Potential usage of the BCG vaccine’s effect on preventing SARS-CoV-2 infection
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Reviewed by Dat Tien Nguyen, B.A, ScM.
Translated by An Duc Thien Le |
Posted on May 29th, 2023
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The bacille Calmette-Guerin (BCG) vaccine had been widely used to prevent tuberculosis. It has been observed that BCG helps reduce the risk of respiratory infections in adults. The off-target effect might be a result of the epigenetic changes made to immune cells which might be pro-inflammatory and accelerate the clearance of SARS-CoV-2. Aiming to utilize this immunomodulatory effect, a study, funded by the Bill and Melinda Gates Foundation, had investigated the usage of BCG in preventing COVID-19.
The study included 3988 healthcare workers working in Australia, Brazil, Spain, the United Kingdoms, and the Netherlands. Approximately 80% of these participants have direct contact with patients. They were randomly assigned to be intradermally injected with either a saline placebo or 0.1 mL of BCG containing between 2 to 8 × 105 colony-forming units of the Denmark strain. After 6 months of monitoring, the researchers concluded that the BCG vaccine neither reduced the risk of symptomatic COVID-19, severe disease, nor hospitalization. This finding contributes to a conflicting discussion making up multiple studies that have found a protective effect or no effect of the BCG vaccine. The inconsistency between different studies were explained to be the heterogeneity in BCG strain used, dose administered, and other demographic factors.
The clinical trial included 66 children between the age of 4 and 8 years old who were diagnosed with chronic sinusitis because they have experienced 2 of the following symptoms for at least 12 weeks before enrolling into the study: nasal congestion, nasal discharge, facial pain, pressure, or cough. 66.7% of the study participants were diagnosed with asthma, and 46% experienced food allergy during their infancy. The patients were randomly selected to be treated with either mometasone with 0.9% sodium chloride or just the 0.9% sodium chloride. The intranasal solution was administered once a day with an atomizer for 12 weeks. Clinical effectiveness was assessed using the Sinus and Nasal Quality of Life Survey (SN-5), and sampling of the nasopharynx was performed for microbiome characterization and detection of innate lymphoid cells (ILC). The researchers found that mometasone significantly improved the quality of life, enhanced the microbiome richness, and reduced the amount of pro-inflammatory ILC3. There was no significant difference in the rate of adverse events between the 2 groups.
The study included 3988 healthcare workers working in Australia, Brazil, Spain, the United Kingdoms, and the Netherlands. Approximately 80% of these participants have direct contact with patients. They were randomly assigned to be intradermally injected with either a saline placebo or 0.1 mL of BCG containing between 2 to 8 × 105 colony-forming units of the Denmark strain. After 6 months of monitoring, the researchers concluded that the BCG vaccine neither reduced the risk of symptomatic COVID-19, severe disease, nor hospitalization. This finding contributes to a conflicting discussion making up multiple studies that have found a protective effect or no effect of the BCG vaccine. The inconsistency between different studies were explained to be the heterogeneity in BCG strain used, dose administered, and other demographic factors.
The clinical trial included 66 children between the age of 4 and 8 years old who were diagnosed with chronic sinusitis because they have experienced 2 of the following symptoms for at least 12 weeks before enrolling into the study: nasal congestion, nasal discharge, facial pain, pressure, or cough. 66.7% of the study participants were diagnosed with asthma, and 46% experienced food allergy during their infancy. The patients were randomly selected to be treated with either mometasone with 0.9% sodium chloride or just the 0.9% sodium chloride. The intranasal solution was administered once a day with an atomizer for 12 weeks. Clinical effectiveness was assessed using the Sinus and Nasal Quality of Life Survey (SN-5), and sampling of the nasopharynx was performed for microbiome characterization and detection of innate lymphoid cells (ILC). The researchers found that mometasone significantly improved the quality of life, enhanced the microbiome richness, and reduced the amount of pro-inflammatory ILC3. There was no significant difference in the rate of adverse events between the 2 groups.