BCG, or Bacillus Calmette–Guérin vaccine, is a vaccine documented to have a preventive effect against pulmonary tuberculosis, TB meningitis, and disseminated tuberculosis. The vaccine is almost a hundred years old and it works against all forms of tuberculosis bacteria.
Infants usually receive this vaccine soon after birth, especially in endemic regions for TB and leprosy. In some countries, BCG vaccinations are also given to healthcare professionals, if they haven’t received the vaccine before.
Recently, studies have been performed on the use of BCG for other respiratory infections. One such study was started two years ago at Radboud University MEdical center and National and Kapodistrian University of Athens by Professor Mihai Netea and team.
Method of study
The study, called ACTIVATE, ((A randomized Clinical trial for enhanced Trained Immune responses through Bacillus Calmette-Guérin VAccination to prevent infections of the Elderly), is a randomized, double-blind clinical trial conducted in Athens. This study was performed from September 2017 to August 2019 on 198 subjects.
Initially, 202 subjects enrolled in the study by Prof Netea’s team but 4 withdrew leaving behind 198 subjects for the study. Subjects were elderly individuals hospitalized for different reasons. These subjects were divided into two groups; the vaccination group and the placebo group.
The researchers injected both groups with similar-looking injections on the day of their discharge from the hospital, even though only one group received the BCG vaccination. According to the researchers, the subjects were followed up thoroughly and none of them were lost to follow-up, post-intervention.
However, they did note that the last follow-up was supposed to be in August of 2020, but due to the COVID-19 pandemic, the researchers derived conclusions from the preliminary studies and published the results in The Cell.
Results of the study
They concluded that the BCG vaccine decreased the incidence of new infections in the elderly and majorly decreased the incidence of respiratory infections.
Researchers also noted that the vaccination group suffered from a new infection approximately 16 weeks after the vaccination whereas the placebo group was affected by the 11th week. They found a massive difference in the incidence of new infections among both groups.
Overall, they found 42.3% of placebo group subjects were found to have a new infection but only 25% of the vaccination group subjects were affected. According to Metea and collaborators, the increased difference in time and percentage of subjects with regards to the incidence of new infections was majorly seen with respiratory infections of viral origin.
Hence concluding that the most beneficial aspects of the BCG vaccine could be seen against respiratory infections of (probable) viral origin.
Furthermore, inspired by the COVID-19 pandemic, the researchers tried to link the use of BCG against the SARS-Cov-2 virus that has plagued the world recently. However, they found contradicting results. Even though BCG increases innate immune responses leading to increased inflammation that is the hallmark of COVID-19, it also has an antiviral effect and can reduce viral loads of SARS-Cov-2 in the body.
Hence, researchers concluded that longer, more detailed studies need to be performed on the use of the BCG vaccine for the prevention of COVID-19.