More research emerged this week to possibly support the use of the Bacillus Calmette-Guerin (BCG) tuberculosis vaccine as a tool in the fight against coronavirus.
Researchers found that countries where many people have received the vaccine have had less mortality from Covid-19.
While this does not mean that BCG in any way reduces the risk of serious disease from a coronavirus infection, it does fit in with other research suggesting that BCG can increase human immunity in general and may help against coronavirus.
The World Health Organization has warned against using the BCG vaccine against coronavirus until more is known, but teams around the world are studying the possibility that it can help.
Luis Escobar of Virginia Polytechnic Institute and colleagues used existing information to investigate whether countries without a national BCG vaccination program have higher coronavirus mortality. To make a fair comparison, they accounted for factors such as population density, access to health care and responses to Covid-19.
They found a strong correlation between BCG vaccination use and reduced Covid-19 mortality in socially similar European countries. Each 10% increase in the BCG index, indicating the degree of universal BCG vaccination, was associated with a 10.4% reduction in Covid-19 mortality, they reported in the journal Proceedings of the National Academy of Sciences.
“What distinguishes our work is that we were very careful about removing variables,” said Carolina Barillas-Mury, a prominent investigator with the National Institute of Health who worked on the study. “When we removed them, if this wasn’t true, the association should have disappeared. Instead of disappearing, it became stronger and stronger – more clear,” she told CNN.
Non-specific immunity to vaccine
The finding is “remarkable, but not enough to establish causation,” the team wrote. It is not enough to show that the BCG vaccine in any way protected people against coronavirus.
The BCG vaccine is used more than 100 years old in many countries, including the United States, and has been associated with reduced total mortality in infants and children. There is strong evidence to suggest that the vaccine provides non-specific immunity – protection in addition to tuberculosis. The effects of the vaccine on adults have been inconsistent.
Other researchers have suggested that vaccines against polio and measles, mumps and rubella can provide similar protection against deadly infections, including coronavirus.
The researchers warn that clinical trials are needed to prove the vaccine’s impact on serious Covid-19. The initial clinical trials abroad are currently focused on healthcare professionals in the front lines of the fight against coronavirus.
A $ 10 million grant from the Bill and Melinda Gates Foundation in May reinforced clinical trials in Australia, Spain and the Netherlands, which will reach 10,000 healthcare professionals.
Dr. Denise Faustman, director of immunobiology at Massachusetts General Hospital and associate professor of medicine at Harvard Medical School, hopes to begin clinical trials with her team in Boston as soon as possible.
Faustman has been studying the effects outside the target of the BCG vaccine for several years. “BCG boosts the innate immune system,” Faustman said, “so when you see any infectious disease you can fight it faster.”
She says this is one of a number of new studies that have supported the potential of the BCG vaccine as a tool in the fight against coronavirus.
“The signal is really strong that countries with previous BCG vaccination have protection against incidence and mortality,” said Faustman, who added that there is even a possibility that the BCG vaccine may increase the effect of a coronavirus-specific vaccine, when created.
If the BCG vaccine’s protection against the severity of coronavirus continues with further research, it could have significant public health implications.
Most Asian countries have universal BCG vaccination programs, and the United States does not. According to the CDC, BCG is generally not recommended in the United States, as the risk of infection is low, the efficacy of the vaccine may vary and potentially interfere with TB screening.
“It is possible that some of the social distance rolling strategies taken by Asian countries to restart their economies may not be effective in North America and Western European countries and may lead to a second wave of infections,” the Escobar team wrote.
The vaccine may be administered in countries that do not currently have a universal vaccination program.
“The nice thing is that it is only given once. It is potentially quite feasible to scale up vaccine production, if it works and it is safe,” Dr. Wafaa El-Sadr, Columbia University professor of epidemiology and head of ICAP, a global health program.
Dr. William Schaffner, an infectious disease specialist at Vanderbilt University School of Medicine, who previously described using the BCG vaccine against coronaviruses as “a Hail Mary passport,” warned against putting too much stock in observational data collected across countries because all countries assess Covid-19 cases and deaths in the same way.
“It’s really a new and provocative strategy to try to prevent this disease. We need all the help we can get,” said Schaffner, who agrees that clinical trials are needed to really evaluate the power of the BCG vaccine to fight coronavirus.
“What we’ve seen is previews of upcoming attractions, as they say in cinema,” Schaffner said. “Let’s wait for the movie.”
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