A new study found evidence of an old vaccine protecting elderly people against respiratory infections. For some reason, the BCG vaccine could provide effective preventive action beyond tuberculosis. It is yet to be demonstrated against COVID-19.
The effective preventive action of the bacille Calmette-Guerin or BCG vaccine against respiratory infections was revealed in a clinical trial. Investigators observed the statistical difference in infection rates between elderlies vaccinated and elderlies unvaccinated with BCG. The vaccine could also delay the onset of infection longer. However, the preventive action was not yet demonstrated against the novel coronavirus. They published their findings in the journal Cell.
BCG Vaccine: The Old Vaccine for Tuberculosis
Some vaccines used in vaccination programs are very old. But they remain effective in protecting children and adults from infectious diseases. One of these old vaccines is the BCG, specifically developed for tuberculosis or TB. But there are recommendations before immunizing a person with this vaccine. It is vital to get the maximum effect from it.
According to the US Centers for Disease Control and Prevention, a federal agency, the BCG vaccine is normally used in countries with high prevalence rates of TB. It is intended to prevent childhood TB meningitis and miliary disease. As such, the US and other countries with lower prevalence rates do not recommend this vaccine. If a person contracted TB in those nations, they are treated with anti-TB medications.
Since it is recommended for children, most people living in countries with high TB prevalence that conduct BCG vaccination are likely immunized. They have a higher chance of resisting severe forms of TB, compared to those who are not immunized. But it does not provide excellent protection against the common forms of TB. Still, the vaccine is crucial as it can save lives from rapid, fatal TB infections.
In some cases, people vaccinated with BCG may develop latent tuberculosis infection or LTBI. Clinicians must carefully assess the patient before treatment. This is to rule out other possibilities that can mimic LTBI. LTBI in BCG-vaccinated people can happen due to several reasons, including HIV infection, close contact with TB-positive person, and intake of immunosuppressants.
According to the World Health Organization (WHO) of the United Nations, the global coverage of the BCG vaccine in WHO regions was 89% in 2018. The coverage rates per region in that year were 80% in Africa, 91% in the Americas, 91% in Southeast Asia, 93% Europe, 87% in the Eastern Mediterranean, and 96% in Western Pacific. In 2017, the global coverage was also 89% while the regional coverage rates were 80% in Africa, 91% in the Americas, 92% in Southeast Asia, 92% in Europe, 87% in the Eastern Mediterranean, and 97% in Western Pacific.
BCG Vaccine Boosted Immunity of Elderlies against Respiratory Infections
Older adults tend to be more prone to infectious diseases, such as COVID-19 and influenza. But a recent study suggested that those who were vaccinated with BCG might be resilient. Researchers at the Radboud University Medical Center, a teaching hospital in the Netherlands, and the National and Kapodistrian University of Athens found observational evidence in a clinical trial.
"Two years ago, we started the ACTIVATE study, with the aim of showing whether BCG vaccination could protect against infections in vulnerable elderly people. Patients over 65 years of age who were admitted to hospital were randomized 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," said Mihai Netea, a professor of experimental internal medicine at Radboud.
The trial is a part of the ACTIVATE study, which started before the COVID-19 pandemic. A total of 198 elderly participants qualified for the double-blind, placebo-controlled, randomized clinical trial. The placebo group was comprised of 78 participants while the BCG group had 72 participants. The average age of the placebo group was 79.6 years while the average age of the BCG group was 79.9 years.
Results showed that the average weeks for an infection to start after BCG vaccination were 16 in the BCG group, compared to the 11 average weeks in the placebo group. In a 12-month follow-up, the incidence of a new respiratory infection was statistically lower in the BCG group at 25%, compared to 42.3% in the placebo group. This was also observed in the incidence of the second infection at 6.9% in the BCG group and 11.5% in the placebo group. It was apparent even in the incidence of the third infection at 1.4% in the BCG group and 3.8% in the placebo group.
Per infection type, the BCG group had 4.2% of community-acquired pneumonia, compared to 10.3% in the placebo group. The BCG group had zero hospital-acquired pneumonia but the placebo group at 2.6%. In all respiratory infections, the BCG group had an 8.3% incidence rate while the placebo group had a 30.1% incidence rate. Curiously, urinary tract infections were higher in the BCG group at 11.1% compared to 7.7% in the placebo group. Since those infections targeted a different organ system, the protective effect may have failed to apply.
When researchers checked the side effects, no statistical difference was detected. Evangelos J. Giamarellos-Bourboulis, a coordinator of the study, emphasized the clear protective effect against respiratory infections. Across the board, BCG-vaccinated elderlies had 75% fewer respiratory infections than those who received a placebo. The figures showed that the vaccine goes beyond protecting people from TB. For unknown reasons, the immune system of BCG-vaccinated elderlies performed well in overcoming respiratory infections, despite their age.
Concerning COVID-19, researchers could not confirm the protective effect against the novel disease. The observation must be demonstrated in a different study. Their study had a low prevalence of COVID-19, which failed to generate substantial data. But they noted that BCG vaccination is safe for the elderly.
Several studies are being prepared to investigate the BCG vaccine and its possible benefits against COVID-19. If the vaccine can lower the severity of COVID-19, there may be further research to explain the mechanism.