Countries vaccinating their children against tuberculosis at birth have much lower Covid-19 infections and deaths, compared to nations that don’t, a new study suggests.
According to a paper published in the Proceedings of the National Academy of Sciences of the United States of America (PNAS), countries with widespread Bacillus Calmette-Guerin (BCG) vaccination programmes like Kenya have a much lower rate.
Researchers compared the BCG jab's popularity in several countries with each nation's coronavirus infections and deaths and found a clear link between the vaccine and a lower mortality rate from Covid-19.
The research comes as scientists around the world launch trials investigating the possible benefits of BCG vaccination amid the coronavirus pandemic. For example, from the findings, countries with a stronger BCG vaccination policy had significantly lower Covid-19 deaths per one million residents. More broadly, countries with current BCG vaccination had lower deaths as compared to countries with lack of, or interrupted, BCG vaccination.
The researchers compared Covid-19 mortality in states in the US without BCG vaccination with those that were the main points of entry in Mexico and Brazil, as these two countries have current BCG vaccination programmes.
They found out that Covid-19 mortality in the states of New York, Illinois, Louisiana, Alabama, and Florida (unvaccinated) was significantly higher at 14.274 per cent than states from BCG-vaccinated countries including Rio de Janeiro, and Sao Paulo in Brazil; Mexico State and Mexico City in Mexico.
“This is remarkable, considering that three states from Latin America have much higher population densities than the North American states analysed, including New York,” states the study.
“There is still a direct potential benefit in vaccinating with BCG against tuberculosis, however, whether a tuberculosis vaccine would be seen as a viable form of long-term immune system modification for use against Covid-19, is still questionable,” Prof Ben Neuman, chairman of Biological Sciences at Texas A&M University-Texarkana.
The BCG vaccine, which is one of the oldest given to babies protects against tuberculosis and has other health benefits, including helping a person's immune system to fend off respiratory infections
In Kenya, the vaccine is given at birth along with the oral polio vaccine. It is administered as an injection on the left forearm into the dermis, the outer layer just under the skin. Globally, it is being given to around 130 million babies every year to protect them from TB.
Vaccination of newborns and infants prevents disseminated childhood tuberculosis and reduces the risk of pulmonary TB by about 50 per cent.
Many countries, including Kenya, initiated national BCG vaccination in the middle of the 20th century with variable levels of coverage using different BCG strains. “There is ample epidemiological evidence that BCG vaccination has broad protective effects that are not specific to tuberculosis infection. For instance, in 1927, Swedish children who received BCG vaccination at birth had a mortality rate almost threefold lower than unvaccinated children,” says the study.
A general reduction in neonatal mortality linked to BCG vaccination was also reported in children in Guinea Bissau, mainly due to fewer cases of neonatal sepsis, respiratory infection, and fever.
“Our current understanding of broad immune protection mediated by trained immunity and the epidemiologic evidence of long-lasting protection from viral infections of the respiratory tract, conferred by BCG vaccination, offer a rational biological basis for the potential protective effect of BCG vaccination from severe coronavirus disease,” says the study.
The publication, however, does not include extensive statistical analysis, and the World Health Organisation has cautioned about the lack of research regarding BCG vaccination against Covid-19 infection.
Studies into whether BCG can help fend off Covid-19 are ongoing in the Netherlands and Australia, but until these results are available, the researchers of the latest study say even transient immunity could help fight the pandemic.
“Further work is needed to assess the effect of BCG. There have been shortages of BCG vaccines, so if confirmed this will help for the planning of the next pandemic,” says the study.
