A century-old vaccine fails to protect against Covid

At the beginning of the pandemic, researchers initiated trials to test the efficacy of a decades-old tuberculosis vaccine against the coronavirus. 

However, due to the introduction of new Covid vaccines, the trial failed to attract the expected number of participants, and no significant impact on Covid was observed. Recently, scientists reported that the vaccine, B.C.G., which is recognized for enhancing the immune system, did not prevent Covid infections among healthcare workers. 

Nonetheless, the trial was shorter and smaller than initially planned, and the researchers stated that the findings did not entirely negate the possibility of other potential benefits associated with the vaccine.

The New England Journal of Medicine has published the largest clinical trial to date that examined the potential of the B.C.G. vaccine in preventing Covid infections. Originally developed in the early 1900s to combat tuberculosis, this vaccine has since been found to provide protection against various diseases, including respiratory illnesses. 

The trial, which began in March 2020, during the early stages of the pandemic when effective Covid treatments were unavailable and the idea of a vaccine was a distant hope, involved health care workers. The aim was to investigate whether the old vaccine could be repurposed to save lives. After six months of receiving the B.C.G. vaccine, there was no significant difference between the two groups of health care workers. The trial found that 14.7 percent of the vaccinated group developed symptomatic Covid infections, while 12.3 percent of the group who received saline placebo shots got sick.

 During the trial, five participants from each group required hospitalization, and unfortunately, one participant who received the placebo shots passed away. However, the differences between the two groups were not statistically significant. 

The rapid development of mRNA vaccines made it impossible to complete the B.C.G. trial as planned since healthcare workers were prioritized to receive the new mRNA shots. Dr. Nigel Curtis, the chief investigator of the trial and a professor of pediatric infectious diseases at the University of Melbourne, praised the mRNA vaccines as "an absolute miracle of modern science." Nonetheless, he acknowledged that from a trial perspective, it was challenging. 

The B.C.G. trial initially intended to follow 10,000 participants in five countries, namely Australia, the Netherlands, Spain, Britain, and Brazil, for a year. However, due to limitations, the recent report only covers the results of 4,000 adults who were followed for six months.

Dr. Nigel Curtis, the chief investigator of the B.C.G. trial and a professor of pediatric infectious diseases at the University of Melbourne, hailed the mRNA vaccines as "an absolute miracle of modern science." However, he acknowledged that the B.C.G. trial's perspective was quite disastrous. To determine whether the B.C.G. vaccine could protect against severe Covid outcomes, including hospitalizations and deaths, a more extensive trial would have been necessary. 

Although the vaccine failed to prevent mild or moderate Covid infections among health care workers, B.C.G. remains widely used in the developing world to reduce infant mortality rates. Studies have shown that the vaccine not only protects infants against tuberculosis but also trains their immune system to respond to other pathogens, reducing the incidence of respiratory illnesses and other diseases. Dr. Curtis confirmed that the trial's conclusion was accurate: B.C.G. does not offer protection against mild or moderate Covid infections in health care workers.