Randomized Trial of BCG Vaccine to Protect against Covid-19 in Health Care Workers

Efficacy of BCG vaccination against COVID-19 in health care workers and non-health care workers: A meta-analysis of randomized controlled trials

BACKGROUND

The Bacillus Calmette-Guérin (BCG) vaccine has shown potential non-specific protection against infectious diseases through "trained immunity", which may offer cross-protection against viral infections. However, there is no consensus on whether BCG vaccination could prevent COVID-19 or reduce its symptoms.

METHODS

PubMed, Cochrane Library, Embase and Web of Science were searched for randomized controlled trials on BCG vaccination and COVID-19 prevention, covering studies from the inception of each database to 2 May 2024. We included studies where participants, not infected with COVID-19, were vaccinated with BCG or placebo. We excluded non-randomized trials, studies without full texts, unrelated interventions, and those not reporting relevant outcomes. Clinical data on COVID-19 infection, severity, hospitalization, mortality, and other adverse events, were extracted and analyzed. The DerSimonian-Laird random-effects model and the Cochrane Collaboration's risk of Bias Tool were used for analysis and risk of bias assessment.

RESULTS

A total of 12 RCTs involving 18,086 patients were finally included. For the prophylactic effect of BCG on COVID-19, pooled results showed no statistically significant difference between BCG and placebo (pooled RR 1.02; 95%CI: 0.91-1.14). There was no statistically significant difference between non-health care workers (pooled RR 0.91; 95%CI: 0.67-1.24) and health care workers (pooled RR 1.03; 95%CI: 0.93-1.15). Regarding COVID-19 severity, no significant difference were found for asymptomatic (pooled RR 1.18; 95%CI: 0.81-1.72), mild to moderate (pooled RR 0.99; 95%CI: 0.84-1.17), severe COVID-19 (pooled RR 1.25; 95%CI: 0.92-1.70), hospitalization (pooled RR 0.93; 95%CI: 0.58-1.50) or all-cause mortality (pooled RR 0.60; 95%CI: 0.18-1.95) between BCG and placebo groups. Subgroup analysis also showed no significant difference between BCG and placebo in non-health care workers or health care workers.

CONCLUSIONS

Vaccination of BCG could not effectively prevent COVID-19 infection or decrease COVID-19 symptoms both in non-health care workers and health care workers.

Individual- and population-associated heterogeneity in vaccine-induced immune responses. The impact of inflammatory status and diabetic comorbidity

Vaccines induce quantitively and qualitatively different effector responses between populations but also between individuals within populations. Several factors are known to affect the success of vaccination, including age, gender, co-infections (e.g. HIV), pre-existing inflammatory status and co-morbidities such as type 2 diabetes mellitus (T2DM). These factors, either alone or in combination, strongly influence vaccine induced immunity and thereby possibly vaccine efficacy. Vaccination strategies should therefore not only be evaluated in young, healthy selected individuals but also in individuals with immune ageing, persisting inflammation and co-morbidities, and include the measurement of qualitative rather than only quantitative measures of vaccine effects.

Efficacy of BCG vaccination on incidence, severity and clinical progression of COVID-19: A BCG-REVAC population analysis

BACKGROUND

Can vaccination with Bacille Calmette-Guérin prevent clinical progression of COVID-19? Data from the BCG-REVAC trial was archived in a database, creating an excellent opportunity to link it to notified cases of COVID-19 to evaluate the efficacy of BCG against incidence, severity and clinical progression to severe COVID-19 when given at birth day, at school age as a first dose or as a second dose.

METHODS

This study was conducted in the population of the BCG-REVAC cluster randomisation trial including 354,403 schoolchildren, aged 7 to 14 years, from 767 schools from two cities, Salvador and Manaus. Cases of COVID-19 from the System for Notification of Infectious Diseases and the System for Notification of Severe Respiratory Illnesses were record linked to BCG-REVAC population. The exposure was Vaccination or revaccination obtained by the BCG-REVAC. The outcomes of interest in this study were incidence COVID-19; incidence of severe COVID-19; and clinical progression of COVID-19. This project was approved by the Ethics Committee of the Institute of Collective Health, Federal University of Bahia, Brazil.

RESULTS

The neonatal dose and a first dose of BCG at school age protect against the incidence of severe COVID-19 in multivariate models, whose efficacies were 30 % (95 %CI:1-51) and 64 % (95 %CI: 22-84), respectively. The neonatal dose showed an effect on severe clinical progression of symptomatic COVID-19 disease in COVID-19 infected subjects 39 % (95 %CI:11 % - 58 %).

CONCLUSION

Even 23 years after BCG vaccination and revaccination of school-age children our results suggesting a protective effect of BCG first dose against incidence of severe COVID-19 in infected individuals, a smaller effect of the neonatal dose and no effect of the second dose at school age.

Prevalence of Long COVID in Mycobacterium tuberculosis-exposed Groups in Peru and Kenya

Background

Long COVID (LC), also referred to as post-COVID condition, refers to new or worsening symptoms lasting more than three months after SARS-CoV-2 infection. The prevalence of LC, and the impact of co-infection with prevalent pathogens such as Mycobacterium tuberculosis (Mtb), in low- and middle-income countries remain unclear. We aimed to address these gaps in two Mtb-exposed populations.

Methods

We recruited HIV-uninfected pulmonary tuberculosis (TB) patients (n=36) and their household contacts (n=63) in Peru, and healthcare workers (n=202) in Kenya. We collected clinical data using study instruments adapted from a United States based study of LC. Participants were sampled within 2 years of SARS-CoV-2 diagnosis.

Results

In Peru, 41.4% participants reported LC symptoms, with no TB-associated significant differences in the prevalence or clinical phenotypes of LC. The most common LC symptoms were neurological (e.g., headache and trouble sleeping) and musculoskeletal (e.g., back pain). Kenyan participants reported acute, but no LC symptoms, and reported a decline in the quality of life during acute infection. In Peru, the post-COVID-19 period was associated with a significant decline in all quality-of-life dimensions (p<0.01), except depression and anxiety (p=0.289).

Conclusion

This study shows that LC prevalence was high in Peru, where TB status was not linked to LC symptoms. Those with LC reported high levels of musculoskeletal and neurological symptoms. Unexpectedly, healthcare workers in Kenya denied the presence of LC symptoms. These findings highlight the need for long-term follow-up and larger studies in different geographic settings to dissect the impact of TB comorbidity on LC.

Deconvoluting the interplay of innate and adaptive immunity in BCG-induced nonspecific and TB-specific host resistance

BCG is the oldest vaccine in continuous use. While current intradermal vaccination regimens confer limited protection outside the context of pediatric extrapulmonary tuberculosis (TB), promising new data indicate that when administered mucosally or intravenously at a higher dose, BCG can induce sterilizing immunity against pulmonary TB in nonhuman primates. BCG is also known to promote nonspecific host resistance against a variety of unrelated infections and is a standard immunotherapy for bladder cancer, suggesting that this innate immune function may contribute to its protective role against TB. Here, we propose that both the mycobacterial-specific and off-target effects of BCG depend on the interplay of adaptive and innate cells and the cytokines they produce, and that the elucidation of this interaction should be a major strategy in the development of more effective BCG-based vaccines and immunotherapies.

Trained immunity-based mucosal immunotherapies for the prevention of respiratory infections

The devastating impact of respiratory infections demonstrates the critical need for novel prophylactic vaccines. In this opinion article, we advocate for bacterial immunotherapies as a complementary tool in our fight against respiratory infections. These immunotherapies can activate a wide spectrum of immunological mechanisms, with trained immunity (TI) being particularly significant. This phenomenon has led to the concept of trained immunity-based vaccines (TIbVs), which represent a novel approach in vaccinology. We discuss examples of TIbVs, including the tuberculosis vaccine Bacille Calmette-Guérin (BCG) and the polybacterial immunotherapy MV130. From our viewpoint, illustrating the mode of action and clinical evidence supports the proposal that TIbVs should be considered as next-generation vaccines to confer protection against a wide range of respiratory infections.

Randomized trial of BCG in healthcare workers to reduce absenteeism during the COVID-19 pandemic in sub-Saharan Africa

BACKGROUND

We tested whether providing BCG vaccine to healthcare workers (HCWs) could reduce non-planned absenteeism and thereby reduce the potential impact of the COVID-19 pandemic on healthcare systems in Africa.

METHODS

We conducted a multicenter, single-blinded, placebo-controlled randomized trial in Guinea-Bissau and Mozambique between December 2020 and June 2022. Participants were randomized 1:1 to BCG vaccine or placebo (saline) and followed by biweekly telephone calls for 6 mo. The incidence of unplanned absenteeism due to illness was analyzed using Bayesian negative binomial regression yielding relative RRs. Secondary outcomes included infectious disease episodes, COVID-19 infection and all-cause hospitalizations.

RESULTS

We enrolled 668 HCWs (Guinea-Bissau, n=503; Mozambique, n=165). The RR for absenteeism of BCG vs placebo was 1.29 (0.81 to 1.94) with comparable effects by country. No protection against infectious disease episodes (HR=1.18 [0.97 to 1.45]) or COVID-19 infection (HR=1.19 [0.80 to 1.75]) was observed. Two trial deaths (1 BCG, 1 control) were registered and nine admissions (3 BCG, 6 control), the all-cause admission HR being 0.51 (0.13 to 2.03).

CONCLUSIONS

With 64% of the planned sample size and unplanned absenteeism rates lower than expected, BCG did not reduce self-reported absenteeism due to illness. Rather, BCG tended to increase the risk of self-reported absenteeism, infectious disease episodes and COVID-19 infections.

SHORT SUMMARY

This was a randomized control trial assessing non-specific effects of BCG vaccination in healthcare workers. There was no beneficial effect on self-reported absenteeism due to illness within 6 mo of follow-up during the COVID-19 pandemic, but a trend towards fewer all-cause hospital admissions.

Efficacy of Bacille Calmette-Guérin Against COVID-19 Hospitalisation: A Meta-Analysis and Systematic Review of Randomised Control Trials

BACKGROUND

The BCG vaccine has long been hypothesised to have non-specific protective effects, and early epidemiological studies on COVID-19 suggested a possible protective effect against SARS-CoV-2 infection and COVID-19 severity. This systematic review and meta-analysis assesses the effect of the BCG vaccine on preventing severe COVID-19 disease, based on the rate of hospitalisation for COVID-19 related disease.

METHODS

We performed a literature search of randomised control trials comparing BCG vaccine to placebo in adult participants using EMBASE, MEDLINE, and Web of Science. A random effects model was used to generate summary estimates. Risk of bias was assessed regarding randomisation, allocation sequence concealment, blinding, incomplete outcome data, selective outcome reporting, and other biases.

RESULTS

We included 11 studies involving 18,412 participants, reporting COVID-19 incidence. The hospitalisation rate was sought from the authors of papers that did not report on this statistic. There was no significant reduction in COVID-19-related hospitalisation across all studies (relative risk 0.85, 0.51-1.40, p = 0.335), COVID-19 incidence across all studies (relative risk 1.07, 0.94-1.21, p = 0.264), deaths reported in six studies (relative risk 0.67, 0.36-1.26, p = 0.733), and COVID-19-related critical care admissions reported in four studies (relative risk 0.43, 0.13-1.46, p = 0.746).

CONCLUSIONS

The findings from this meta-analysis, involving a large number of participants, suggest no protective effect of BCG vaccination against severe COVID-19 outcomes or overall SARS-CoV-2 incidence. Further research may be needed to explore the potential non-specific effects of BCG vaccination in other specific populations and against other infections.

Characterising the SARS-CoV-2 nucleocapsid (N) protein antibody response

OBJECTIVES

SARS-CoV-2 nucleocapsid (N) protein antibodies can be used to identify the serological response to natural infection in those who have previously received a COVID-19 spike-based vaccine. Anti-N antibody responses can also be induced by inactivated whole SARS-CoV-2 virus vaccines, such as CoronaVac. We aimed to characterise antibody responses to the N protein following COVID-19 and following vaccination with CoronaVac.

METHODS

Using participants from an international randomised controlled trial, we investigated the evolution of anti-N antibody responses over time in two separate groups: adults following COVID-19, and in adults following vaccination with CoronaVac.

RESULTS

In 212 participants who had COVID-19, the anti-N seroconversion rate was 96.9% in those infected following an incomplete course of COVID-19 (spike-based) vaccinations and 88.2% in those infected following a complete course. Anti-N antibody indices were highly variable between participants, and higher in participants who had more severe COVID-19 symptoms, were aged ≥60 years, were unvaccinated, had comorbidities and those resident in Brazil. Most participants remained seropositive after 12 months. In 317 separate participants, the anti-N seroconversion rate was 63.5% following CoronaVac vaccination, with variable antibody indices.

CONCLUSIONS

Anti-N responses to COVID-19 and CoronaVac are highly variable but persistent. A prior complete course of COVID-19 spike-based vaccination reduced both anti-N seroconversion and antibody indices following COVID-19.

Effect of Bacille Calmette-Guérin vaccination on immune responses to SARS-CoV-2 and COVID-19 vaccination

Objectives

Bacille Calmette-Guérin (BCG) vaccination has off-target effects on disease risk for unrelated infections and immune responses to vaccines. This study aimed to determine the immunomodulatory effects of BCG vaccination on immune responses to vaccines against SARS-CoV-2.

Methods

Blood samples, from a subset of 275 SARS-CoV-2-naïve healthcare workers randomised to BCG vaccination (BCG group) or no BCG vaccination (Control group) in the BRACE trial, were collected before and 28 days after the primary course (two doses) of ChAdOx1-S (Oxford-AstraZeneca) or BNT162b2 (Pfizer-BioNTech) vaccination. SARS-CoV-2-specific antibodies were measured using ELISA and multiplex bead array, whole blood cytokine responses to γ-irradiated SARS-CoV-2 (iSARS) stimulation were measured by multiplex bead array, and SARS-CoV-2-specific T-cell responses were measured by activation-induced marker and intracellular cytokine staining assays.

Results

After randomisation (mean 11 months) but prior to COVID-19 vaccination, the BCG group had lower cytokine responses to iSARS stimulation than the Control group. After two doses of ChAdOx1-S, differences in iSARS-induced cytokine responses between the BCG group and Control group were found for three cytokines (CTACK, TRAIL and VEGF). No differences were found between the groups after BNT162b2 vaccination. There were also no differences between the BCG and Control groups in COVID-19 vaccine-induced antigen-specific antibody responses, T-cell activation or T-cell cytokine production.

Conclusion

BCG vaccination induced a broad and persistent reduction in ex vivo cytokine responses to SARS-CoV-2. Following COVID-19 vaccination, this effect was abrogated, and BCG vaccination did not influence adaptive immune responses to COVID-19 vaccine antigens.

An Update on Anti-COVID-19 Vaccines and the Challenges to Protect Against New SARS-CoV-2 Variants

The COVID-19 pandemic has posed a significant threat to global health systems, with extensive impacts across many sectors of society. The pandemic has been responsible for millions of deaths worldwide since its first identification in late 2019. Several actions have been taken to prevent the disease, including the unprecedented fast development and global vaccination campaigns, which were pivotal in reducing symptoms and deaths. Given the impact of the pandemic, the continuous changes of the virus, and present vaccine technologies, this review analyzes how, so far, we have met the challenge posed by the emergence of new variants and discusses how next-generation pan-coronavirus vaccines, with enhanced longevity and breadth of immune responses, may be tackled with alternative administration routes and antigen delivery platforms. By addressing these critical aspects, this review aims to contribute to the ongoing efforts to achieve long-term control of COVID-19, stimulating the discussion and work on next-generation vaccines capable of facing future waves of infection.

Therapeutic BCG vaccine protects against long COVID: The BATTLE randomized clinical trial

BACKGROUND

Bacillus Calmette-Guérin (BCG) injected during the COVID-19 convalescence period was safe and enhanced recovery from anosmia and dysgeusia in the acute phase.

OBJECTIVES

To report the long-term results of the BATTLE trial, BCG vaccine in adults with mild COVID-19.

METHODS

Design: Double-blind, placebo-controlled, randomized (1:1) clinical trial.

INTERVENTION

BCG intradermal vaccine and placebo.

PATIENTS

A total of 157 BCG and 142 placebo recipients participated in the 6-month follow-up, and 97 BCG and 95 placebo recipients participated in the 12-month follow-up.

MEASUREMENTS

Long COVID symptoms and mechanistic analyses.

RESULTS

BCG reduced hearing problems at 6 months (odds ratio [OR] = 0.26) and sleeping, concentration, memory, and vision problems at 12 months (OR = 0.45, 0.36, 0.38, and 0.36, respectively). Sensitivity analyses confirmed that long COVID-19 symptoms were reduced at the 6- and 12-month follow-ups (p = 0.010 and 0.031, respectively). BCG's crossover interaction paradoxically increased hair loss in women and decreased it in men at 6 months (p = 0.032). BCG immunomodulation is likely mediated through inhibition of Fas ligand expression in the blood and increased induction of IL6, IL10, interferon-induced transmembrane protein 3, and angiotensin-converting enzyme 2 in cultured human macrophages.

CONCLUSION

Long-term follow-up of the BATTLE trial participants revealed that BCG protects against long COVID development if administered within the COVID-19 convalescence period. The response to BCG was subject-specific, including a paradoxical crossover interaction based on sex.

LIMITATIONS

Not tested for previous mycobacterial exposure; loss to follow-up, particularly at 12 months.

Linking COVID-19 and cancer: Underlying mechanism

COVID-19 caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), lead to a global health crisis with a spectrum of clinical manifestations. A potentially vulnerable category for SARS-CoV-2 infection was identified in patients with other medical conditions. Intriguingly, parallels exist between COVID-19 and cancer at the pathophysiological level, suggesting a possible connection between them. This review discusses all possible associations between COVID-19 and cancer. Expression of receptors like angiotensin-converting enzyme 2 (ACE2) and transmembrane protease serine 2 (TMPRSS2) increases COVID-19 susceptibility. SARS-CoV-2 infection might increase cancer susceptibility and accelerate cancer progression through mechanisms involving cytokine storm, tissue hypoxia, impaired T-cell responses, autophagy, neutrophil activation, and oxidative stress. These mechanisms collectively contribute to immune suppression, hindered apoptosis, and altered cellular signaling in the tumor microenvironment, creating conditions favorable for tumor growth, metastasis, and recurrence. Approved vaccines and their impact on cancer patients along-with new clinical trials are also described.

Trained immunity-based vaccines: A vision from the one health initiative

Trained immunity-based vaccines (TIbV or TRIMbV) represent a novel approach to combating infectious diseases. The innate immune system in animals, including humans, exhibits "memory-like" functions. Remarkably, the immunological mechanisms -both epigenetic and metabolic-) underlying this memory enables immune cells to develop defensive and protective outcomes against unspecific pathogenic infections. Under this context, the One Health initiative promotes integrative efforts to combat zoonotic (and anthropozoonotic) diseases, which is critical because 3 of 4 animal infections are transmitted to humans. Therefore, TIbV constitutes a potential affordable approach to control zoonotic pathologies, especially under pandemic scenarios. This review describes the state-of-the-art TIbV and their hurdles, opportunities, and prospects for the One Health initiative to prevent, control, and treat infectious diseases.

BCG-Induced DNA Methylation Changes Improve Coronavirus Disease 2019 Vaccine Immunity Without Decreasing the Risk for Severe Acute Respiratory Syndrome Coronavirus 2 Infection

Background

The BCG vaccine induces trained immunity, an epigenetic-mediated increase in innate immune responsiveness. Therefore, this clinical trial evaluated if BCG-induced trained immunity could decrease coronavirus disease 2019 (COVID-19)-related frequency or severity.

Methods

A double-blind, placebo-controlled clinical trial of healthcare workers randomized participants to vaccination with BCG TICE or placebo (saline). Enrollment included 529 healthcare workers randomized to receive BCG or placebo. Primary analysis evaluated COVID-19 disease frequency, while secondary analysis evaluated coronavirus immunity in a subset of participants. Study enrollment ceased early in December 2020 following introduction of COVID-19-specific vaccines.

Results

Study enrollment was halted early, prior to reaching the targeted recruitment, and was not powered to detect a decrease in COVID-19 frequency. Symptomatic COVID-19 occurred in 21 of 263 and 10 of 266 participants in the BCG and placebo arms, respectively (P = .50, Fisher exact test). Participants vaccinated with BCG, but uninfected with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), demonstrated increased coronavirus vaccine immunity (increase spike-inducible levels of tumor necrosis factor, interleukin 6, and interleukin 1β) 12 months after BCG vaccination compared to participants receiving placebo. Immune responsiveness to SARS-CoV-2 antigens correlated with BCG-induced DNA methylation changes.

Conclusions

Due to early study closure, the study was not powered to evaluate COVID-19 frequency. Secondary analysis demonstrated that 12 months following vaccination, BCG increased coronavirus vaccine immunity compared to those who did not receive BCG. This increase in COVID-19 vaccine immunity correlated with BCG-induced DNA methylation changes.

Evaluating the effect of BCG vaccination for non-specific protection from infection in senior citizens during the COVID-19 pandemic: A randomised clinical trial

OBJECTIVES

The Bacillus Calmette-Guérin (BCG) vaccine may induce non-specific protection against unrelated infections. We tested the effect of BCG on the risk of infections among Danish senior citizens.

METHODS

Single-blinded randomised controlled trial including 1676 volunteers >65 years. Participants were randomised 1:1 to BCG or placebo and followed for 12 months. The primary outcome was acute infection leading to medical contact. Secondary outcomes were verified SARS-CoV-2 infection, self-reported respiratory symptoms, and all-cause hospitalisation. Data was analysed using Cox regression models, estimating hazard ratios (HR) with 95% confidence intervals (CI).

RESULTS

The incidence of acute infection was 52.1 and 58.2 per 100 person-years for BCG and placebo, respectively (HR=0.89, 95% CI=0.78-1.02). There was no effect of BCG on SARS-CoV-2 infections (0.97, 0.75-1.26) or all-cause hospitalisations (1.10, 0.80-1.50), but BCG was associated with more respiratory symptoms (1.21, 1.10-1.33). BCG reduced the incidence of acute infections among participants <75 years (0.82, 0.70-0.95) but not among those >75 years (1.14, 0.88-1.47). In participants, who were COVID-19 vaccinated before enrolment, BCG was associated with lower incidence of acute infections (0.65, 0.50-0.85).

CONCLUSION

BCG did not reduce risk of acute infections among Danish seniors overall, but the effect was modified by age group and COVID-19 vaccination.

TRIAL REGISTRATION

ClinicalTrials.gov (NCT04542330) and EU Clinical Trials Register (EudraCT number 2020-003904-15). Full trial protocol is available at ClinicalTrials.gov.

SUMMARY

In a randomised clinical trial among Danish senior citizens, BCG vaccination did not reduce the overall risk of acute infection, but BCG was associated with reduced risk in participants <75 years and participants who received COVID-19 vaccines prior to enrolment.

The effect of BCG vaccination in the elderly on infectious and non-infectious immune-mediated diseases

OBJECTIVES

Previous research has suggested beneficial heterologous effects of the Bacillus Calmette-Guérin (BCG) vaccine on non-mycobacterial infections and other immune-mediated diseases. During the COVID-19 pandemic, randomized controlled trials BCG-PRIME (n = 5349) and BCG-CORONA-ELDERLY (n = 1907) investigated the impact of BCG on SARS-CoV-2 infections in older individuals. We extended the follow-up in these studies by one year (BCG-Long Term study), to assess the overall effects of BCG vaccination on infectious and immune-mediated diseases in individuals aged over 60.

METHODS

Prior participants were invited to complete a one-year follow-up survey after their completion of the original trial. Data on vaccinations, hospital admissions, infectious episodes, and new medical diagnoses were collected and compared between BCG- and placebo-vaccinated participants. Variables of interest were combined with the previous trial databases and analyzed using relative risks (RR) and an adjusted Cox regression model accounting for participation probability.

RESULTS

The response in the follow-up survey was 60%, including 4238 individuals in the final analysis (2317 had received BCG and 1921 placebo). Incidence and severity of infectious diseases and other diagnoses, including cardiovascular diseases and cancer, did not differ between the groups. The proportion of individuals hospitalized for cardiac arrhythmias after BCG was two-fold higher than reported after placebo (1.6% versus 0.8%, RR 2.0 (95% confidence interval 1.1-3.6)). Cardiac arrhythmia-related hospitalizations were primarily due to exacerbation of pre-existing arrhythmias.

CONCLUSION

The results of the present study confirm that BCG has no relevant effect on non-mycobacterial infectious diseases and other immune-mediated diseases in a population of generally mycobacteria-naïve older Dutch individuals in the two years following vaccination. However, our study suggests that BCG may aggravate pre-existing cardiac arrhythmia, which warrants further investigation.

An Information-Theoretic Method for Identifying Effective Treatments and Policies at the Beginning of a Pandemic

Identifying effective treatments and policies early in a pandemic is challenging because only limited and noisy data are available and biological processes are unknown or uncertain. Consequently, classical statistical procedures may not work or require strong structural assumptions. We present an information-theoretic approach that can overcome these problems and identify effective treatments and policies. The efficacy of this approach is illustrated using a study conducted at the beginning of the COVID-19 pandemic. We applied this approach with and without prior information to the limited international data available in the second month (24 April 2020) of the COVID-19 pandemic. To check if our results were plausible, we conducted a second statistical analysis using an international sample with millions of observations available at the end of the pandemic's pre-vaccination period (mid-December 2020). Even with limited data, the information-theoretic estimates from the original study performed well in identifying influential factors and helped explain why death rates varied across nations. Later experiments and statistical analyses based on more recent, richer data confirm that these factors contribute to survival. Overall, the proposed information-theoretic statistical technique is a robust method that can overcome the challenges of under-identified estimation problems in the early stages of medical emergencies. It can easily incorporate prior information from theory, logic, or previously observed emergencies.

The effect of BCG revaccination on the response to unrelated vaccines in urban Ugandan adolescents (POPVAC C): an open-label, randomised controlled trial

BACKGROUND

Immune responses induced by several important vaccines differ between populations, with reduced responses in low-income and rural settings compared with high-income and urban settings. BCG immunisation boosts immune responses to some unrelated vaccines in high-income populations. We aimed to test the hypothesis that BCG revaccination can enhance responses to unrelated vaccines in Ugandan schoolchildren.

METHODS

We conducted an open-label, randomised controlled trial to compare the effects of BCG revaccination versus no BCG revaccination on the immunogenicity of subsequent unrelated vaccines among adolescents aged 13-17 years who are participants in an urban Ugandan birth cohort study, in which BCG vaccination was documented at birth. Participants were excluded if they had received any of the trial vaccines or related agents when aged 5 years or older. Computer-generated 1:1 randomisation was implemented in REDCap. Participants were excluded if they were concurrently enrolled in other trials; had a clinically significant history of immunodeficiency, or serious psychiatric conditions or moderate to severe acute illnesses; were taking immunosuppressive medications; had allergies to vaccine components, a predisposition towards developing keloid scarring; positive HIV tests or pregnancy tests; were female participants who were lactating; or if they planned to use investigational drugs, vaccines, blood products, or any combination thereof. Trial participants assigned to the BCG revaccination group received the live parenteral BCG-Russia vaccine (Serum Institute of India, Pune, India; 0·1 mL intradermally, right upper arm) at week 0. All participants received yellow fever vaccine (YF-17D; Sanofi Pasteur, Lyon, France; 0·5 mL intramuscularly, left upper arm), live oral typhoid vaccine (Ty21a; PaxVax, London, UK; one capsule per day taken for three alternate days), and quadrivalent virus-like particle human papillomavirus (HPV) vaccine (Merck, Rahway, NJ, USA; 0·5 mL intramuscularly, left upper arm) at week 4; and toxoid vaccines (tetanus-diphtheria; Serum Institute of India; 0·5 mL intramuscularly, left upper arm) and an HPV booster at week 28. An additional HPV vaccination at week 8 was provided to female participants older than 14 years who had not previously been vaccinated. The primary outcomes were yellow fever neutralising antibody titres at 4 weeks post-YF-17D vaccination, Salmonella enterica serovar Typhi (henceforth S Typhi) O-lipopolysaccharide (O:LPS)-specific IgG concentration at 4 weeks post-Ty21a vaccination, and HPV-16 and HPV-18 L1 protein-specific IgG concentration at 4 weeks post-HPV vaccination. Primary outcome assays were conducted at week 8, and at week 52 for tetanus-diphtheria. We conducted an intention-to-treat analysis comparing log-transformed outcomes between trial groups, with results back-transformed to geometric mean ratios (GMRs). The safety population comprised all randomly allocated participants. The trial was registered at the ISRCTN Registry (ISRCTN10482904) and is complete.

FINDINGS

Between Aug 31 and Oct 12, 2020, we screened 376 potential participants for eligibility. We enrolled and randomly allocated 300 participants to the two groups (151 [50%] to the BCG group and 149 [50%] to the no BCG group). 178 (59%) of 300 participants were male and 122 (41%) were female. 142 (91%) of 151 participants in the BCG group and 139 (93%) of 149 in the no BCG group completed follow-up. There was no effect of BCG revaccination, compared with no BCG revaccination, on the response observed for any vaccine. Yellow fever plaque reduction neutralising reference tests (PRNT50) titres (the reciprocal of the last plasma dilution that reduced by 50%) had a GMR of 0·95 (95% CI 0·75-1·19; p=0·62) and PRNT90 (reciprocal of the last plasma dilution that reduced by 90%) had a GMR of 0·94 (0·74-1·19; p=0·60); IgG to S Typhi O:LPS was 0·99 (0·80-1·23; p=0·94); IgG to HPV-16 was 0·97 (0·69-1·35; p=0·85) and to HPV-18 was 1·03 (0·76-1·40; p=0·83); and toxoid-specific IgG for tetanus was 1·13 (0·87-1·47; p=0·36) and was 1·00 (0·87-1·16; p=0·97) for diphtheria. There were no serious adverse events in either group.

INTERPRETATION

We found no evidence that BCG revaccination is an effective strategy to improve immunogenicity of other vaccines in this low-income, urban setting.

FUNDING

UK Medical Research Council.

TRANSLATION

For the Luganda translation of the abstract see Supplementary Materials section.

Research progress of KL-6 in respiratory system diseases

This article comprehensively elucidates the discovery of Krebs von den Lungen-6 (KL-6), its structural features, functional mechanisms, and the current research status in various respiratory system diseases. Discovered in 1985, KL-6 was initially considered a tumor marker, but its elevated levels in interstitial lung disease (ILD) led to its recognition as a relevant serum marker for ILD. KL-6 is primarily produced by type 2 alveolar epithelial cell regeneration. Over the past 30 years since the discovery of KL-6, the number of related research papers has steadily increased annually. Following the coronavirus disease 2019 (COVID-19) pandemic, there has been a sudden surge in relevant literature. Despite KL-6's potential as a biomarker, its value in the diagnosis, treatment, and prognosis varies across different respiratory diseases, including ILD, idiopathic pulmonary fibrosis (IPF), COVID-19, and lung cancer. Therefore, as an important serum biomarker in respiratory system diseases, the value of KL-6 still requires further investigation.

Antecedent and persistent symptoms in COVID-19 and other respiratory illnesses: Insights from prospectively collected data in the BRACE trial

BACKGROUND

Some individuals have a persistence of symptoms following both COVID-19 (post-acute COVID-19 syndrome; PACS) and other viral infections. This study used prospectively collected data from an international trial to compare symptoms following COVID-19 and non-COVID-19 respiratory illness, to identify factors associated with the risk of PACS, and to explore symptom patterns before and after COVID-19 and non-COVID-19 respiratory illnesses.

METHODS

Data from a multicentre randomised controlled trial (BRACE trial) involving healthcare workers across four countries were analysed. Symptom data were prospectively collected over 12 months, allowing detailed characterisation of symptom patterns. Participants with COVID-19 and non-COVID-19 respiratory illness episodes were compared, focussing on symptom severity, duration (including PACS using NICE and WHO definitions), and pre-existing symptoms.

FINDINGS

Compared to those with a non-COVID-19 illness, participants with COVID-19 had significantly more severe illness (OR 7·4, 95%CI 5·6-9·7). Symptom duration meeting PACS definitions occurred in a higher proportion of COVID-19 cases than non-COVID-19 respiratory controls using both the NICE definition (2·5% vs 0·5%, OR 6·6, 95%CI 2·4-18·3) and the WHO definition (8·8% vs 3·7%, OR 2·5, 95%CI 1·4-4·3). When considering only participants with COVID-19, age 40-59 years (aOR 2·8, 95%CI 1·3-6·2), chronic respiratory disease (aOR 5·5, 95%CI 1·3-23·1), and pre-existing symptoms (aOR 3·0, 95%CI 1·4-6·3) were associated with an increased risk of developing PACS. Symptoms associated with PACS were also reported by participants in the months preceding their COVID-19 or non-COVID-19 respiratory illnesses (32% fatigue and muscle ache, 11% intermittent cough and shortness of breath).

INTERPRETATION

Healthcare workers with COVID-19 were more likely to have severe and longer-lasting symptoms than those with a non-COVID-19 respiratory illness, with a higher proportion meeting the WHO or NICE definitions of PACS. Age, chronic respiratory disease, and pre-existing symptoms increased the risk of developing PACS following COVID-19.

BCG vaccination of healthcare workers for protection against COVID-19: 12-month outcomes from an international randomised controlled trial

OBJECTIVES

Bacille Calmette-Guérin (BCG) vaccine has immunomodulatory effects that may provide protection against unrelated infectious diseases. We aimed to determine whether BCG vaccination protects adults against COVID-19.

DESIGN

Phase III double-blind randomised controlled trial.

SETTING

Healthcare centres in Australia, Brazil, the Netherlands, Spain, and the United Kingdom during the COVID-19 pandemic.

PARTICIPANTS

3988 healthcare workers with no prior COVID-19 and no contraindication to BCG.

INTERVENTION

Randomised 1:1 using a web-based procedure to receive a single 0.1 mL intradermal dose of BCG-Denmark (BCG group, n = 1999) or saline (placebo group, n = 1989).

MAIN OUTCOME MEASURES

Difference in incidence of (i) symptomatic and (ii) severe COVID-19 during the 12 months following randomisation in the modified intention to treat (mITT) population (confirmed SARS-CoV-2 naïve at inclusion).

RESULTS

Of the 3988 participants randomised, 3386 had a negative baseline SARS-CoV-2 test and were included in the mITT population. The 12-month adjusted estimated risk of symptomatic COVID-19 was higher in the BCG group (22.6%; 95% confidence interval [CI] 20.6 to 24.5%) compared with the placebo group (19.6%; 95% CI 17.6 to 21.5%); adjusted difference +3.0% points (95% CI 0.2 to 5.8%; p = 0.04). The 12-month adjusted estimated risk of severe COVID-19 (mainly comprising those reporting being unable to work for ≥3 consecutive days) was 11.0% in the BCG group (95% CI 9.5 to 12.4%) compared with 9.6% in the placebo group (95% CI 8.3 to 11.1%); adjusted difference +1.3% points (95% CI -0.7 to 3.3%, p = 0.2). Breakthrough COVID-19 (post COVID-19 vaccination) and asymptomatic SARS-CoV-2 infections were similar in the two groups. There were 18 hospitalisations due to COVID-19 (11 in BCG group, 7 in placebo group; adjusted hazard ratio 1.56, 95% CI 0.60 to 4.02, p = 0.4) and two deaths due to COVID-19, both in the placebo group.

CONCLUSIONS

Compared to placebo, vaccination with BCG-Denmark increased the risk of symptomatic COVID-19 over 12 months among healthcare workers and did not decrease the risk of severe COVID-19 or post-vaccination breakthrough COVID-19.

TRIAL REGISTRATION

ClinicalTrials.gov NCT04327206.

"Glycans in Trained Immunity: Educators of innate immune memory in homeostasis and disease"

Trained Immunity is defined as a biological process normally induced by exogenous or endogenous insults that triggers epigenetic and metabolic reprogramming events associated with long-term adaptation of innate immune cells. This trained phenotype confers enhanced responsiveness to subsequent triggers, resulting in an innate immune "memory" effect. Trained Immunity, in the past decade, has revealed important benefits for host defense and homeostasis, but can also induce potentially harmful outcomes associated with chronic inflammatory disorders or autoimmune diseases. Interestingly, evidence suggest that the "trainers" prompting trained immunity are frequently glycans structures. In fact, the exposure of different types of glycans at the surface of pathogens is a key driver of the training phenotype, leading to the reprogramming of innate immune cells through the recognition of those glycan-triggers by a variety of glycan-binding proteins (GBPs) expressed by the immune cells. β-glucan or mannose-enriched structures in Candida albicans are some of the examples that highlight the potential of glycans in trained immunity, both in homeostasis and in disease. In this review, we will discuss the relevance of glycans exposed by pathogens in establishing key immunological hubs with glycan-recognizing receptors expressed in immune cells, highlighting how this glycan-GBP network can impact trained immunity. Finally, we discuss the power of glycans and GBPs as potential targets in trained immunity, envisioning potential therapeutic applications.

The BCG vaccine and SARS-CoV-2: Could there be a beneficial relationship?

The COVID-19 disease continues to cause complications and deaths worldwide. Identifying effective immune protection strategies remains crucial to address this ongoing challenge. The Bacillus Calmette-Guérin (BCG) vaccine, developed initially to prevent pulmonary tuberculosis, has gained relevance due to its ability to induce cross-protection against other pathogens of the airways. This review summarizes research on the immunological protection provided by BCG, along with its primary clinical and therapeutic uses. It also explores the immunological features of COVID-19, the mechanisms implicated in host cell death, and its association with chronic pulmonary illnesses such as tuberculosis, which has led to complications in diagnosis and management. While vaccines against COVID-19 have been administered globally, uncertainty still exists about its effectiveness. Additionally, it is uncertain whether the utilization of BCG can regulate the immune response to pathogens such as SARS-CoV-2.

Anti-SARS-CoV-2 Nucleocapsid Antibody Positivity Three Years after COVID-19

The accurate identification of individuals without prior infection with severe acute respiratory syndrome coronavirus 2 is pivotal for seroepidemiological studies and vaccine trials. Owing to widespread vaccination against coronavirus disease 2019 (COVID-19), the anti-nucleocapsid antibody continues to serve as a valuable marker for individuals without a history of COVID-19. This study aimed to comprehensively assess anti-nucleocapsid antibody positivity using diverse commercial and in-house immunoassays among individuals who contracted COVID-19 more than three years earlier. We enrolled 44 participants with laboratory-confirmed COVID-19 between January and May 2020 from the Seoul National University Hospital and its community treatment centers. The results showed anti-nucleocapsid antibody positivity ranging from 45.5% to 87.9%, depending on the immunoassay. This study highlights the importance of considering the limited anti-nucleocapsid antibody positivity in individuals, with a history of distant COVID-19, in seroepidemiological or vaccine research.

Research progress in the off-target effects of Bacille Calmette-Guérin vaccine

ABSTRACT

Bacille Calmette-Guérin (BCG) vaccine is designed to provide protection against tuberculosis (TB). However, numerous epidemiological, clinical, and immunological studies have shown that BCG vaccination affects neonatal and infant mortality, which may be related to the reduction of TB-unrelated infections and diseases by BCG vaccine. We aimed to discuss the off-target effects of BCG vaccine on un-TB infections and diseases, as well as the potential mechanism and influencing factors. Literature was retrieved mainly from PubMed using medical subject headings "BCG, variations, and non-specific, heterologous or off-target". Studies have showed that BCG vaccination can prevent various heterologous infections, including respiratory tract infections, leprosy, and malaria, treat viral infections including human papillomavirus and herpes simplex virus infection as immunotherapy, and improve the immune responses as vaccine adjuvant. Besides, BCG vaccine can reduce the recurrence rate of non-muscle-invasive bladder cancer, and may provide protection against autoimmune diseases. These off-target effects of BCG vaccine are thought to be achieved by modulating heterologous lymphocyte responses or inducing trained immunity, which were found to be sex-differentiated and affected by the BCG vaccine strains, sequence or time of vaccination.

Efficacy and outcomes of BCG re-vaccination in COVID-19: a systematic review, meta-analysis, and meta-regression of randomized controlled trials

INTRODUCTION

The Bacillus Calmette-Guerin (BCG) vaccine has a beneficial "off-target" effect that offers heterologous protection against respiratory tract infections by inducing trained immunity. The need for producing antigen-specific COVID-19 vaccines leads to delays in vaccine administration. Current randomized controlled trials (RCTs) report conflicting data on BCG's efficacy in COVID-19 infection.

METHODS

A comprehensive literature search was conducted using major bibliographic databases to identify RCTs evaluating the outcomes of BCG re-vaccination in COVID-19. For dichotomous outcomes, odds ratios (ORs) with 95% CIs were pooled using the DerSimonian-Laird random-effects model. Statistical significance was set at P less than 0.05.

RESULTS

Thirteen RCTs with 13 939 participants (7004 in the BCG re-vaccination group and 6935 in the placebo group) were included. BCG re-vaccination did not lead to a statistically significant difference in the incidence of COVID-19 infection [OR: 1.04; 95% CI: 0.91, 1.19; P=0.56], COVID-19-related hospitalizations [OR: 0.81; 95% CI: 0.38, 1.72; P=0.58), ICU admissions [OR: 0.43; 95% CI: 0.13, 1.46; P=0.18], or mortality [OR: 0.67; 95% CI 0.15, 3.04; P=0.60]. For safety outcomes, BCG re-vaccination led to a significant increase in the local injection site complications [OR: 99.79; 95% CI: 31.04, 320.80; P<0.00001], however, the risk of serious adverse events was similar [OR: 1.19; 95% CI: 0.84, 1.67; P=0.33].

CONCLUSIONS

BCG re-vaccination does not decrease the incidence of COVID-19 infection, COVID-19-related hospitalizations, ICU admissions, COVID-19-related mortality, and serious adverse events; however, it leads to a rise in local injection site complications. Caution should be exercised when overstating BCG's efficacy in COVID-19 prevention.

The Impact of Infant Bacille Calmette-Guérin Vaccination on the Immunogenicity of Other Vaccines: A Randomized Exploratory Study

The effect of the Bacille Calmette-Guérin (BCG) vaccine on the immunogenicity of separately administered serogroup C meningococcal vaccine and other vaccinations was examined in 28 infants randomized to receive BCG at age ≤7 days, at 3 months or after study completion. Immunogenicity of the serogroup C meningococcal vaccine and other routine vaccines might be improved when BCG is administered in early infancy.

Dysregulation of Host-Pathogen Interactions in Sepsis: Host-Related Factors

Sepsis stands as a prominent contributor to sickness and death on a global scale. The most current consensus definition characterizes sepsis as a life-threatening organ dysfunction stemming from an imbalanced host response to infection. This definition does not capture the intricate array of immune processes at play in sepsis, marked by simultaneous states of heightened inflammation and immune suppression. This overview delves into the immune-related processes of sepsis, elaborating about mechanisms involved in hyperinflammation and immune suppression. Moreover, we discuss stratification of patients with sepsis based on their immune profiles and how this could impact future sepsis management.

The association between cytomegalovirus infection and neurodegenerative diseases: a prospective cohort using UK Biobank data

Background

Certain viral infections have been linked to the development of neurodegenerative diseases. This study aimed to investigate the association between cytomegalovirus (CMV) infection and five neurodegenerative diseases, spinal muscular atrophy (SMA) and related syndromes, Parkinson's disease (PD), Alzheimer's disease (AD), multiple sclerosis (MS), and disorders of the autonomic nervous system (DANS).

Methods

This prospective cohort included white British individuals who underwent CMV testing in the UK Biobank from January 1, 2006 to December 31, 2021. A Cox proportional hazard model was utilized to estimate the future risk of developing five neurodegenerative diseases in individuals with or without CMV infection, adjusted for batch effect, age, sex, and Townsend deprivation index in Model 1, and additionally for type 2 diabetes, cancer, osteoporosis, vitamin D, monocyte count and leukocyte count in Model 2. Bidirectional Mendelian randomization was employed to validate the potential causal relationship between CMV infection and PD.

Findings

A total of 8346 individuals, consisting of 4620 females (55.4%) and 3726 males (44.6%) who were white British at an average age of 56.74 (8.11), were included in this study. The results showed that CMV infection did not affect the risk of developing AD (model 1: HR [95% CI] = 1.01 [0.57, 1.81], P = 0.965; model 2: HR = 1.00 [0.56, 1.79], P = 0.999), SMA and related syndromes (model 1: HR = 3.57 [0.64, 19.80], P = 0.146; model 2: HR = 3.52 [0.63, 19.61], P = 0.152), MS (model 1: HR = 1.16 [0.45, 2.97], P = 0.756; model 2: HR = 1.16 [0.45, 2.97], P = 0.761) and DANS (model 1: HR = 0.65 [0.16, 2.66], P = 0.552; model 2: HR = 0.65 [0.16, 2.64], P = 0.543). Interestingly, it was found that participants who were CMV seronegative had a higher risk of developing PD compared to those who were seropositive (model 1: HR = 2.37 [1.25, 4.51], P = 0.009; model 2: HR = 2.39 [1.25, 4.54], P = 0.008) after excluding deceased individuals. This association was notably stronger in males (model 1: HR = 3.16 [1.42, 7.07], P = 0.005; model 2: HR = 3.41 [1.50, 7.71], P = 0.003), but no significant difference was observed in the female subgroup (model 1: HR = 1.28 [0.40, 4.07], P = 0.679; model 2: HR = 1.27 [0.40, 4.06], P = 0.684). However, a bidirectional Mendelian randomization analysis did not find a genetic association between CMV infection and PD.

Interpretation

The study found that males who did not have a CMV infection were at a higher risk of developing PD. The findings provided a new viewpoint on the risk factors for PD and may potentially influence public health approaches for the disease.

Funding

National Natural Science Foundation of China (81873776), Natural Science Foundation of Guangdong Province, China (2021A1515011681, 2023A1515010495).

Quasi-experimental methods for pharmacoepidemiology: difference-in-differences and synthetic control methods with case studies for vaccine evaluation

Difference-in-differences and synthetic control methods have become common study designs for evaluating the effects of changes in policies, including health policies. They also have potential for providing real-world effectiveness and safety evidence in pharmacoepidemiology. To effectively add to the toolkit of the field, however, designs-including both their benefits and drawbacks-must be well understood. Quasi-experimental designs provide an opportunity to estimate the average treatment effect on the treated without requiring the measurement of all possible confounding factors, and to assess population-level effects. This requires, however, other key assumptions, including the parallel trends or stable weighting assumptions, a lack of other concurrent events that could alter time trends, and an absence of contamination between exposed and unexposed units. The targeted estimands are also highly specific to the settings of the study, and combining across units or time periods can be challenging. Case studies are presented for 3 vaccine evaluation studies, showcasing some of these challenges and opportunities in a specific field of pharmacoepidemiology. These methods provide feasible and valuable sources of evidence in various pharmacoepidemiologic settings and can be improved through research to identify and weigh the advantages and disadvantages in those settings. This article is part of a Special Collection on Pharmacoepidemiology.

The global impact of COVID-19 on tuberculosis: A thematic scoping review, 2020-2023

BACKGROUND

This thematic scoping review of publications sought to understand the global impact of COVID-19 on tuberculosis (TB), interpret the scope of resonating themes, and offer policy recommendations to stimulate TB recovery and future pandemic preparedness.

DATA SOURCES

Publications were captured from three search engines, PubMed, EBSCO, and Google Scholar, and applicable websites written in English from January 1, 2020, to April 30, 2023.

STUDY SELECTION

Our scoping review was limited to publications detailing the impact of COVID-19 on TB. Original research, reviews, letters, and editorials describing the deleterious and harmful--yet sometimes positive--impact of COVID-19 (sole exposure) on TB (sole outcome) were included. The objective was to methodically categorize the impacts into themes through a comprehensive review of selected studies to provide significant health policy guidance.

DATA EXTRACTION

Two authors independently screened citations and full texts, while the third arbitrated when consensus was not met. All three performed data extraction.

DATA SYNTHESIS/RESULTS

Of 1,755 screened publications, 176 (10%) covering 39 countries over 41 months met the inclusion criteria. By independently using a data extraction instrument, the three authors identified ten principal themes from each publication. These themes were later finalized through a consensus decision. The themes encompassed TB's care cascade, patient-centered care, psychosocial issues, and health services: 1) case-finding and notification (n = 45; 26%); 2) diagnosis and laboratory systems (n = 19; 10.7%) 3) prevention, treatment, and care (n = 22; 12.2%); 4) telemedicine/telehealth (n = 12; 6.8%); 5) social determinants of health (n = 14; 8%); 6) airborne infection prevention and control (n = 8; 4.6%); 7) health system strengthening (n = 22; 13%); 8) mental health (n = 13; 7.4%); 9) stigma (n = 11; 6.3%); and 10) health education (n = 10; 5.7%).

LIMITATIONS

Heterogeneity of publications within themes.

CONCLUSIONS

We identified ten globally generalizable themes of COVID-19's impact on TB. The impact and lessons learned from the themed analysis propelled us to draft public health policy recommendations to direct evidence-informed guidance that strengthens comprehensive global responses, recovery for TB, and future airborne pandemic preparedness.

BCG vaccination is associated with longitudinal changes in systemic eicosanoid levels in elderly individuals: A secondary outcome analysis

We investigated how BCG vaccination affects the levels of certain eicosanoids, namely Leukotriene B4, 15-epimer of LXA4, prostaglandin F2, Lipoxin A4, Prostaglandin E2 and Resolvin D1 in the plasma of healthy elderly individuals (aged 60-80) before vaccination, one month post-vaccination (M1), and six months post-vaccination (M6). This study is part of the clinical trial "BCG Vaccine Study: Reducing COVID-19 Impact on the Elderly in Indian Hotspots," registered in the clinical trial registry (NCT04475302). While some primary outcomes have been previously reported, this analysis delves into the immunological outcomes. Our findings indicate that BCG vaccination leads to reduced plasma levels of 15-epi-LXA4, LXA4, PGE2, and Resolvin D1 at both M1 and M6. In contrast, there is a notable increase in circulating levels of LTB4 at these time points following BCG vaccination. This underscores the immunomodulatory effects of BCG vaccination and hints at its potential to modulate immune responses by dampening inflammatory reactions.

Late in the US pandemic, multi-dose BCG vaccines protect against COVID-19 and infectious diseases

The Bacillus Calmette-Guérin vaccine has many off-target benefits, including protection from diverse infectious diseases. As SARS-CoV-2 evolved, COVID-19 disease became more transmissible and less lethal. In this Phase III double-blinded, placebo-controlled trial conducted late in the pandemic, we tested at-risk US adults with type 1 diabetes if multi-dose BCG protected against COVID-19 and other infectious disease, co-primary outcomes. From April 2021 to November 2022, Tokyo-strain BCG vaccines provided significant protection against COVID-19 disease (p = 0.023) and strong platform protection against all infectious diseases (p < 0.0001). Over the course of the study, commercial COVID-19 vaccines were rolled out, most of which were mRNA-based. In contrast to the protection afforded by BCG, as reported by others, COVID-19 mRNA vaccine alone provided no protection from COVID-19 disease (p = 0.43). BCG vaccination efficacy was unaffected by concurrent COVID-19 vaccinations; COVID-19 vaccines neither helped nor hindered BCG protection.

Protective interplay: Mycobacterium tuberculosis diminishes SARS-CoV-2 severity through innate immune priming

At the beginning of the COVID-19 pandemic those with underlying chronic lung conditions, including tuberculosis (TB), were hypothesized to be at higher risk of severe COVID-19 disease. However, there is inconclusive clinical and preclinical data to confirm the specific risk SARS-CoV-2 poses for the millions of individuals infected with Mycobacterium tuberculosis (M.tb). We and others have found that compared to singly infected mice, mice co-infected with M.tb and SARS-CoV-2 leads to reduced SARS-CoV-2 severity compared to mice infected with SARS-CoV-2 alone. Consequently, there is a large interest in identifying the molecular mechanisms responsible for the reduced SARS-CoV-2 infection severity observed in M.tb and SARS-CoV-2 co-infection. To address this, we conducted a comprehensive characterization of a co-infection model and performed mechanistic in vitro modeling to dynamically assess how the innate immune response induced by M.tb restricts viral replication. Our study has successfully identified several cytokines that induce the upregulation of anti-viral genes in lung epithelial cells, thereby providing protection prior to challenge with SARS-CoV-2. In conclusion, our study offers a comprehensive understanding of the key pathways induced by an existing bacterial infection that effectively restricts SARS-CoV-2 activity and identifies candidate therapeutic targets for SARS-CoV-2 infection.

Lack of a non-specific protective effect of prior yellow fever vaccination against COVID-19

Live-attenuated virus vaccines, such as yellow fever vaccine, exhibit non-specific immunomodulatory effects, prompting exploration of their potential impact on COVID-19 pandemic. In this retrospective study, we didn’t observe an association between prior yellow fever vaccination with SARS-CoV-2 infection incidence. In the multivariate model, no association was found with COVID-19 prognosis.

Effect of BCG vaccination against Mycobacterium tuberculosis infection in adult Brazilian health-care workers: a nested clinical trial

BACKGROUND

The effectiveness of BCG vaccine for adult pulmonary tuberculosis remains uncertain. In this study, we aimed to evaluate the effect of vaccination with BCG-Denmark to prevent initial and sustained interferon-γ release assay conversion in Brazilian health-care workers.

METHODS

This substudy is a nested randomised controlled trial embedded within the BRACE trial (NCT04327206). Specifically, this substudy enrolled Brazilian health-care workers (aged ≥18 years) from three sites in Brazil (Manaus, Campo Grande, and Rio de Janeiro) irrespective of previously receiving BCG vaccination. Participants were excluded if they had contraindications to BCG vaccination, more than 1 month of treatment with specific tuberculosis treatment drugs, previous adverse reactions to BCG, recent BCG vaccination, or non-compliance with assigned interventions. Those eligible were randomly assigned (1:1) to either the BCG group (0·1 mL intradermal injection of BCG-Denmark [Danish strain 1331; AJ Vaccines, Copenhagen]) or the placebo group (intradermal injection of 0·9% saline) using a web-based randomisation process in variable-length blocks (2, 4, or 6), and were stratified based on the study site, age (<40, ≥40 to <60, ≥60 years), and comorbidity presence (diabetes, chronic respiratory disease, cardiac condition, hypertension). Sealed syringes were used to prevent inadvertent disclosure of group assignments. The QuantiFERON-TB Gold (QFT) Plus test (Qiagen; Hilden, Germany) was used for baseline and 12-month tuberculosis infection assessments. The primary efficacy outcome was QFT Plus conversion (≥0·35 IU/mL) by 12 months following vaccination in participants who had a negative baseline result (<0·35 IU/mL).

FINDINGS

Between Oct 7, 2020, and April 12, 2021, 1985 (77·3%) of 2568 participants were eligible for QFT Plus assessment at 12 months and were included in this substudy; 996 (50·2%) of 1985 were in the BCG group and 989 (49·8%) were in the placebo group. Overall, 1475 (74·3%) of 1985 participants were women and 510 (25·7%) were men, and the median age was 39 years (IQR 32-47). During the first 12 months, QFT Plus conversion occurred in 66 (3·3%) of 1985 participants, with no significant differences by study site (p=0·897). Specifically, 34 (3·4%) of 996 participants had initial QFT conversion in the BCG group compared with 32 (3·2%) of 989 in the placebo group (risk ratio 1·09 [95% CI 0·67-1·77]; p=0·791).

INTERPRETATION

BCG-Denmark vaccination did not reduce initial QFT Plus conversion risk in Brazilian health-care workers. This finding underscores the need to better understand tuberculosis prevention in populations at high risk.

FUNDING

Bill & Melinda Gates Foundation, the Minderoo Foundation, Sarah and Lachlan Murdoch, the Royal Children's Hospital Foundation, Health Services Union NSW, the Peter Sowerby Foundation, SA Health, the Insurance Advisernet Foundation, the NAB Foundation, the Calvert-Jones Foundation, the Modara Pines Charitable Foundation, the United Health Group Foundation, Epworth Healthcare, and individual donors.

TRANSLATION

For the Portuguese translation of the abstract see Supplementary Materials section.

Bacille Calmette-Guérin vaccination to prevent febrile and respiratory illness in adults (BRACE): secondary outcomes of a randomised controlled phase 3 trial

Background

Bacille Calmette-Guérin (BCG) vaccination has off-target (non-specific) effects that are associated with protection against unrelated infections and decreased all-cause mortality in infants. We aimed to determine whether BCG vaccination prevents febrile and respiratory infections in adults.

Methods

This randomised controlled phase 3 trial was done in 36 healthcare centres in Australia, Brazil, the Netherlands, Spain, and the United Kingdom. Healthcare workers were randomised to receive BCG-Denmark (single 0.1 ml intradermal injection) or no BCG in a 1:1 ratio using a web-based procedure, stratified by stage, site, age, and presence of co-morbidity. The difference in occurrence of febrile or respiratory illness were measured over 12 months (prespecified secondary outcome) using the intention-to-treat (ITT) population. This trial is registered with ClinicalTrials.gov, NCT04327206.

Findings

Between March 30, 2020, and April 1, 2021, 6828 healthcare workers were randomised to BCG-Denmark (n = 3417) or control (n = 3411; no intervention or placebo) groups. The 12-month adjusted estimated risk of ≥1 episode of febrile or respiratory illness was 66.8% in the BCG group (95% CI 65.3%-68.2%), compared with 63.4% in the control group (95% CI 61.8%-65.0%), a difference of +3.4 percentage points (95% CI +1.3% to +5.5%; p 0.002). The adjusted estimated risk of a severe episode (defined as being incapacitated for ≥3 consecutive days or hospitalised) was 19.4% in the BCG group (95% CI 18.0%-20.7%), compared with 18.8% in the control group (95% CI 17.4%-20.2%) a difference of +0.6 percentage points (95% CI -1.3% to +2.5%; p 0.6). Both groups had a similar number of episodes of illness, pneumonia, and hospitalisation. There were three deaths, all in the control group. There were no safety concerns following BCG vaccination.

Interpretation

In contrast to the beneficial off-target effects reported following neonatal BCG in infants, a small increased risk of symptomatic febrile or respiratory illness was observed in the 12 months following BCG vaccination in adults. There was no evidence of a difference in the risk of severe disease.

Funding

Bill & Melinda Gates Foundation, Minderoo Foundation, Sarah and Lachlan Murdoch, the Royal Children's Hospital Foundation, Health Services Union NSW, the Peter Sowerby Foundation, SA Health, the Insurance Advisernet Foundation, the NAB Foundation, the Calvert-Jones Foundation, the Modara Pines Charitable Foundation, the UHG Foundation Pty Ltd, Epworth Healthcare, the National Health and Medical Research Council, the Swiss National Science Foundation and individual donors.

BCG Vaccination-Associated Lower HbA1c and Increased CD25 Expression on CD8+ T Cells in Patients with Type 1 Diabetes in Ghana

BCG vaccination affects other diseases beyond tuberculosis by unknown-potentially immunomodulatory-mechanisms. Recent studies have shown that BCG vaccination administered during overt type 1 diabetes (T1D) improved glycemic control and affected immune and metabolic parameters. Here, we comprehensively characterized Ghanaian T1D patients with or without routine neonatal BCG vaccination to identify vaccine-associated alterations. Ghanaian long-term T1D patients (n = 108) and matched healthy controls (n = 214) were evaluated for disease-related clinical, metabolic, and immunophenotypic parameters and compared based on their neonatal BCG vaccination status. The majority of study participants were BCG-vaccinated at birth and no differences in vaccination rates were detected between the study groups. Notably, glycemic control metrics, i.e., HbA1c and IDAA1c, showed significantly lower levels in BCG-vaccinated as compared to unvaccinated patients. Immunophenotype comparisons identified higher expression of the T cell activation marker CD25 on CD8+ T cells from BCG-vaccinated T1D patients. Correlation analysis identified a negative correlation between HbA1c levels and CD25 expression on CD8+ T cells. In addition, we observed fractional increases in glycolysis metabolites (phosphoenolpyruvate and 2/3-phosphoglycerate) in BCG-vaccinated T1D patients. These results suggest that neonatal BCG vaccination is associated with better glycemic control and increased activation of CD8+ T cells in T1D patients.

Specific and off-target immune responses following COVID-19 vaccination with ChAdOx1-S and BNT162b2 vaccines-an exploratory sub-study of the BRACE trial

BACKGROUND

The COVID-19 pandemic led to the rapid development and deployment of several highly effective vaccines against SARS-CoV-2. Recent studies suggest that these vaccines may also have off-target effects on the immune system. We sought to determine and compare the off-target effects of the adenovirus vector ChAdOx1-S (Oxford-AstraZeneca) and modified mRNA BNT162b2 (Pfizer-BioNTech) vaccines on immune responses to unrelated pathogens.

METHODS

Prospective sub-study within the BRACE trial. Blood samples were collected from 284 healthcare workers before and 28 days after ChAdOx1-S or BNT162b2 vaccination. SARS-CoV-2-specific antibodies were measured using ELISA, and whole blood cytokine responses to specific (SARS-CoV-2) and unrelated pathogen stimulation were measured by multiplex bead array.

FINDINGS

Both vaccines induced robust SARS-CoV-2 specific antibody and cytokine responses. ChAdOx1-S vaccination increased cytokine responses to heat-killed (HK) Candida albicans and HK Staphylococcus aureus and decreased cytokine responses to HK Escherichia coli and BCG. BNT162b2 vaccination decreased cytokine response to HK E. coli and had variable effects on cytokine responses to BCG and resiquimod (R848). After the second vaccine dose, BNT162b2 recipients had greater specific and off-target cytokine responses than ChAdOx1-S recipients.

INTERPRETATION

ChAdOx1-S and BNT162b2 vaccines alter cytokine responses to unrelated pathogens, indicative of potential off-target effects. The specific and off-target effects of these vaccines differ in their magnitude and breadth. The clinical relevance of these findings is uncertain and needs further study.

FUNDING

Bill & Melinda Gates Foundation, National Health and Medical Research Council, Swiss National Science Foundation and the Melbourne Children's. BRACE trial funding is detailed in acknowledgements.

Trained immunity-inducing vaccines: Harnessing innate memory for vaccine design and delivery

While the efficacy of many current vaccines is well-established, various factors can diminish their effectiveness, particularly in vulnerable groups. Amidst emerging pandemic threats, enhancing vaccine responses is critical. Our review synthesizes insights from immunology and epidemiology, focusing on the concept of trained immunity (TRIM) and the non-specific effects (NSEs) of vaccines that confer heterologous protection. We elucidate the mechanisms driving TRIM, emphasizing its regulation through metabolic and epigenetic reprogramming in innate immune cells. Notably, we explore the extended protective scope of vaccines like BCG and COVID-19 vaccines against unrelated infections, underscoring their role in reducing neonatal mortality and combating diseases like malaria and yellow fever. We also highlight novel strategies to boost vaccine efficacy, incorporating TRIM inducers into vaccine formulations to enhance both specific and non-specific immune responses. This approach promises significant advancements in vaccine development, aiming to improve global public health outcomes, especially for the elderly and immunocompromised populations.

Symptoms 6 months following SARS-CoV-2 infection in Nepali women

In Nepal, over 1 million individuals have tested positive for SARS-CoV-2. We sought to describe the frequency of nonrecovery from this infection at 6 months and associated symptoms. We conducted a retrospective cohort study of 6142 women who had positive and negative PCR tests for this infection 6 months previously at 3 institutions in Kathmandu. In telephone interviews women provided information on 22 symptoms and their intensities, health status and history, and functional status. Of 3732 women who had tested PCR positive, 630 (16.9%) reported that they were unrecovered. These 630 unrecovered women were distinguished statistically from the 3102 recovered women by more frequent histories of allergies, rheumatoid disease, BCG immunization, Covid vaccination, strep throat and recent URIs, and both weight gain and weight losses of more than 5 kg in the 6 months following testing, and stressful events in the preceding year. Fatigue, pain, difficulty remembering, shortness of breath, heat and cold intolerance and unrefreshing sleep were reported in 41.9% to 10.5% of these 630 unrecovered women. Six months after confirmed SARS-CoV-2 infection 16.9% of Nepali women have long-COVID manifested as an immune, metabolic, and hormonal systems disruptive and dysfunction syndrome.

The Influence of Cross-Reactive T Cells in COVID-19

Memory T cells form from the adaptive immune response to historic infections or vaccinations. Some memory T cells have the potential to recognise unrelated pathogens like severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and generate cross-reactive immune responses. Notably, such T cell cross-reactivity has been observed between SARS-CoV-2 and other human coronaviruses. T cell cross-reactivity has also been observed between SARS-CoV-2 variants from unrelated microbes and unrelated vaccinations against influenza A, tuberculosis and measles, mumps and rubella. Extensive research and debate is underway to understand the mechanism and role of T cell cross-reactivity and how it relates to Coronavirus disease 2019 (COVID-19) outcomes. Here, we review the evidence for the ability of pre-existing memory T cells to cross-react with SARS-CoV-2. We discuss the latest findings on the impact of T cell cross-reactivity and the extent to which it can cross-protect from COVID-19.

Host Genetic Background Influences BCG-Induced Antibodies Cross-Reactive to SARS-CoV-2 Spike Protein

Mycobacterium bovis Bacillus Calmette-Guérin (BCG) protects against childhood tuberculosis; and unlike most vaccines, BCG broadly impacts immunity to other pathogens and even some cancers. Early in the COVID-19 pandemic, epidemiological studies identified a protective association between BCG vaccination and outcomes of SARS-CoV-2, but the associations in later studies were inconsistent. We sought possible reasons and noticed the study populations often lived in the same country. Since individuals from the same regions can share common ancestors, we hypothesized that genetic background could influence associations between BCG and SARS-CoV-2. To explore this hypothesis in a controlled environment, we performed a pilot study using Diversity Outbred mice. First, we identified amino acid sequences shared by BCG and SARS-CoV-2 spike protein. Next, we tested for IgG reactive to spike protein from BCG-vaccinated mice. Sera from some, but not all, BCG-vaccinated Diversity Outbred mice contained higher levels of IgG cross-reactive to SARS-CoV-2 spike protein than sera from BCG-vaccinated C57BL/6J inbred mice and unvaccinated mice. Although larger experimental studies are needed to obtain mechanistic insight, these findings suggest that genetic background may be an important variable contributing to different associations observed in human randomized clinical trials evaluating BCG vaccination on SARS-CoV-2 and COVID-19.

Seroprevalence of anti-SARS-CoV-2 IgG antibodies pre- and post-COVID-19 vaccination in staff members of Bandar Abbas Children's Hospital

BACKGROUND

Healthcare workers (HCWs) have a higher risk of contracting coronavirus disease 2019 (COVID-19) compared to the general population due to their frontline role and direct contact with the infected patients. Accordingly, they were among the first groups to receive vaccination against COVID-19. A higher risk of COVID-19 infection may also exist among hospital staff members other than HCWs. In this study, we assessed the seroprevalence of anti-severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) IgG pre- and post-COVID-19 vaccination in hospital staff members.

METHODS

This cross-sectional study included 228 staff members of Bandar Abbas Children's Hospital, Bandar Abbas, Iran, who were recruited from 2020 to 2021. Staff members were vaccinated with vector and inactivated vaccines. Anti-SARS-CoV-2 spike protein IgG was measured in their blood samples pre- and post-COVID-19 vaccination.

RESULTS

Of the 228 hospital staff members evaluated in this study (mean age: 37.59 ± 8.70 years), 204 (89.5%) were female and 210 (92.1%) were HCWs. Only one staff member was not vaccinated, the rest received one dose (99.6%), and 224 (98.7%) two doses. Vector vaccines were administered to 71.4% of staff members and 72.9% of HCWs. Anti-SARS-CoV-2 IgG antibody was positive in 8.8% of staff members before vaccination, 9.3% after the first dose, and 50% after the second dose. The corresponding percentages were 9.5%, 9.5%, and 48.8% in HCWs. Being a HCW was not associated with the seroprevalence of anti-SARS-CoV-2 IgG after the second dose; however, multivariable binary logistic regression analysis revealed that the interval between two vaccine doses (adjusted odds ratio [aOR] = 0.595, 95% confidence interval [CI] 0.434; 0.816, P = 0.001) and age (aOR = 1.062, 95% CI 1.021; 1.105, P = 0.003) were associated with seroprevalence.

CONCLUSIONS

After receiving a second dose of vector or inactive virus vaccines, our hospital's staff members and HCWs had a seroprevalence of anti-SARS-CoV-2 IgG antibodies of around 50%. Seroprevalence increased with increasing age and shorter intervals between doses.

Implications of vaccine non-specific effects on licensure of new vaccines

Immune memory was for a long time thought to be an exclusive feature of the adaptive immune system. Emerging evidence has shown that the innate immune system may exhibit memory which has been termed as trained immunity or innate immune memory. Trained immunity following vaccination may produce non-specific effects leading to reduction in morbidity and mortality from heterologous pathogens. This review looked at trained immunity as a mechanism for vaccine induced non-specific effects, mechanisms underlying trained immunity and known vaccine non-specific effects. A discussion is also made on the implications these vaccine non-specific effects may have on overall risk-benefit ratio evaluation by National Medicines Regulatory Authorities (NMRAs) during licensure of new vaccines. Epigenetic remodeling and "rewiring" of cellular metabolism in the innate immune cells especially monocytes, macrophages, and Natural Killer (NK) cells have been suggested to be the mechanisms underlying trained immunity. Trained immunity in other innate cells has largely remained elusive up to date. Non-specific effects have been extensively documented with Bacille Calmette-Guerin (BCG), measles vaccine and oral polio vaccine but it remains unclear if other vaccines may exhibit similar effects. All known vaccine non-specific effects have come from observations in epidemiological studies conducted post-vaccine licensure and roll out in target populations. It remains to be seen if early identification of non-specific effects especially those with protective benefits during the clinical development of new vaccines may contribute to the overall risk-benefit ratio evaluation during licensure by NMRAs.

Using BCG Vaccine to Enhance Nonspecific Protection of Health Care Workers During the COVID-19 Pandemic: A Randomized Controlled Trial

BACKGROUND

The BCG (Bacillus Calmette-Guérin) vaccine can induce nonspecific protection against unrelated infections. We aimed to test the effect of BCG on absenteeism and health of Danish health care workers (HCWs) during the coronavirus disease 2019 (COVID-19) pandemic.

METHODS

A single-blinded randomized controlled trial included 1221 HCWs from 9 Danish hospitals. Participants were randomized 1:1 to standard dose BCG or placebo. Primary outcome was days of unplanned absenteeism. Main secondary outcomes were incidence of COVID-19, all-cause hospitalization, and infectious disease episodes.

RESULTS

There was no significant effect of BCG on unplanned absenteeism. Mean number of days absent per 1000 workdays was 20 in the BCG group and 17 in the placebo group (risk ratio, 1.23; 95% credibility interval, 0.98-1.53). BCG had no effect on incidence of COVID-19 or all-cause hospitalization overall. In secondary analyses BCG revaccination was associated with higher COVID-19 incidence (hazard ratio [HR], 2.47; 95% confidence interval [CI], 1.07-5.71), but also reduced risk of hospitalization (HR, 0.28; 95% CI, .09-.86). The incidence of infectious disease episodes was similar between randomization groups (HR, 1.09; 95% CI, .96-1.24).

CONCLUSIONS

In this relatively healthy cohort of HCWs, there was no overall effect of BCG on any of the study outcomes.

CLINICAL TRIALS REGISTRATION

NCT0437329 and EU Clinical Trials Register (EudraCT number 2020-001888-90).