SARS CoV-2 and its associated disease COVID-19 has devastated the world during 2020. Masks and social distancing could be efficient if done by large proportions of the population, but pandemic fatigue has decreased their efficacy. Economic shut downs come with large price tags and cannot be a long term solution either. The announcements by three vaccine manufacturers in November that their vaccines are 90% or more effective has given hope to at least those in the population who plan to get vaccinated as soon as a scientifically and medically sound vaccine becomes available. This review summarizes the underlying design strategies and current status of development of the nine vaccines that were in phase III trial on 8 November 2020. Contracts between vaccine manufacturing companies and governments aim at distributing the vaccine to a large part of the world population. Questions remain how the temperature sensitive mRNA vaccines will be transported and/or stored and how vaccination will be prioritized within each country. Additionally, current contracts do not cover all countries, with a serious gap in Africa and South America. The second part of this review will detail current distribution plans and remaining challenges with vaccine accessibility and acceptance.

Does bacille calmette–Guérin vaccination provides protection against COVID-19: A systematic review and meta-analysis

Background:

Lower morbidity and mortality in few geographic locations on the globe suffering with SARS-CoV-2 has been associated with the existing or previously followed long-standing Bacille Calmette–Guérin (BCG) vaccination policy among infants. However, does it hold true that today after years of BCG vaccination, few adults have better prognosis or is it just confounding due to differential disease burden, population density, testing facilities, or improper reporting. The purpose was to evaluate and correlate this effect systematically.

Methods:

Detailed electronic search for randomized controlled trials (RCTs) and observational studies in PubMed, Cochrane Library, and ClinicalTrials.gov for eligible studies was performed.

Results:

One hundred and fourteen studies were yielded on search strategy and 28 observational studies were finally included for analysis. From our results, we can say that BCG vaccination causes a decrease in COVID-19 incidence and mortality. However, these results must be interpreted cautiously as lot of confounding factors were present in included studies, which can affect the outcome.

Conclusion:

The evidence of BCG vaccination for the protection against COVID-19 cannot be ruled out as evidence from many studies support the hypothesis, but the evidence of well-conducted RCTs and observational studies can strengthen the evidence.

Registration Number:

PROSPERO (International Prospective Register of Systematic Reviews) database (CRD42020204466).

BCG vaccination induced protection from COVID-19

There are worldwide urgency, efforts, and uncertainties for the discovery of a vaccine against SARS CoV2. If successful, it will take its own time till useful for the humans. Till the specific vaccine is available, there are evidences for repurposing existing other vaccines. It is observed that countries having a routine BCG vaccination programme, have shown to have lower incidence of COVID-19, suggesting some protective mechanisms of BCG against COVID-19 in such countries. In countries like India despite vast population density and other adversities, and growing numbers of COVID19 infections, the mortality rate and severity of COVID has been low in comparison to some TB non-endemic countries (like Europe and USA). In addition, there are evidences that BCG vaccination offers partial protection and survival in low-income countries where tuberculosis is prevalent. The nonspecific effects (NSEs) of immune responses induced by BCG vaccination protect against other infections seem to be due to its immunological memory eliciting lymphocytes response and trained immunity. The protective effect on other viral infection in humans are believed to be mediated by heterologous lymphocyte activation and the initiation of innate immune memory may be applicable to SARS CoV2. The BCG vaccination at birth does not have a protective effect beyond childhood against COVID-19. In adults, there might be other factors dampening the virulence and pathogenicity of COVID-19. In the TB endemic countries like India, with high population density, similar to BCG vaccination, the environmental Mycobacteria might be imparting some immune-protection from severity and deaths of COVID-19.

T Cells: Warriors of SARS-CoV-2 Infection

Severe infection with severe acute respiratory syndrome coronavirus (SARS-CoV)-2 is characterized by massive cytokine release and T cell loss. The exaggerated host immune response, incapable of viral clearance, instead aggravates respiratory distress, as well as cardiac, and/or damage to other organs. The mortality pattern of SARS-CoV-2 infection, higher in older versus younger adults and almost absent in children, is possibly caused by the effects of age and pre-existing comorbidities on innate and adaptive immunity. Here, we speculate that the abnormal and excessive immune response to SARS-CoV-2 infection partly depends on T cell immunological memory, which is more pronounced in adults compared with children, and may significantly contribute to immunopathology and massive collateral damage in coronavirus disease 2019 (COVID-19) patients.

Trained immunity as a novel approach against COVID-19 with a focus on Bacillus Calmette-Guérin vaccine: mechanisms, challenges and perspectives

COVID-19 is a severe health problem in many countries and has altered day-to-day life in the whole world. This infection is caused by the SARS-CoV-2 virus, and depending on age, sex and health status of the patient, it can present with variety of clinical symptoms such as mild infection, a very severe form or even asymptomatic course of the disease. Similarly to other viruses, innate immune response plays a vital role in protection against COVID-19. However, dysregulation of innate immunity could have a significant influence on the severity of the disease. Despite various efforts, there is no effective vaccine against the disease so far. Recent data have demonstrated that the Bacillus Calmette-Guérin (BCG) vaccine could reduce disease severity and the burden of several infectious diseases in addition to targeting its primary focus tuberculosis. There is growing evidence for the concept of beneficial non-specific boosting of immune responses by BCG or other microbial compounds termed trained immunity, which may protect against COVID-19. In this manuscript, we review data on how the development of innate immune memory due to microbial compounds specifically BCG can result in protection against SARS-CoV-2 infection. We also discuss possible mechanisms, challenges and perspectives of using innate immunity as an approach to reduce COVID-19 severity.

[BCG, muramylpeptides, trained immunity (part I): linkages in the light of the COVID-19 pandemic]

It has long been known that Bacillus CalmetteGurin (BCG) vaccine provides nonspecific protection against many non-mycobacterial infections, which has been discussed in the last decade through the prism of the concept of trained immunity. Within the framework of this concept, a persistent increase in resistance to various pathogens, which occurs after an infectious disease or exposure to certain microbial agents, is associated with epigenetic reprogramming of innate immune cells and their bone marrow progenitors. The COVID-19 pandemic has drawn attention of scientists and practitioners to BCG as an inducer of trained immunity. A number of epidemiological studies have suggested a negative association between the coverage of the population with BCG vaccination and the burden of SARS-CoV-2 infection. A series of independent clinical studies of the effectiveness of this vaccine in non-specific prevention of COVID-19 has been initiated in different countries. Recently, the key role of cytosolic NOD2 receptors in BCG-induced trained immunity has been proven. This actualizes the search for effective immunoactive preparations for prevention of respiratory infections in the pandemic among low molecular weight peptidoglycan fragments of the bacterial cell wall, muramylpeptides (MPs), which are known to be NOD2 agonists. The review highlights the proven and proposed linkages between BCG, MPs, NOD2 and trained immunity in the light of the COVID-19 pandemic. Analysis of the data presented indicates the prospects for preclinical and clinical studies of MPs as potential drugs for nonspecific prevention of SARS-CoV-2 infection and/or other respiratory infections in risk groups during the pandemic. First of all, attention should be paid to glucosaminylmuramyl dipeptide, approved for clinical use in Russia and a number of post-Soviet countries for the complex treatment and prevention of acute and recurrent respiratory infections.

On the relationship between BCG coverage and national COVID-19 outcome: could 'heterologous' herd immunity explain why some countries are better off?

The COVID-19 pandemic has affected most parts of the global society since its emergence, and the scientific community has been challenged with questions urgently demanding answers. One of the early hypotheses on COVID-19 outcome was that some protection could be offered by the tuberculosis vaccine (BCG), and several clinical studies were initiated along with the emergence of numerous observational studies on the relationship between BCG and COVID-19 severity. In the present work, I demonstrate a strong correlation between the number of years that countries implemented BCG vaccination plans and age-standardized mortality rates during the first months of the pandemic in Europe. Further analyses of age groups in two European countries with comparably few confounding factors and easily identifiable groups of BCG-vaccinated and non-vaccinated subgroups suggest a population-level effect of BCG on national outcomes of COVID-19. This phenomenon of 'heterologous herd immunity' deserves further investigation, both in epidemiological and experimental studies.

COVID-19 vaccine development: What lessons can we learn from TB?

At the time of writing, the SARS-CoV-2 virus has infected more than 49 million people causing more than 1.2 million deaths worldwide since its emergence from Wuhan, China in December 2019. Vaccine development against SARS-CoV-2 has drawn the global attention in order to stop the spread of the virus, with more than 10 vaccines being tested in phase III clinical trials, as of November 2020. However, critical to vaccine development is consideration of the immunological response elicited as well as biological features of the vaccine and both need to be evaluated thoroughly. Tuberculosis is also a major infectious respiratory disease of worldwide prevalence and the vaccine development for tuberculosis has been ongoing for decades. In this review, we highlight some of the common features, challenges and complications in tuberculosis vaccine development, which may also be relevant for, and inform, COVID-19 vaccine development.

The challenge of concomitant infections in the coronavirus disease 2019 pandemic era: Severe acute respiratory syndrome coronavirus 2 infection in a patient with chronic Chagas disease and dimorphic leprosy

Coronavirus disease 2019 (COVID-19) was first officially described in Brazil on February 26^th, 2020. The accumulation of reports of concomitant infections with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and pathogens that cause diseases endemic to tropical countries, such as dengue and chikungunya fever, has started to draw attention. Chagas disease and leprosy remain public health problems in many developing countries, such as Brazil. In this manuscript, we describe a case of concomitant leprosy, Chagas disease, and COVID-19, highlighting the cutaneous manifestations of SARS-CoV-2 infection and the clinical behavior of household contacts who previously received prophylactic Bacillus Calmette-Guérin vaccines.

BCG vaccination early in life does not improve COVID-19 outcome of elderly populations, based on nationally reported data

The reported numbers of Covid-19 cases and deaths were compared for 18 countries (14 in Western Europe, plus Australia, Brazil, Israel and the USA) to assess the effect of historic and current national BCG immunizations. In view of the high death rate for Covid-19 patients over 70 years of age, and given the fact that BCG vaccination is typically given early in life, we compared countries that had introduced BCG in the 1950s with those that had not. No effect on Covid-19 case fatality rate (CFR) or number of deaths per population could be demonstrated. Since some countries test for Covid-19 more than others, the effect of tests performed per million population on reported deaths per million was also assessed, but again did not demonstrate an effect of BCG vaccination in the 1950s. Whether countries had never used the vaccine, had historically used it but since ceased to do so, or were presently vaccinating with BCG did not correlate with national total number of deaths or CFR. We conclude that there is currently no evidence for a beneficial effect of BCG vaccination on Covid-19 reported cases or fatalities.

A Systems Biology Workflow for Drug and Vaccine Repurposing: Identifying Small-Molecule BCG Mimics to Reduce or Prevent COVID-19 Mortality

PURPOSE

Coronavirus disease 2019 (COVID-19) is expected to continue to cause worldwide fatalities until the World population develops 'herd immunity', or until a vaccine is developed and used as a prevention. Meanwhile, there is an urgent need to identify alternative means of antiviral defense. Bacillus Calmette-Guérin (BCG) vaccine that has been recognized for its off-target beneficial effects on the immune system can be exploited to boast immunity and protect from emerging novel viruses.

METHODS

We developed and employed a systems biology workflow capable of identifying small-molecule antiviral drugs and vaccines that can boast immunity and affect a wide variety of viral disease pathways to protect from the fatal consequences of emerging viruses.

RESULTS

Our analysis demonstrates that BCG vaccine affects the production and maturation of naïve T cells resulting in enhanced, long-lasting trained innate immune responses that can provide protection against novel viruses. We have identified small-molecule BCG mimics, including antiviral drugs such as raltegravir and lopinavir as high confidence hits. Strikingly, our top hits emetine and lopinavir were independently validated by recent experimental findings that these compounds inhibit the growth of SARS-CoV-2 in vitro.

CONCLUSIONS

Our results provide systems biology support for using BCG and small-molecule BCG mimics as putative vaccine and drug candidates against emergent viruses including SARS-CoV-2.

Immunology of COVID-19: Mechanisms, clinical outcome, diagnostics, and perspectives-A report of the European Academy of Allergy and Clinical Immunology (EAACI)

With the worldwide spread of the novel severe acute respiratory syndrome coronavirus‐2 (SARS‐CoV‐2) resulting in declaration of a pandemic by the World Health Organization (WHO) on March 11, 2020, the SARS‐CoV‐2‐induced coronavirus disease‐19 (COVID‐19) has become one of the main challenges of our times. The high infection rate and the severe disease course led to major safety and social restriction measures worldwide. There is an urgent need of unbiased expert knowledge guiding the development of efficient treatment and prevention strategies. This report summarizes current immunological data on mechanisms associated with the SARS‐CoV‐2 infection and COVID‐19 development and progression to the most severe forms. We characterize the differences between adequate innate and adaptive immune response in mild disease and the deep immune dysfunction in the severe multiorgan disease. The similarities of the human immune response to SARS‐CoV‐2 and the SARS‐CoV and MERS‐CoV are underlined. We also summarize known and potential SARS‐CoV‐2 receptors on epithelial barriers, immune cells, endothelium and clinically involved organs such as lung, gut, kidney, cardiovascular, and neuronal system. Finally, we discuss the known and potential mechanisms underlying the involvement of comorbidities, gender, and age in development of COVID‐19. Consequently, we highlight the knowledge gaps and urgent research requirements to provide a quick roadmap for ongoing and needed COVID‐19 studies.