The BCG vaccine, which is frequently given to children to prevent tuberculosis, is safe to give to the elderly, and can protect them against various infections, according to a study which says it may have a broad, stimulating effect on the human immune system. However the study, published in the journal Cell, cautioned that it is unclear whether the vaccine can prevent COVID-19 in the older sections of the population.
The scientists, including those from Radboud University Medical Center in the Netherlands, showed that elderly people benefit from the vaccine by an effect called "trained immunity." In the research, they assessed 198 elderly people who were given either a placebo or the BCG vaccine upon discharge from the hospital.
According to the scientists, the ACTIVATE study had already started before the corona pandemic. "Two years ago we started the ACTIVATE study, with the aim of showing whether BCG vaccination could protect against infections in vulnerable elderly people," said study co-author Mihai Netea from Radboud University Medical Center. "Patients over 65 years of age who were admitted to hospital were randomised to receive BCG or placebo vaccination at their discharge. We followed them for a year to see if BCG could protect them against a broad range of infections," Netea said. Although most protection seems to have been against respiratory infections of (probably) viral origin, the scientists said whether or not BCG also works against COVID-19 has not yet been demonstrated. Several studies are underway that look specifically at the effects of BCG on COVID-19, they added. According to the researchers, only these follow-up studies can provide clarity as to whether BCG vaccination can also protect against infections with the novel coronavirus.
"In addition to the clear effect of BCG vaccination on infections in general, the most important observation was that BCG could mainly protect against respiratory infections," said Evangelos J. Giamarellos-Bourboulis, another co-author of the study. "BCG-vaccinated elderly people had 75 per cent fewer respiratory infections than the elderly who received placebo," he added.